be pouring the slab in a few weeks. have footer dug. Will install rebar next week. Have it inspected and then run plumin and electrical conduit. I've read plenty and some are saying sand and others rock. Back home it was always sand. Down here see lots of rock, but that's usually commercial. Haven't seen many residentials.
anyways, what's your flavor and why come?
Thanks
Rock here. Better drainage for any water. Patios and walks are typically sand or rock dust over 4" of rock. Probably a lot of that is driven by local conditions and site orientation.
Definitely driven by local conditions, but I like 21A recycled crushed concrete. I get it locally for $18/ton.
(https://forestryforum.com/gallery/albums/userpics/62288/PXL_20210126_193710345.jpg?easyrotate_cache=1621276204)
(https://forestryforum.com/gallery/albums/userpics/62288/PXL_20210128_224511489_MP.jpg?easyrotate_cache=1621276208)
Not a pro but have prepped for a few slabs and done quite a bit of research. From what I've read large crushed stone is the ideal since it acts as a capillary break and doesn't hold water.
That being said what I normally see around here is sand. I'm sure it's cheaper and easier to work with/smooth out. Gravel is popular too.
I often compromise and use 1 1/2" crushed rock with fines, which isn't a whole lot courser than most of the gravel we have around here. The only washed crushed rock easily available here is 2"+ and it's a bear to shovel and rake.
I'm sure site location is important. In some locations you can probably get away with murder and in others better mind your P's and Q's.
Alan
Architect here. We always specify stone/gravel and I've only ever seen stone/gravel specified around here by other building professionals as well. As others have said, drainage is the primary reason. A dry slab that doesn't wick moisture from below and stone doesn't hold moisture to frost heave when frozen although the soils below still can. I also believe stone compacts better as well so less chance of settling/cracks.
Quote from: alan gage on May 17, 2021, 03:12:27 PM
I often compromise and use 1 1/2" crushed rock with fines, which isn't a whole lot courser than most of the gravel we have around here.
That's what I primarily like about the 21A crushed concrete. Lots of fines that pack against the rock while still allowing for drainage. Also for compaction to minimize voids under slab. More than enough for patios and walkways in my opinion.
@Sedgehammer (https://forestryforum.com/board/index.php?action=profile;u=43840) if this is a slab that's going to see heavy equipment, I'd go with something similar to 21A with fines but compact with a plate compactor in 2 inch increments.
I used 1 1/2 is rock and fines then walked the dog ( compacted) for 3 days. I also watered it in at night.
This was on red clay
We have an ag base which is recycled cement with dirt added so it compacts. Looks similar to what @VB-Milling (https://forestryforum.com/board/index.php?action=profile;u=52288) uses
The fines are where the capillary, rising damp, action happens.
We only used gravel due to drainage issues, the valley floor is a hard pan clay prehistoric river bed so won't absorb moisture. It's like dealing with concrete in summer. A neighbour used sand under a decorative driveway/parking pad last year and it is already cracking from frost heaves.
I know it's not what you asked but I'd highly recommend insulation under the slab. Even if you don't think you need it in Oklahoma weather I think you'd notice a big difference with interior humidity levels. The concrete slab will be cold since it's in direct contact with the soil underneath which causes it to condense with hot and humid air above. It still gets hot and humid in my shops when it's hot and humid outside but the floor never sweats (like most other buildings I've been in) and I can easily keep the humidity down with a regular home style dehumidifier (1200sq ft shop).
My dad's insulated shop on the other hand (non-insulated slab) is very clammy during humid weather with sweaty floors.
And to bring it back to the original question the foam makes a really nice capillary break. :)
Alan
Washed, crushed granite here. If base needs to be built up, we use the same thing as railroad ballast. For the top layer, I use fine washed crushed granite. They go by a number each here, but I understand the numbers aren't the same all over.
I use the 88 stone (fine) as the top layer because it's so easy to grade out level. The railroad ballast locks together, so it's hard to grade it out smooth enough, if you're doing it by hand. The 88 stone grades easier than dirt, to a line pulled across the top, and the distance judged to the line by the grading tool you're using, like a hard toothed rake upside down, or a concrete come-along without the wire hook.
We have an endless supply of granite here though, and the nearest rock quarry is only 15 miles from us.
Quote from: alan gage on May 17, 2021, 05:54:16 PM
I know it's not what you asked but I'd highly recommend insulation under the slab. Even if you don't think you need it in Oklahoma weather I think you'd notice a big difference with interior humidity levels. The concrete slab will be cold since it's in direct contact with the soil underneath which causes it to condense with hot and humid air above. It still gets hot and humid in my shops when it's hot and humid outside but the floor never sweats (like most other buildings I've been in) and I can easily keep the humidity down with a regular home style dehumidifier (1200sq ft shop).
My dad's insulated shop on the other hand (non-insulated slab) is very clammy during humid weather with sweaty floors.
And to bring it back to the original question the foam makes a really nice capillary break. :)
Alan
Original plan was to install infloor heat. Boss nixed that, as she wants to save more for the house. Plan is to be in here only a couple of years. We'll see on that........ I know plastic stops the concrete from being wet in the summer, plus we'll be cooling this. Haven't read up on using it in a non heated floor. I'll read up on that.
Thanks
Under neath the the floor is packed millings. It's the area where we parked our dump trucks. This is the highest point in the drainage vacinity, there's really no possibility of water.
We'll be lifting the pad 5" where the area for parking veichles us. 8" where the kitchen/dining/bathroom is. Underneath the compacted millings is red clay.
I use compacted gravel, and then the last inch or two with sand so I can screed it off. I always use poly sheeting for a vapor barrier, and I would second the insulation as well. In our basement, I have an area that I left the under slab insulation out because of a load bearing post that beared on that spot, and it always gets condensation on it. You can see the square that I left the insulation out. Compaction is important, a plate compactor and 3-4" lifts are your friend.
wet sand is a conductor, dry sand is an insulator. put down plastic, then sand, then put pex every foot on the 6x6 wire mat and pull it to the center of the slab. even if you do not hook it up, in 30 years it will be a selling point for someone if you sell your place. the pex cost me about 300 bucks back in the day for my 4500 sq. ft. shop.
ive been doin concrete for over 30 yrs and we only use 21aa crushed concrete, unless otherwise specified,, sand sucks ,,,
Quote from: doc henderson on May 17, 2021, 09:16:16 PM
wet sand is a conductor, dry sand is an insulator. put down plastic, then sand, then put pex every foot on the 6x6 wire mat and pull it to the center of the slab. even if you do not hook it up, in 30 years it will be a selling point for someone if you sell your place. the pex cost me about 300 bucks back in the day for my 4500 sq. ft. shop.
I'd need 2" of pink then. Lord only knows what that costs now. I had heard that one of the plants when down in that freeze in TX and it solidified, as they ran out of heat, so shortage on that also. I understand on the resale. I tried to convince her even to put it in, as the heat is so, so much better.
Doc, what size pex you run? Thanks
Just checked maynards. 2" is $53. 2.5" is $35........ Now that makes a lot of sense. I suppose the demand is in the 2" and not so much with the 2.5".
Quote from: barbender on May 17, 2021, 08:44:53 PM
I use compacted gravel, and then the last inch or two with sand so I can screed it off. I always use poly sheeting for a vapor barrier, and I would second the insulation as well. In our basement, I have an area that I left the under slab insulation out because of a load bearing post that beared on that spot, and it always gets condensation on it. You can see the square that I left the insulation out. Compaction is important, a plate compactor and 3-4" lifts are your friend.
In that spot you left out the poly also or that's with the poly, but no insulation?
i havent poured yet, but i did my little shop base in coarse rock (3-5" limestone)compacted on top flat, bare clay and then capped that in compacted "crusher run" (3/4" down to dust) because the topography, property lines and runoff constrained things and made proper drainage worrisome.
anyways water can flow in one side and out the other quite impressively without the surface gravels getting wet. my logic is that having the porosity and voids in the base rock to leave room for water expansion would prevent frost heaving if the runoff path away is somehow compromised and water migrates towards it. also if the water can run through so can the air, and that will help dry the slab sub base much faster.
we have a lot of humidity and fungal activity that i dont want migrating into the wood.
this is the same base ive been laying down for driveway and the big forktruck can drive over it loaded without rutting it at all, so i guess thats my seal of approval. that machine will squish water up out of the desert.
Quote from: Sedgehammer on May 18, 2021, 07:23:36 AM
Quote from: barbender on May 17, 2021, 08:44:53 PM
I use compacted gravel, and then the last inch or two with sand so I can screed it off. I always use poly sheeting for a vapor barrier, and I would second the insulation as well. In our basement, I have an area that I left the under slab insulation out because of a load bearing post that beared on that spot, and it always gets condensation on it. You can see the square that I left the insulation out. Compaction is important, a plate compactor and 3-4" lifts are your friend.
In that spot you left out the poly also or that's with the poly, but no insulation?
The standard colored foams are XPS. You can also use white foam (EPS) under slabs as long as it's dense enough. I used to have to order it in special from a local company that makes energy panel buildings but now our local lumberyard is carrying it in 2". It's a little cheaper and supposedly more environmentally friendly to manufacture. It doesn't crumble like the cheap version of white foam most of us are used to.
Both sides (XPS and EPS) make the case that their type of foam is best for use under a slab. XPS says it doesn't absorb as much water. EPS says that while it might absorb more water it's also able to quickly release the water, which XPS isn't.
I don't have enough experience to say how much difference there is between poly and foam when it comes to floor condensation. But I do know that a pepsi can is vapor impermeable but it still sweats on a hot day if the contents are cold.
Alan
Poly won't do anything for condensation, it's only a vapor barrier. Here's a case in point- a local farm and fleet bought a building that was built as a Wal-mart. They wanted to do decorative epoxy coating on the floor, but the contractor in charge of the project advised against it because they were aware the slab had no vapor barrier under it. The company pushed for it anyways, and now that floor looks like trash. Peeling up and flaking off everywhere. What happens is vapor gets through the slab (concrete is vapor permeable) and is trapped under the epoxy coating. When they run pallet trucks over it, the epoxy basically pops and then starts to flake off.
Sedge, my floor has poly throughout, even the area where I left out the insulation.
@alan gage (https://forestryforum.com/board/index.php?action=profile;u=36602) @barbender (https://forestryforum.com/board/index.php?action=profile;u=1286)
Been all over the interwebs trying to find some affordable 3" EPS..... :o
if 2" then the XPS. It looks though like the EPS is a wee bit cheaper per R, but I know she'll really not be happy on the added costs.....
Trying to figure out a way to hide the purchase..... :D
House basement is drainage stone with plastic on top before pour. Garage floor is gravel 2" higher at the back, sloped toward overhead door, with plastic on top before pour.
Quote from: Sedgehammer on May 18, 2021, 12:12:41 PM
@alan gage (https://forestryforum.com/board/index.php?action=profile;u=36602) @barbender (https://forestryforum.com/board/index.php?action=profile;u=1286)
Been all over the interwebs trying to find some affordable 3" EPS..... :o
if 2" then the XPS. It looks though like the EPS is a wee bit cheaper per R, but I know she'll really not be happy on the added costs.....
Trying to figure out a way to hide the purchase..... :D
When I was ordering EPS foam from the energy panel place I was getting 4" for the same cost as 2" XPS at our local lumber yard. And I could get it in 10' sheets which helped with layout. It was always a bit of a hassle ordering from them though as it wasn't something they normally did and I was very small potatoes.
Now that our local yard carries the 2" EPS it's much easier to just get it there but cost is higher.
When you're searching for EPS foam you need Type IX to get to the same 25psi compression as standard XPS.
You better tell your wife to get used to the added costs because there's going to be a lot of them. :)
Alan
Do the math, you may or may not need high density foam, for a residential garage no, serious commercial loads I'd probably skip the foam. You're likely on something around 2000 psf soil from the description. There are 144 square inches in a square foot= ~14 psi. Is there something on the slab that is going to be putting down that kind of load. For us wet EPS= happy ant colony.
I think you are getting very good advise on this forum. Spending other people's money is a national pastime and building professionals are great at it and this also applies to your rebar thread
A big part of an engineered foundation is based on soils and barring a full soils report which is rare and overkill for most residential construction, I would tend to rely on the advise of your local reputable concrete contractor. Why? Because they have pored more foundations in your area on your soils and seen what works (and doesn't) more than anyone.
What we spec for clients is one thing but what I will say is how I built my own shop with my own money and sweat equity, in my area.
No way I'm using fiberglass rebar. Why? Not much history to base performance on. It may be way better but metal works and I don't want to experiment on my own building.
Full depth (4' deep here including footings) frost walls on 12"x24" footings. 3 rows of 1/2 rebar on 3" chairs. I agree with Rodman on the other post that corners aren't really necessary but I own a rebar bender so I spent a few hours doing them myself with 10' rebar, 5' of overlap per leg, tied in 3 places.
Important IMHO, All gravel for backfill around the frost walls under the slab. Save the dirt for somewhere else. You'll never compact it well enough to avoid settling. Fines makes compaction better but drainage worse so it is a trade off. Because we have frost walls and under slab insulation, we do have some fines in our gravel but I would avoid fines on an uninsulated slab on grade.
I used 2" XPS and agree that while expensive, it is worth it and your wife will/would agree first time her socks get wet on a spring day. We also installed PEX (pex A, oxygen barrier) which isn't cheap but we are adding radiant heat. I agree with others that regular PEX B is cheap enough to Keep your future options open.
Control JOINTS. Lay out where you can live with some saw cuts and try and get them 1/4 as deep as your slab is (without hitting your Pex). Under partitions is a good place and try and get them in every 20-30' square. Concrete always cracks but if they crack in your control joints, nobody ever knows but you.
Quote from: Don P on May 18, 2021, 04:44:57 PM
Do the math, you may or may not need high density foam, for a residential garage no, serious commercial loads I'd probably skip the foam. You're likely on something around 2000 psf soil from the description. There are 144 square inches in a square foot= ~14 psi. Is there something on the slab that is going to be putting down that kind of load. For us wet EPS= happy ant colony.
Don...... if wet EPS = happy any colony, then ain't you tellin me to use high density foam..... ??? :o ??? :D
1/2 inch. I think. I will try to find pics of the layout. oxygen barrier. runs about every foot apart. every 6 inches along the walls and windows. for 3 lines. the upstairs of the shop is 34 x 50 and i divided that into 6 sections of equal total length, so the resistance in each line into the manifold is about the same. so the sections further away are smaller so the overall length is the same in all 6 lines. I put down plastic then sand, and after the sand dries out it insulates well. and I have picture and wood in the basement of the shop, and it is dry as a bone. I use the concrete expansion joint as a thermal break along the walls and use dimple board folded at the edge for a French drain into the drain tile around the basement. the only insulation under the slab, is the dry sand over the poly, after everything cured and dried out.
Nope, standard weight xps 15psf if available is a little cheaper. Nothing wrong with 25 but I see it sometimes promoted as "gotta have the high density under a slab", not so for most uses. Sorta like gotta have oxygen barrier pex.
Pex spacing of about 12" or less is good, we ended up at about 9" but what is more important is keeping your loops at about 200' or so and relatively equal lengths. I made sure my shorter runs were at the perimeter and oriented them with supply side outward (warmer water) and return side (cooler) towards the middle of the slab. I used 1/2" PEX and that is one of my regrets for non obvious reasons...
1,000 ft of 1/2" pex hold 9 gallons of
water/glycol. 1,000 ft of 3/4" pex holds 18 gallons. We are installing a propane fired low-mass combi-boiler for DHW and heat and after running all the heat loss calcs, the extra mass of water would have lengthened our boiler run times enough to substantially reduce the risk of short-cycling during non-peak loads. As it stands, we are borderline for the smallest combi-boiler we can get and the larger pex would have been a lot cheaper than installing a buffer tank if we end up needing one.
A btu is the amount of energy required to heat 1 lb of water 1 degree F so that extra 9 gallons of water weighs about 75 lbs so 750 btus to raise that water temp the 10 degrees of a typical boiler cycle. That extra 75 lbs of water buys you an extra 5 min of run time on a low firing 10k btu/hr boiler which makes a big difference in the number of cycles per hour at a given heat load.
@Don P (https://forestryforum.com/board/index.php?action=profile;u=17) I got yeah. I agree. Came to that conclusion also, but missed the reference to the 15 psi vs the 25 psi on the high density
You mentioned not really needing oxygen barrier pex. Why is that?
@doc henderson (https://forestryforum.com/board/index.php?action=profile;u=41041) No insulation under the slab goes against everything and i mean everything I've ever read. I do get the thermal moisture break by placing the plastic under the sand though. Was that your idea or did you pick that up some where?
@nybhh (https://forestryforum.com/board/index.php?action=profile;u=38169) In my old house in wiscony we did 6" along the outside walls and then 12" there after. max of 300 ft runs. If there is a heaven, it's having warm floors. It worked great. What i did on my manifold was to install manual shut off valves on each loop. in the basement manifold we had 6 zones, ground floor, 6 zones and the upstairs we had 4 and one thermostat on each floor. I gradually opened and closed each valve until I reached the desired temps in each room. Took a few weeks, but once done, never changed it
Interesting thoughts on the 3/4 inch. shorter cycles are of a concern here also due to the not so cold days in the winter at times. we're zone 7, so winters aren't typically bitter cold
Thermal breaks against exterior wall is a bit harder. This is a slab poured on top of the footings. we dug the footings and will pout them to ground level. Then we'll place forms on top of the footing and the slab becomes the start of exterior wall
QuoteYou mentioned not really needing oxygen barrier pex. Why is that?
Same thing, nothing wrong with it but there is an air trap and very little oxygen transfer through normal PEX. IMO more salesmanship.
I did the same as you and read and spoke to a lot of folks. Some told you how to do it based on what they were told and a few seem to understand the concepts and gave info like a PhD Professor. The basement slab is in a sloped area so one end is under grade, and the other is half under and has egress windows. It is a shop basement but it could easily be converted to a living area. It is so warm and dry that I would put carpet down there. I am surrounded by folks with wet basements. there is even a pond in the high rent area a block to the north, just for all the sump pumps to go into when they were building the new homes. My slab is insulated. with dry sand. The shop is 4500 sq. ft. with the basement, garage and shop area above the basement. It costs less to heat than the house that is also 4500 sq. ft. The guy that gave me that idea also said I needed 1.5 inch foam under the floor of the shop upstairs or it would take forever to heat. that was a waste. I have the whole shop on one thermostat. I keep it 55° and use the wood stove in the dead of winter to heat my little piece of heaven when I am working in the shop. floor heat as you know takes some time to heat up and cool down due to thermal mass. the floor over the basement, is plywood with the pex fastened, and then a 1.5 inch fiber reinforced slab screeded between sleepers. only one crack in a dog leg around the stairs going to the basement. I have no purpose in trying to convince you, but you are looking for ways to not spend on insulation. sand will be there anyway and it is cheap.
I was told with oxygen barrier you could use regular circ pumps. without you needed brass impellers and such. It was about the same price and was told it would keep the components from corroding as much. I agree, regular pex is prob. fine.
@Sedgehammer (https://forestryforum.com/board/index.php?action=profile;u=43840) For thermal breaks at the exterior... we poured our frost walls with a 4" curb on the outside that creates a shelf on the inside for the insulation and slab to "sit" on. Because our exterior walls are 2x6 (5.5") and align with the outside face of the curb, we were able to wrap 1.5" xps vertically up the inside face of the curb to create a thermal break for the exterior edge of slab and keep it hidden below the sill plate. You can cut the insulation at a 45 on the table saw as well so it comes to a point if you don't want to see a 1.5" blue strip along the perimeter of your slab until your walls go up (be careful at door thresholds though).
I trust my plumber (long working relationship) so I took his advise in the PEX A/Oxygen barrier debate. Reasons were all as above. I was purchasing all the materials directly so he had no financial incentive one way or another but he is very good, a pro really, at spending my money.
Good luck with it.
all of the wall that is below grade, has the dimple board on the outside. it is plastic and prevents wet soil from contacting the 8 inch basement walls. if water gets through it has a half inch air space and goes to the footing drain. I used it inside on top of the footing and folded 90° and 4 inches up the wall. I put expansion material 4 inches along the wall and used this to screed the floor in the basement. If a pipe broke, the water could go to the edge and roll down into the drain tile and to the sump. also worked as a thermal break at the edge of the slab. It is a french drain around the floor with drain tile under. hard to explain, but the build was in 2005 and those pics are on an old computer.
Quote from: nybhh on May 19, 2021, 07:41:00 AM
@Sedgehammer (https://forestryforum.com/board/index.php?action=profile;u=43840) For thermal breaks at the exterior... we poured our frost walls with a 4” curb on the outside that creates a shelf on the inside for the insulation and slab to “sit” on. Because our exterior walls are 2x6 (5.5”) and align with the outside face of the curb, we were able to wrap 1.5” xps vertically up the inside face of the curb to create a thermal break for the exterior edge of slab and keep it hidden below the sill plate. You can cut the insulation at a 45 on the table saw as well so it comes to a point if you don’t want to see a 1.5” blue strip along the perimeter of your slab until your walls go up (be careful at door thresholds though).
I trust my plumber (long working relationship) so I took his advise in the PEX A/Oxygen barrier debate. Reasons were all as above. I was purchasing all the materials directly so he had no financial incentive one way or another but he is very good, a pro really, at spending my money.
Good luck with it.
Thanks, need it and the good kind..... :D
Had thought of that on the pour. That requires twice the form material. With todays costs of lumber, I dunno. I have a bunch, have to go do a look see. I'd prolly pour a 8" or 9", since 2x6 framing plus width of siding and interior getting. Wood cut the blue on a 45° like you said.
Did you design the layout the pex yourself or did you have a layout plan to go by?
I did mine but with the general rules of not overlapping. closer along walls esp with windows. If you use the 6x6 mat it is easy. every 6 inches along the wall. my floor of 34 x 50 wound up being 6 sections of about 17 x 17. My boiler was in the basement and I put the equipment under the stairs. I divided in two down the long center of the floor with 3 sections on each side. so 3 line came out 6 inches apart and ran around the outside perimeter. then as the came back one line would end up doing each of the three sections and back into the basement. I used clips upstairs on the plywood, and wire tied in the basement. do not overlap or make a splice that is in the concrete. a neat pattern will help if you need to make a hole in the floor without hitting the pex. you can also spritz the floor or mop it and turn on the heat and see the evaporation pattern. the basement was the same plan. the garage area was 34 x 34 so 4 sections there.
@doc henderson (https://forestryforum.com/board/index.php?action=profile;u=41041) I laid it out 6" for 2 runs on exterior walls. Then 12". I think there some on 18" in the center of the concrete pad. That layout was provided by the outfit that I bought the material from. Wood be nice to have a layout
sounds about right.
took a bit from 2005 to find. here is a pic of the basement prep. sand over plastic. the trough in the middle is to pour a reinforced beam/footing to support a center wall down the middle.
(https://forestryforum.com/gallery/albums/userpics/51041/pex.jpg?easyrotate_cache=1621452371)
Here's a link to the Building Science website about sand over poly under a slab. They aren't so enthused about the idea and give their reasons why.
Concrete Floor Problems | Building Science Corporation (https://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems)
Obviously it's worked fine for Doc and I'm sure it's worked fine for a lot of other people too. What percentage of people have problems with it? I have no idea.
Not trying to knock Doc or his reasons for going that route. Just pointing out the other side of the argument. If I had to guess I'd guess all methods work most of the time and that it's the questionable sites or other oddities that require best practices, for lack of a better phrase.
I only have experience building a few structures for myself so all I really know is what I've done and how it's worked for me. I do know that when getting ready to build my house I about drove myself crazy reading how things were supposed to be done and seeing just about every local contractor seemingly doing it how it's not supposed to be done. Some things I decided if everyone else is doing it that way it should be good enough for me and other things I did differently, what I thought was better.
So far so good. Nothing has come back to bite me in the butt.
I figure that whatever the good local contractors are doing is good enough and try not to mess with it too much but sometimes I just can't help myself.
Alan
I did put sand over my plastic, for a couple of reasons. One, so it had some protection during the pour. And two, one of my buddies who had poured a lot more mud than me told me if I poured right over the poly to be ready for a late night, reason being with poly directly underneath all the moisture had to come out the top. Idk🤷🏽♂️ No problems, but that doesn't mean there couldn't be issues.
Here's a few pics of ours WIP...
(https://forestryforum.com/gallery/albums/userpics/48169/8C19E62F-7C36-4AF6-8B3A-D2463952A9BB.jpeg?easyrotate_cache=1621455758)
(https://forestryforum.com/gallery/albums/userpics/48169/379D461F-E466-4F7F-8C53-C74F8399ED88.jpeg?easyrotate_cache=1621455823)
Be sure to pressurize the system and make sure there are no leaks before or during the pour...
(https://forestryforum.com/gallery/albums/userpics/48169/A8A085A7-B6A5-4643-BEF2-CB7890081FD4.jpeg?easyrotate_cache=1621455756)
These are 2-year old pics at this point and still no cracks. We do have 1.5" deep control joints every 15' in our 6" slab so I'm sure there are cracks in those joints but nothing visible to the eye. Crete Contractor shot a laser 2" down from the slab surface before the pour to make sure no pex was in the danger zone and didn't seem 1/4 as nervous as me staring at that pressure guage when he saw cut the control joints.
Alan, that article you linked was very interesting, but the author struck me as over the top opinionated to the point I would have to research more to trust the info.
Quote from: barbender on May 19, 2021, 04:38:38 PM
Alan, that article you linked was very interesting, but the author struck me as over the top opinionated to the point I would have to research more to trust the info.
Yes, he can be quite opinionated. I think part of it is also his style of delivery. He's in a business that seems like it would be very dry and boring but he manages to keep the articles entertaining (and down to earth enough) to make them readable to the layman. Most of them don't come off as biased as that one. Some articles dive in depth with the comparing multiple ways to do something and others are more like the one I linked. It's an interesting place to look around.
When I stumbled on them a few years ago I read a lot of articles on their site and learned a lot. Read a lot of opinions elsewhere from people who both agreed and disagreed with them but overall he (and the rest of the team) seem to be well respected and know their stuff. Overall I found their articles very helpful with information I couldn't find elsewhere.
Alan
Joe is the real thing, after years of reading his stuff in trade mags he started that website. I've seen him come back later in articles to the trades and noisily say "what was I thinking, that doesn't work! :D". It goes a long way with me when someone will own and advertise their mistakes as a cautionary example to those around them. BTW the gauge will rise as the concrete heats up while curing.
I was told of problems with cracking of you poured over foam insulation. so i did it the way I did, and it worked well. all good info. my way was cheap so I included it.
I've heard of curling problems pouring directly on poly, which I've done plenty but am not about to say I'm a concrete pro.
@alan gage (https://forestryforum.com/board/index.php?action=profile;u=36602) What a great article! He certainly knows how to write in an entertaining way and is clearly comfortable "pushing buttons" lol and we all love a bit of sarcasm as long as it isn't directed at us! I think his delivery might turn some people off but the message is sound in my humble opinion.
Anything can work in some locations and nothing will work in others. The elusive goal of "rule of thumb" construction is to find the most affordable solution that will work well enough for most cases, in most locations, and can be executed my most contractors. Its a very difficult challenge.
To be as old as it is, concrete is certainly one of the more technical building materials out there but we ask a lot more out if it these days, both performatively and aesthetically than the Romans did.
A couple of beers into my evening, I have to say I've thoroughly enjoyed this thread!
If you are going to form a stem wall around the perimeter, just put your foam vertical inside the stem wall and cut it off just below the slab. I like to have a ledge for the slab to sit on, so used to nail 2- 2x4's around the inside of the form for a 8" wall, so you have a 3" ledge. And I like gravel under your slab, you never know what crazy thing will cause you to build up water under your slab, maybe a plumbing leak or some other crazy thing, and the rock will release that water. Sand does not allow the water to flow like gravel. I always used to put drain tile in basements, did that for my daughters house, and used gravel under the slab, ran the pipe outside the footings on the walk out side of the basement, showed my SIL where I left it, and told him to put a pipe in when he had his sewer system put in. He did not. Last year they built up water under the slab, and couldn't get rid of it till they dug in a pipe to drain it. Daughter got new carpet in basement. They didn't have trouble for about 13 years till we had a crazy wet spell, including a big flood. The flood didn't get in their house, but it soaked up everything.
I'd have to say I just thoroughly enjoyed Joe's article... guess that means I hadn't read it before posting my last comment ::) :D.
Doc's pic shows a thickened footing section to be poured monolithic with the slab, don't forget to thicken under load bearing elements. I got called in on a TF job run amuk one time. Went into the basement and a post was doing its best to punch through the slab, the numbnut had put a serious post load on a 4" thick slab. From the pile of concrete debris, that had been his second attempt at the basement :o.
Another Building Science article I just came across you might find useful, Sledgehammer. This time about slabs, stem walls, and how best to insulate them. It's a newer article and has links to past articles on the subject. Not so opinionated but still entertaining. This protection board also needs to deal with critters such as rodents. Don't underestimate the animal kingdom. I particularly hate mice.
BSI-118: Concrete Solutions | Building Science Corporation (https://www.buildingscience.com/documents/building-science-insights/bsi-118-concrete-solutions)
I've done slabs and stem walls on 3 structures (a house and two shops). Each one was done a little differently and each one found me laying awake many nights as I tried to think through every step and how best to construct it. Best being a combination of cost, ease of me doing the work, and actually working as planned long term. Articles like the one liked above really helped me visualize the different methods as well as pointing out pitfalls I wouldn't have figured out on my own. I was fortunate that 2 of the 3 buildings were on sites with a deep gravel base and very low water table. Also fortunate that we don't have termites to deal with.
On one of my shops I used exterior insulation on the stem wall and allowed the metal siding to extend below the framing to cover it. When the building was backfilled the metal siding was covered. I figured this would protect the insulation it but I did underestimate the animal kingdom, namely my chickens, who continually scratched away at the soil on the south side of the building as they would sun bathe and uncovered the insulation, which they promptly pecked clean off the wall.
Alan
im jumping in the middle here without reading everything so forgive me if its been mentioned. i have a friend who is an engineer at a boston based architecture company doing interstates and major urban buildings. it is safe to say he is a concrete pro and i get my advice from him via text pretty often. biggest thing he ever warns me about is to "haunch" a monolithic slab. as they dry, slabs want to curl up like a potato chip. if its a 4" center thickness.. make its a 6 or 7" crust around the perimeter. i rarely see this mentioned. and building science guy is the first place i go.. that dude doesnt sugar coat.
@doc henderson (https://forestryforum.com/board/index.php?action=profile;u=41041) Thanks Doc for going to all the trouble.
Here's what I am going to do
1. pour a 12" wide stem wall up to floor level. This wood have cut outs for a 1.5"x1.5" lip for siding and a 4.5" wide by 6" deep for the slab to sit on
2. plastic on grade run up sides of stem wall to level of the EPS that is going down
3. put down a 10 mil or so plastic on current grade
4. put down sand to EPS grade
5. put down type ll 2' EPS
6. lay down either 1/2" or 3/4" pex-al-pex. This has memory due to the aluminum core inside, so I can lay it down with few fasteners. if 3/4 I can have fewer runs, as runs can be longer
7. go crazy
(https://forestryforum.com/gallery/albums/userpics/53840/20210521_125124.jpg?easyrotate_cache=1621619477)
(https://forestryforum.com/gallery/albums/userpics/53840/20210521_121558.jpg?easyrotate_cache=1621618732)
looks great. any drain tile along the footings?
Quote from: doc henderson on May 21, 2021, 03:52:42 PM
looks great. any drain tile along the footings?
no need. this is the highest point in it's area. everything drains away