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newmisty

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smooth

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did u touch it and give it that smooth touch before sendoff?
Nah, I was dispatching on shore. Directing movements into different shore tanks.
 

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chair.jpg
 

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A woman assembled the chair
 

newmisty

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An M.C. Escher cutting board!

e7002a579ad7d3a393b4afe703e4bd09.jpg
 

newmisty

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Introduction: Sound Deadening Box With Living Hinges

I have a chilling unit that was overly loud for the space in which it lives, so I decided I needed to make a sound deadening box. Since I was making a box, I wanted it to be a little more interesting than just a box. In order to reduce the alignment issues with making a box out of six sides, I decided to make four of the sides one piece, and have them fold-up into place with living hinges. Technically two of the hinges only get used once, during assembly, but the final one lives on in use.

There are two main concepts to this instructable: sound deadening enclosures, and living hinges.

TipQuestionComment
Step 1: Sound Deadening: the Tortuous Path

Sound deadening requires forcing sound waves to pass through a tortuous
path from their source to the outside, such that they are damped away before making it to the outside. You could just build a fully sealed box so no sound could escape, but often times the equipment that makes noise also requires ventilation. A note: the walls of the box may still vibrate, sending out their own noise.The goal here is not to completely remove the sound, but to reduce it significantly. The tortuous path allows air flow, but kills off the annoying short frequency sound waves.

TipQuestionComment
Step 2: Living Hinges

The living hinges were created by cutting HDPE sheet on a CNC router with a 90 degree chamfer tool. The thickness of material left behind was about 0.015". In order to achieve this thickness I faced down the bed of the cnc router. I took some test cuts (shown in the second image) to find a reasonable thickness of the hinge. You'll note that chamfer tool I used was of large diameter 1.25" and had some thickness at the point. This results in a small gap at the corners.

The goal of a living hinge is to make it as thin as possible while maintaining enough strength for the application. The reason for a thin hinge is that you want to minimize the stress during bending. Stress is due to strain (streching/compressing). When the hinge bends the inside compresses and the outside stretches, between the middle of them there is a point of zero strain, this is the neutral axis. The thicker the hinge, the further the outer edges are from this neutral axis, and the more the outer edges strain (stretch/compress). The larger the strain, the larger the stress, and the more likely the hinge is to crack or fail.

TipQuestionComment
Step 3: CNC Routing the Box

After doing some sample cuts I cut the actual box. Here you can see it is folded up and holding shape decently.

TipQuestionComment
Step 4: Machining the Self-aligning Slot.

The chiller had a hose coming out to utilize the chilled working fluid and I needed to make an exit that also sealed up around the hose. I utilized an angle cutter to cut a V-groove such that the closing piece (let's call it the seal door) would seal up nicely.

On the CNC router I first roughed out the slot with an endmill. I then programmed the angle cutter routine to cut midway through the thickness of the sheet material. This resulted in a nice v-groove visible in the first image.

On a vertical knee milling machine I took the seal door I had cut on the router and I then cut the male portion of the v-groove. I used the same angle cutter but came down and cut on either side of the midway line. Image two shows the cutting process.

Finally, testing the fit in figures three and four we can see that the v-groove male and female components managed to align nearly seamlessly.

TipQuestionComment
Step 5: Assemble the Box.

Finally the box was assembled, the internal supports were installed, and the entire system had vibration damping foam glued into place. Initially I though a very high bond tape might work to adhering the damping foam to the HDPE, but that was not the case. Instead I used some standard hot-glue to stick the foam to the hdpe. Finally, the box is held closed with 90 degree latches.
 

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Every week I stop by to have coffee with Two guys who own a company selling HVAC parts and equipment. They have been around for about 60 years or so. These guys have owned the company for about 30 years. They move 20+ million a year.

This time after coffee was over, I shut the door to the office and told them. "If your ever looking to retire and sell the company, just keep me in the back of your head. It is something I would be very good at and am Interested in. I will never screw the other owner over and I will work very hard." Anway they didn't laugh at me.

One owner is 66 and his wife is pulling on his arm to retire. Long long shot. There are others at the company way more qualified to take over, but they are all in there 50s. They have one young kid would would also be an awesome owner, but I don't know if he will ask them. I would also be interested in being a partner with that kid. He is very sharp, works hard, and would not screw you over.
 

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Every week I stop by to have coffee with Two guys who own a company selling HVAC parts and equipment. They have been around for about 60 years or so. These guys have owned the company for about 30 years. They move 20+ million a year.

This time after coffee was over, I shut the door to the office and told them. "If your ever looking to retire and sell the company, just keep me in the back of your head. It is something I would be very good at and am Interested in. I will never screw the other owner over and I will work very hard." Anway they didn't laugh at me.

One owner is 66 and his wife is pulling on his arm to retire. Long long shot. There are others at the company way more qualified to take over, but they are all in there 50s. They have one young kid would would also be an awesome owner, but I don't know if he will ask them. I would also be interested in being a partner with that kid. He is very sharp, works hard, and would not screw you over.
I don't know how their business is set up or how serious you are about it, but here is something you may want to consider:
You may want to consider buying a right of first refusal for a part or all of the business from them. Spend a couple grand plus have an attorney draw up the papers. Because you just never know. They would get money for nothing out of the deal and you would have a great ace in the hole. Even the contract itself could be worth something if you, for whatever reason, wanted out.

The reason I suggest this is that I will kick myself for the rest of my life for not doing just that for a piece of land adjoining mine. I had been after the guy to buy the place for years but he wouldn't budge. Eventually he got in some financial and mental troubles and one day I got a notice in my mail of a hearing for a zoning change application for that property. The guy had sold it without even listing it to a developer for almost nothing- a small fraction of what it was worth.

A right of first refusal would have been a life changer for me whether I would have bought the place or not.

Something to think about.
 

Uglytruth

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^^^ I bought my side lot for that reason. Bought house & lot was for sale. I was a new home owner & money was tight. THe couple next door got a divorce & put the house up for sale. I was on the phone with him & did a land contract deal. We agreed on a price. When he had the papers drawn up there was some legal crap that he had to charge interest. So he lowered the land price to make it close to the same so he got the same amount or a little more. (very strange law in a zero interst like we have now). Put a down payment on it & made 1 payment a year for $1200 due April 15th. Worked out great for both of us. My other neighbor has asked me to sell him half or a strip or whatever I would part with. We both use it if we have parties. Neighbors for 30 + years & never a problem about anything.
 

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First big score of the year. Every box packed to the brim with the good stuff and all new in box. Back late nights listing. Gave the guy$1000 over what we agreed on. This would all be in the landfill.

IMG_2982.jpg
 
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newmisty

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newmisty

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First big score of the year. Every box packed to the brim with the good stuff and all new in box. Back late nights listing. Gave the guy$1000 over what we agreed on. This would all be in the landfill.

View attachment 245549
What can I say? Go Davy!
 

newmisty

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wonder where he came up with those clamps?
They're a thing, I've seen em before but when ai saw em said, "I need to get educated" Times like these I get that sad feeling when I think of Silver and realize he won't ever be posting again.
 

newmisty

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newmisty

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wonder where he came up with those clamps?
Let's face it Taz, it's just one of those refined folks tools ya know?, Not a go to implement for us rough and tumble types.
Spring Mitre Clamps
https://images-na.ssl-images-amazon.com/images/I/91bmpPq%2BnzL.jpg[\img]

Pricey model
https://hardwickandsons.com/products/ulmia-spring-miter-clamp-set-50-pc-set

Cheap model
[ATTACH=full]246937[/ATTACH]

About this item
When you making picture frames,moldings,wood trim work,and any compound miter,the biggest trouble in gluing up mitered corners is keeping them from opening up.Now, it is time to give up those cumbersome and expensive parallel clamps. The professional Feiyang Miter Spring Clamps provides you with the ideal and cost effective mitered corners clamping tool to help you get your project get done in a more efficient manner.
You can use the miter spring pliers to easily open the sharp tip, just place the spring clamp onto the mitered corner you need to secure, then release the clamp so the tips pierce into the wood to hold the parts together. It can be done in just a few seconds.Then,let the glue dry or brad nails the corner joints together.
Unlike other available spring clamps, the uniquely designed tip is designed to pierce the wood,so that there is minimal visible evidence of the clamps being used after you remove them. This prevents the clamp clip from cutting, pushing, or tearing on the wood, thereby Leaves appearance flaws that are difficult to repair. Although they will leave small impressions in the wood, but they can be filled or sanded out in finishing.
The miter clamps are designed with no gaps,can be applied for pocket-sized projects,and spread up to approximately 2 inches,so they will cover most trim sizes. They will return to its original shape and strength every time.
Great for any compound miter. If you are a woodworking enthusiasts,contractors,carpenters or craft hobbyists,you will love this tool.

https://www.amazon.com/Feiyang-Clamps-Woodworking-Picture-Moldings/dp/B07V7TQBD3/ref=asc_df_B07V7TQBD3?tag=bngsmtphsnus-20&linkCode=df0&hvadid=79989588794310&hvnetw=s&hvqmt=e&hvbmt=be&hvdev=m&hvlocint=&hvlocphy=&hvtargid=pla-4583589115441176&psc=1
 

Attachments

  • Screenshot_2022-02-27-20-39-38-977.jpg
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glockngold

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engineear

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Let's face it Taz, it's just one of those refined folks tools ya know?, Not a go to implement for us rough and tumble types.
Spring Mitre Clamps

Pricey model

Cheap model
View attachment 246937

About this item
When you making picture frames,moldings,wood trim work,and any compound miter,the biggest trouble in gluing up mitered corners is keeping them from opening up.Now, it is time to give up those cumbersome and expensive parallel clamps. The professional Feiyang Miter Spring Clamps provides you with the ideal and cost effective mitered corners clamping tool to help you get your project get done in a more efficient manner.
You can use the miter spring pliers to easily open the sharp tip, just place the spring clamp onto the mitered corner you need to secure, then release the clamp so the tips pierce into the wood to hold the parts together. It can be done in just a few seconds.Then,let the glue dry or brad nails the corner joints together.
Unlike other available spring clamps, the uniquely designed tip is designed to pierce the wood,so that there is minimal visible evidence of the clamps being used after you remove them. This prevents the clamp clip from cutting, pushing, or tearing on the wood, thereby Leaves appearance flaws that are difficult to repair. Although they will leave small impressions in the wood, but they can be filled or sanded out in finishing.
The miter clamps are designed with no gaps,can be applied for pocket-sized projects,and spread up to approximately 2 inches,so they will cover most trim sizes. They will return to its original shape and strength every time.
Great for any compound miter. If you are a woodworking enthusiasts,contractors,carpenters or craft hobbyists,you will love this tool.

Weren't those in the movie, 50 shades of gray?
 

newmisty

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Jesus,
If I actually get a successful 90° trim joint I am patting myself on the back.
"Caulk & paint make a carpenter what he ain't!"
 

gringott

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Its all in the spackling and caulking.
 

davycoppitt

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Second Load of the year. HVAC company closing owner retiring. Stop by after work. "Few guys looked at all the parts and said they would call me back with an offer." I got 5k in my pocket....... "I like cash"

Took the day off work tomorrow to make more loads with a pickup. He still has shelves full.

IMG_1583.jpg

IMG_1582.jpg
 

hammerhead

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Is there typically a lot of inventory on hand in a shop?
 

davycoppitt

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Is there typically a lot of inventory on hand in a shop?
All over the place. Our shop only keeps refer,pipe,fittings,Ect. This place above had been open for 30 years. Guessing this stuff just accumulated over the years and was never installed or was van stock. Residential keep allot more on hand than commercial.

Some shops don’t even own the parts on the van. The wholesaler owns the parts. When it is used on the van the company is billed.
 

hammerhead

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All over the place. Our shop only keeps refer,pipe,fittings,Ect. This place above had been open for 30 years. Guessing this stuff just accumulated over the years and was never installed or was van stock. Residential keep allot more on hand than commercial.

Some shops don’t even own the parts on the van. The wholesaler owns the parts. When it is used on the van the company is billed.
Give us a Storage Wars styled estimate if you can. Just don't use the character Dave's figuring. He'd price a single sock without a match at 3/4 price of a full pair.
 

davycoppitt

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Give us a Storage Wars styled estimate if you can. Just don't use the character Dave's figuring. He'd price a single sock without a match at 3/4 price of a full pair.
No clue on this one too much stuff. There are some nice control boards in the lot.
 

newmisty

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Second Load of the year. HVAC company closing owner retiring. Stop by after work. "Few guys looked at all the parts and said they would call me back with an offer." I got 5k in my pocket....... "I like cash"

Took the day off work tomorrow to make more loads with a pickup. He still has shelves full.

View attachment 247315
View attachment 247316
Wowzers. Your playing your hand to perfection! Well done.
 

newmisty

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Gratification time after some repairs and touch up
Screenshot_2022-03-03-14-20-25-359.jpg
Screenshot_2022-03-03-14-20-14-343.jpg
Screenshot_2022-03-03-14-20-19-831.jpg
Screenshot_2022-03-03-14-20-07-467.jpg
 

newmisty

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The World’s Biggest Excavator in Action (LIEBHERR R 9800 Excavator Loading Trucks)
 

newmisty

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Foundations
JLC Classic
Tips for Crack-Free Concrete Slabs
Prepping the base and proper layout of control joints are as important as placing and finishing
By Gabe Martel

LOGIN OR REGISTER TO DOWNLOAD THE PDF VERSION OF THIS ARTICLE. (519.69 KB)

Our industry prides itself on quality, both in materials and workmanship. I doubt if any tradesman wakes up in the morning and says to himself, "Today I think I'll include some defects in my work." So why do we accept uncontrolled cracks in concrete slabs as unavoidable? It's a result that no one wants and no one wants to explain, especially to an angry client.


We even have a cliche we use to excuse the phenomenon: "Concrete does two things — it gets hard, and it cracks." But I disagree with that claim. In fact, as a commercial construction superintendent, I have poured 15,000-square-foot slabs containing 260 cubic yards of concrete without a single crack. And I do nothing different than what thousands of other commercial contractors do every day.

Residential concrete doesn't usually need to meet the same quality requirements as most commercial concrete, but nevertheless, you can eliminate uncontrolled cracking in your slabs using the techniques and principles I will describe. If you're pouring your own slabs, this information is essential. If you are a general contractor or builder, you can use this information to more effectively supervise and assist your subcontractor. True, the concrete work may legally be within the subcontractor's scope of work, but it's your project, and there's precious little to be done if the slab comes out poorly. Better to take care of problems before they happen. If I had to summarize the secret to good concrete work in one word, it would be "consistency." For a successful outcome, you must exercise the same level of care at every stage of the process — design, preparing the subgrade, placing, finishing, and curing.

Prepping the Base
If the subgrade settles after you've poured the slab, you increase the likelihood of a crack. It seems obvious, but this is the cause of far too many problems. Several things can contribute to subgrade settlement, but the two prime offenders are soils with different bearing capacity across the area of the slab and improper compaction of the subgrade.

Always make sure the soil is free of topsoil and organic matter. If you have any doubt about the bearing capacity of the soil you're building on, check with the local building department or other area builders. If you're still not sure, get the soil tested. The few hundred dollars you'll pay for soil analysis and a compaction test is nothing compared to going back and fixing a failed foundation.

As the subgrade elevation is being established, make sure that the soil is uniformly and properly compacted (see "Soil Compaction Basics," 3/94). Compaction will be expressed as a percentage at optimal moisture content (usually 95% or greater), and it's worth verifying. If you decide not to do a compaction test, at least run the plate tamper or jumping jack until there is very little impression left with each successive pass. It is imperative that soil be compacted in lifts, ideally about 6 inches at a time and never more than 10 inches. If you attempt to compact greater depths, the surface will look good but the soil underneath will remain uncompacted and will settle eventually.

Also, check for uniform bearing capacity of the subgrade. Has the excavator tossed a few buckets of sand into one corner because he excavated just a little too deep the first time around? Will one corner of the slab rest on rock while the remainder is over sand? Better to correct that now by replacing questionable fill with suitable soils that will behave like the rest of the subgrade when properly compacted. What constitutes a suitable soil will vary with local conditions. If you are in doubt, get a professional opinion.

Optimal moisture content happens in a narrowly defined range, so while you may need to add water to dry soils for compaction, take care not to add too much. Sometimes, due to unpredictable weather conditions and routine difficulties with grading and drainage, residential sites get too wet before compaction can take place. What constitutes too wet will vary with soil types, but it doesn't have to be muddy to be too wet. If you see evidence of pumping action in the soil or near-liquefaction of the soil in the vicinity of compaction equipment, you must stop and correct this condition. Your choices are limited at this point: Either wait for the soil to dry out or over-excavate and replace it.

A properly prepared subgrade should be uniformly compacted across the full area of the slab, leveled to within 1/2 inch.
A properly prepared subgrade should be uniformly compacted across the full area of the slab, leveled to within 1/2 inch.
Flat on the bottom. It's helpful to picture your slab upside down. If it's almost as smooth on the bottom as it is on the top, the battle is half won. If it looks like a crater on the moon, then your crack has already begun. Soil must be graded to the same level across the full width of the slab.

A properly prepared subgrade should be uniformly compacted across the full area of the slab, leveled to within 1/2 inch. Your subgrade should be level within 1/2 inch (that's a 12.5% variation in your slab thickness on a 4-inch slab). Where subgrade elevation is inconsistent, then the slab will vary in thickness. This variation will cause it to cure unevenly, which will stress the concrete, increasing the likelihood of a crack.

Contraction joints control the location of shrinkage cracks. They can be hand-tooled, cut with a saw, or formed with proprietary joint material.
Contraction joints control the location of shrinkage cracks. They can be hand-tooled, cut with a saw, or formed with proprietary joint material.
Laying Out Contraction Joints
The shape of the slab can greatly affect cracking. An inside corner, for example, is a pressure point and, as far as the concrete is concerned, a great place to crack. Try to divide your slab into symmetrical squares using contraction joints (also called control joints) rather than creating irregular shapes with lots of re-entrant corners. Contraction joints can be hand-tooled right after the bleed water leaves the surface, cut with a saw right after finishing, or formed in the wet concrete using one of the proprietary plastic or metal joint materials. No matter how you make them, all contraction joints work the same way. By creating an intentionally weakened point in the slab, stress from the inevitable shrinkage (as a result of drying or temperature changes) is relieved in a predictable, controlled manner.

A contraction joint should be one-fourth the depth of the slab, or 1 inch in a 4-inch slab. Any less, and it may not function as designed; any more, and you will unnecessarily weaken the slab, risking vertical displacement of the concrete if the subgrade should move.

When laying out a slab, keep in mind that squares are better than rectangles. If you must use a rectangle, make sure the long side is not more than 1 1/2 times the short side. Where it isn't possible to avoid closely spaced re-entrant corners, additional steel reinforcing may help control cracks.

When laying out contraction joints on a typical 4-inch residential slab, 8- to 12-foot spacing is reasonable. Under ideal conditions, spacing up to about 15 feet between joints may be possible.

Fiberboard expansion joint material permits the slab to move independently of the wall.
Fiberboard expansion joint material permits the slab to move independently of the wall.
For a finished appearance at the slab edge, score the fiberboard on a table saw so the top 1/2 inch can be easily snapped off after the pour. Then finish the joint with sealant.
For a finished appearance at the slab edge, score the fiberboard on a table saw so the top 1/2 inch can be easily snapped off after the pour. Then finish the joint with sealant.
Expansion Joints
If the slab is contained by walls, you must provide expansion joints (also known as isolation joints) around the inside perimeter of the foundation to allow the slab to move independently of the wall. The same thing holds true for structural columns — if they are inside the area of the slab, they should be surrounded with expansion joints.

Residential expansion joints are often made with 1/2-inch-thick fiberboard strips. The material can be flush with the surface of the slab if appearance is no concern. For a more finished look, run the length of fiberboard on a table saw to score it 1/2 inch below the top edge (which will be at the surface elevation) so you can easily remove the top 1/2 inch after the pour. Then use a caulk to seal the slab edge.

Remember that the slab must be isolated from the footing, too. Either sand or 15# felt between the slab and footing works well as a bond breaker.

Breaking the bond between the footing and the slab with felt paper or sand will help prevent cracking as the slab moves.
Breaking the bond between the footing and the slab with felt paper or sand will help prevent cracking as the slab moves.
Placing the Steel
Proper placement of reinforcement is critical. At the very least, reinforcing mesh, pipes, and cables should be suspended so that none lie on the bottom of the poured slab. Wire mesh should be in the middle of the slab if it is to do its job properly. Pipe or conduit laid directly on the ground will dramatically weaken the slab; it has the same effect as scoring a ceramic tile before snapping it. However, that same conduit suspended with 1 inch of concrete underneath will have no effect.

Placing rebar and pipes so concrete can flow underneath them prevents stress risers.
Placing rebar and pipes so concrete can flow underneath them prevents stress risers.
Make use of steel or plastic rebar chairs to get the rebar in the right place. Do not use brick, because it will pull moisture out of the surrounding concrete too quickly and create a stress point.

When It's Time for Concrete
Measure the exact volume of concrete required, then add 10% as a buffer. If you underestimate and have to call for a short load, not only do you waste time, but you may get cracks. Make sure the concrete supplier will have the trucks needed to supply your project without having to wait for an hour between loads. Excessive delay can result in a hot load. If the mix comes out of the chute hot, then send it back.

Although few residential contractors use them, slump tests ensure that the concrete coming out of the truck is not too wet.
Although few residential contractors use them, slump tests ensure that the concrete coming out of the truck is not too wet.
If better flow is needed, add a superplasticizer.
If better flow is needed, add a superplasticizer.
Slump. Proper water content is one of the most important elements of good quality concrete; adding water to concrete to make it flow has a measurable negative result. A slab mix should not have a slump greater than 3 to 4 inches. If smoother flow is required, add superplasticizer, which gives the effect of a 6- to 8-inch slump without weakening the mix.

Placing and Screeding
Concrete is actually a delicate material until it has fully cured. How you treat it during placement is crucial to your success. To avoid segregating the aggregate from the cement paste, never drop concrete more than 6 feet, use the proper concrete tools (not steel rakes), and don't drag or vibrate the concrete into place. If the soil is particularly dry or you're working in hot, windy weather, you should wet the subgrade, but not enough to create mud or leave standing water. In cold weather, do not place concrete on frozen ground.

Concrete should be bull-floated as soon as it has been screeded.
Concrete should be bull-floated as soon as it has been screeded.
Bleed water will begin to appear soon after, but make sure it's gone before finishing begins.
Bleed water will begin to appear soon after, but make sure it's gone before finishing begins.
Make sure you have sufficient manpower on site to maintain continuity in placing the concrete. If placing a slab takes too long, the first concrete placed will begin to set up well before the last concrete placed. This makes it difficult to finish the slab in one continuous process.

Finishing
Make sure concrete is screeded and bull-floated as it's placed, but don't allow finishing to begin until the bleed water has disappeared. If bleed water is worked into the concrete while finishing, the surface will be weakened. For the same reason, don't allow finishers to add water in an attempt to ease finishing.

To keep the job moving, it's a good idea to hand-float the slab perimeter as the concrete is placed.
To keep the job moving, it's a good idea to hand-float the slab perimeter as the concrete is placed.
A well-organized, well-timed, uninterrupted work flow is essential. Hand-trowelling the perimeter along walls and around obstacles as concrete is being placed is a good way to start.

All bleed water should have left the surface before any handfinishing or power-trowelling begins.
All bleed water should have left the surface before any handfinishing or power-trowelling begins.
Even with a power trowel on the job, some hand-finishing is necessary around obstructions.
Even with a power trowel on the job, some hand-finishing is necessary around obstructions.
Have the power trowel fueled up and ready to go before you need it. If you exercise a little patience before power trowelling is begun, you can avoid displacing the softer concrete and causing potential low spots in the finished slab (Figure 9).

If there is any chance of freezing, blankets are used to protect the subgrade before placing the slab.
If there is any chance of freezing, blankets are used to protect the subgrade before placing the slab.
The fresh concrete is then covered for at least three days.
The fresh concrete is then covered for at least three days.
Curing
Don't forget to take care during the curing stage. Initially, the temperature will rise quickly, peak, and then start to drop. This process is stressful on a new slab and can cause failures. Wet curing keeps the slab from drying out too fast during this process. Cover a fresh slab with a layer of burlap immediately after finishing, and keep it wet with a lawn sprinkler for at least three days (ideally seven days). Or, cover the slab with a layer of plastic. Wet curing will ensure an even and controlled cure. In cold weather, make sure that fresh concrete is protected from freezing.

About the Author
Gabe Martel
Gabe Martel is a project manager and construction superintendent in Pembroke, Ont., Canada, with over 35 years of experience
 

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Humidifying Homes
By Doug Horgan
DOWNLOAD THE PDF VERSION OF THIS ARTICLE. (1.47 MB)
Why would you want to add moisture to a house? As anyone who’s dealt with an expensive and challenging mold issue knows, moisture is often the problem in houses. Why would we deliberately add more? There are three answers I know of:

Low humidity causes wood to shrink (when it dries out); this can cause aesthetic issues or even cause things to break.
People are less comfortable when humidity is very low. Static shocks, dry nasal passages, and itchy skin are common issues.
There is some evidence that low humidity allows some illnesses to transmit more effectively, so higher humidity may reduce the likelihood of these spreading—but there are important reasons to be cautious with this information.
What Is the Right Level of Winter Humidity?
To prevent wood from moving around too much, we want to keep humidity somewhat even, so the correct level in winter varies with climate. Where I work, the Washington, D.C., area, it’s common for indoor humidity to run well above 50% for the humid half of the year. (I’ll be using relative humidity (RH) at indoor temperatures in this article.) Wood will condition to this level of humidity and measure around 9% to 11% EMC (equilibrium moisture content) during the humid months.


In winter, we want to limit how much the wood shrinks from its summer level, so the closer we stay to 50% RH, the less movement. Having said that, 50% is too high for normal buildings to handle in many climates, and in my experience, problems develop only when humidity runs close to 20%, drying wood to about 4% EMC. If we can keep humidity between 30% and 40%, EMC will drop only to 6% or 7%, and wood shrinkage will be acceptable. After all, it’s normal for hardwoods to have small gaps in winter; we just don’t want them to be so wide they are objectionable. We find even wider baseboards and crown moldings won’t shrink enough to break caulk lines as long as humidity stays above 30% most of the time.

If your summers are drier (typical of northern locations), you may not need to keep winter humidity levels as high as 30% to keep wood in good shape, whereas if your summers are wetter, your buildings may need to be humidified to more than 30% to prevent problems with wood. In other parts of the country, there may not be a significant difference in humidity between summer and winter, so it may not make sense to have a humidifier—at least for limiting seasonal wood movement.

Engineered flooring seems to have the biggest problem with large seasonal humidity swings. We’ve seen several floors, from multiple manufacturers, rip apart at glue joints between layers in homes with low winter humidity (around 20%—so far, no issues at 30% or higher). A look at the warranties may be disheartening; some “require” that humidity be kept in small ranges like 35% to 45% RH year round, which is possible only in tight houses with closed windows, humidifiers, dehumidifiers, and perfect operation and maintenance.

For more information on wood movement and EMC (equilibrium moisture content), see JLC article, “Managing Wood Movement”.

Cartridge steam humidifiers emit steam into HVAC ductwork when called for by the humidistat.
Cartridge steam humidifiers emit steam into HVAC ductwork when called for by the humidistat.
In the author’s climate, his company recommends clients set controls at 35% RH or lower (shown here marked up with colored pens), based on its experience that most buildings can handle 40% to 45% relative humidity in winter without moisture problems, and allowing for some inaccuracy or drift in the sensor.
In the author’s climate, his company recommends clients set controls at 35% RH or lower (shown here marked up with colored pens), based on its experience that most buildings can handle 40% to 45% relative humidity in winter without moisture problems, and allowing for some inaccuracy or drift in the sensor.
Striving for 30%. For human comfort, I have heard few complaints once humidity is maintained in the 30% range—despite what you may read. We work on many leaky houses and buildings where humidity can’t be kept much above the low 30s, or even high 20s in some cases. These houses don’t have super-dry static electricity issues or even many complaints about dry noses or skin; those start when houses run in the low 20s or lower for a few weeks.

In fact, John Straube, a principal at RDH Building Science, recently spoke of a client with itchy eye complaints on an ASHRAE Journal podcast with Joe Lstiburek. A doctor recommended a humidifier, but the symptoms became worse once it was in use, because the irritation was caused by mold growing in the walls, and the humidifier made the mold problem worse. This brings us to the wisdom of the internet.

If you search online for the “correct” level of humidity, you’ll come across a diagram that seems to state that optimal relative humidity is between 40% and 60%. The main evidence about keeping humidity this high comes from hospital wards where influenza has been shown to spread much more effectively below 40% RH.

I would never minimize this important data point, which has been shown in multiple studies. But, it’s crucially important not to overhumidify buildings in cold climates. Many houses in my area (climate zone 4) should not be operated at humidity levels above 40% or 45% in winter, or they will suffer from moisture damage, including growth of mold, bacteria, and other water-loving organisms (which themselves cause human health problems), wood rot and damage in walls and roofs, and also undesirable window condensation that can drip down walls, damage floors, and wet window shades. In colder climates than ours, the building envelope is that much colder, and condensation and moisture accumulation can happen at even lower humidity levels.

It’s easy to overhumidify ordinary buildings in cold climates. Standard windows, doors, and even walls and roofs are prone to condensation problems when indoor humidity levels are high. If you want to run a house at higher humidity, you have to build differently: more insulation, better windows, minimal air leaks, and thermal bridge protection—pretty much the recipe for a passive house—or use materials that can handle high levels of moisture and freeze-thaw conditions—the old recipe for hospitals and museums.

The respiratory pandemic we’re in has increased this kind of talk, but it’s not clear that higher humidity is helpful against SARS CoV-2. In fact, the one study I know of that tangentially addresses it indicated lower humidity may be helpful.

Whatever data or study one is looking at, high levels of humidity will definitely cause problems and must be avoided.

Portable vs. Whole-House Humidifiers
Many people use portable or plug-in humidifiers, which they refill regularly. Some scientists are concerned about using tap water in one type of portables, “ultrasonic” humidifiers, because the minerals and other junk in the water are turned into indoor air pollution. Other than that, and the inconvenience of managing them every day (including moving them to where people are), these can work.

Most of our clients install whole-house or automatic humidifiers so they don’t have to spend as much time and energy managing them. It helps that most houses in our area have ductwork for air conditioning and heating, which makes it easy to install automatic equipment. There are several different types of automatic humidifiers, but we use only two: flow-through pad humidifiers, and steam cartridge humidifiers.

Flow-through pad humidifiers use a disposable pad about a foot square by 2 inches thick. Water is piped to the top of the pad and trickles down, while air is blown through the pad. The large surface area encourages evaporation. In the off cycle, the pad dries quickly so mold doesn’t seem to grow on it, and some pads are treated with coatings that resist biological growth. These humidifiers are reasonably effective and are not expensive to install or maintain. They do use a lot of water, depending on how they are set. Much of the water doesn’t evaporate and instead heads down the drain. When you’re paying a lot for water and sewer, this adds up. Not to mention that many of these devices recommend using hot water, which obviously increases energy use.

We’ve seen a lot of pad humidifiers leak a bit of water, especially on startup in the fall. For this reason, we usually recommend them only for areas that can handle some splashing. Adding a pad humidifier to an upstairs system is risky, even when we’re able to install the oversized drain pan we insist on for new installations. (When possible, we run HVAC closet drain pans from frame to frame, before drywall, so even splashing or spraying can land in the pan.)

Flow-through pad humidifiers use disposable pads. Water trickles down from the top while air is blown through the pad. Pads are often treated to resist biological growth.
Flow-through pad humidifiers use disposable pads. Water trickles down from the top while air is blown through the pad. Pads are often treated to resist biological growth.
Steam cartridges. The second type of humidifier we use is a steam cartridge unit. This heats water in a replaceable plastic cartridge and pipes the resulting steam into an emitter in the ductwork.

Steam humidifiers are powerful and can put out terrific amounts of moisture—so much that we have to be careful with them. We’ve learned to install at least one safety device when we use these, either an “airflow proving switch” that won’t let the humidifier run if the HVAC fan is off, or a humidity safety switch that turns it off if levels inside the ductwork get too high. One of our HVAC subs installs both devices in case one fails. A problem with a steam humidifier is a big problem! I’ve seen two failures; both were discovered when water poured out of seams in the ductwork and soaked through ceilings and walls. The cleanups were big projects. Other issues I’ve seen with these are melted PVC drain pipes (follow installation instructions—usually the first few feet of drain should be metal) and a strange situation where all the steam went down one branch duct, overhumidifying one part of the house while leaving the rest of the house dry. (Moving the emitter solved that issue.)

If your building doesn’t have ductwork, there are options. We’ve installed a few steam humidifiers with a special wall emitter box that has a fan to mix air with the steam to help blow it around the home. I also recently saw a pad-type unit with its own built-in fan for a free-standing installation.

Steam humidifier cartridges do accumulate minerals and debris from the water supply, but they are easily replaced—typically annually. They are designed to fully drain in the off cycle.
Steam humidifier cartridges do accumulate minerals and debris from the water supply, but they are easily replaced—typically annually. They are designed to fully drain in the off cycle.
Reservoir humidifiers. Taking a cue from my indoor air quality friends, we no longer install reservoir humidifiers—whole-house units that fill a bucket with water and energize a heating element in the water. Because organisms grow in the water easily, this type of humidifier is a maintenance headache, requiring multiple thorough cleanings per heating season. An even worse version runs a wicking device (like a belt or disks) through the reservoir so water evaporates off the wick. These gunk up even quicker.

Reservoir humidifiers can be high maintenance and may present an indoor air quality risk; typical designs stay wet all winter, allowing the potential for organisms to grow in them.
Reservoir humidifiers can be high maintenance and may present an indoor air quality risk; typical designs stay wet all winter, allowing the potential for organisms to grow in them.
Cost comparison. Steam humidifiers are significantly more expensive than pad humidifiers. Installed cost is usually closer to $3,000, and annual replacement cartridges cost around $100, while the pad style usually installs for around $1,000, and replacement pads (also annual) are only around $20. Steam humidifiers use a small amount of cold water, which costs a lot less than the nearly constant stream of hot water that pad humidifiers use, so some of the cost is offset that way, but steam humidifiers also use a fair amount of electricity. Also, most steam units need a 240‑volt dedicated circuit, while the pad units can be added to existing furnace electrical circuits.

In short, in our area we recommend flow-through pad or cartridge steam humidifiers, and we warn people not to set humidistats higher than 35% to 40% RH based on the typical buildings and typical winter around here. In colder climates, this should usually be lower, but with better construction, it can be higher.

Wall emitter boxes are used with steam cartridge units where ductwork is not available to distribute the humidity.
Wall emitter boxes are used with steam cartridge units where ductwork is not available to distribute the humidity.
Humid supply air is hosed from a steam cartridge unit, typically housed in a nearby mechanical room or closet (left), to the emitter box, which has a built-in fan to mix air with the steam. Grills can be a bit obtrusive unless hidden in a hallway or other less visible location (right, top and bottom).
Humid supply air is hosed from a steam cartridge unit, typically housed in a nearby mechanical room or closet (left), to the emitter box, which has a built-in fan to mix air with the steam. Grills can be a bit obtrusive unless hidden in a hallway or other less visible location (right, top and bottom).
Pad humidifiers often drip or splash a bit of water, as on this galvanized metal pan, which has seen enough water to start rusting.
Pad humidifiers often drip or splash a bit of water, as on this galvanized metal pan, which has seen enough water to start rusting.
Steam humidifiers put out a tremendous amount of moisture, and if the HVAC fan doesn’t circulate it throughout the house, it will turn into water in the ductwork and leak …
Steam humidifiers put out a tremendous amount of moisture, and if the HVAC fan doesn’t circulate it throughout the house, it will turn into water in the ductwork and leak …
… as seen in the two photos above. The author’s company now uses a secondary safety device to ensure the fan is operating before the humidifier will run.
… as seen in the two photos above. The author’s company now uses a secondary safety device to ensure the fan is operating before the humidifier will run.
Photos by Doug Horgan; illustrations by Tim Healey

About the Author
Doug Horgan
Doug Horgan is vice president of best practices at BOWA, a design/build remodeling company in McLean and Middleburg Va.
 

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Prepping the Base
If the subgrade settles after you've poured the slab, you increase the likelihood of a crack. It seems obvious, but this is the cause of far too many problems. Several things can contribute to subgrade settlement, but the two prime offenders are soils with different bearing capacity across the area of the slab and improper compaction of the subgrade.

I have seen this over and over in my area. One day a bulldozer, next day forming up, third day pour. Weather be damned. They built a Family Dollar in record time, went in the first day, big cracks in the floor.
 

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One problem we have in the North is that since we use foam board insulation under the slab, the foam board slowly conforms to grade irregularities after screeding but before curing, resulting in dips.
 

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my company poured hundreds of thousands sq/ft of slabs ....i know more about concrete than i could ever hope to remember or share....concrete shrinks and expands so it will crack always......the only way to deal with it is to try to control where it cracks.....concrete slabs will even curl at saw joints.......concrete issues are manageable but you are dealing with temperatures, wind, humidity, sunlight, god made aggregates that are not perfectly uniform, aggregates that come from different parts of a pile, concrete that spends more time than others loads in a truck, some agitated more than others, concrete gains air in the mix, can lose or gain moisture in the truck, rebar/mesh/additives all can vary in temp etc, all these variables can apply to the subbase being poured on, each pour has its own characteristic's but they all crack, again the above is just the major variables there are a hundred more smaller variables