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DaveBell
Moderator
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# Posted: 30 Oct 2015 04:21pm
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Looking for opinions and advice on building a Concrete Slab vs using Piers. The site is on a mountain at 1800 feet and experiences mild summers and down to zero in winter. There is a road, I can get a concrete truck to the site.
I like the concrete slab because once it's poured with plumbing rough in and threaded J-hooks around the perimeter, it's done. Is there a standard spacing of the J-Hooks?
I don't know about cold floors in concrete slab vs piers. I know I can insulate the floors with the pier method. I'm also concerned with pipes freezing between the pier floor and the ground.
Thanks,
Dave
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MtnDon
Member
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# Posted: 30 Oct 2015 05:15pm
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You can have a warm concrete floor. Rigid foam is placed on the base and the concrete placed on top. R5 to R10 in most places. makes a big difference. Our home is on a slab, built with only R4 around the perimeter. One room I added has R5 under the entire slab. World of difference.
Our pipes were under the slab until we replumbed (old stuff was PB). It was buried below frost depth and run straight up through the slab. You could take a page from the re-plumbing book... just have the main supply buried and come up through the slab. Insulate around that if you want. Then run all the hot and cold lines through walls or ceiling. Use PEX. I have seen new homes around here (on slabs) run all the plumbing and heating/cooling air ducts through a chase in the ceiling. The pipes and ducts end up on the heated side of the insulation.
I should have asked if this is full time or part time recreational use.
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toyota_mdt_tech
Member
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# Posted: 30 Oct 2015 07:21pm
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I'd do what Mt Don sad, in fact, dont pour cement around the supply line coming through the slab, put it in a sleeve or tube made form larger plastic pipe. So if there ever was an issue, you can slide a new pipe in from underneath.
As long as you can get a full cement truck in there, could you do a full footing/stemwall?
Dave, J bolts, I'd go every 4 feet, but no more than 6 feet max and no more than 1 foot from each corner or an end such as a door opening. If you dont use one long board for the sill plate (treated) you must have a bolt no more than a foot in on each end of a splice, so try to get lumber that is long enough to go the full run without a splice. If you dimensions are longer that whats available, just have a spot where 2 bolts are 2 feet apart and put the splice right in between them. The bolts need to go in a min of about 7 inches on reinforced concrete, and 15 inches min on non reinforced concrete. They are 1/2" diameter, you want them 1-3/4" from the outer edge.
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rockies
Member
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# Posted: 30 Oct 2015 07:34pm - Edited by: rockies
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These articles should help.
http://www.greenbuildingadvisor.com/blogs/dept/musings/polyethylene-under-concrete-sl abs
http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/what-s-best-basement-floo ring-system
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adakseabee
Member
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# Posted: 30 Oct 2015 08:56pm
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HUD.gov has an excellent design guide in PDF format for Frost-Protected Shallow Foundations (FPSF). It covers both heated and unheated buildings. Illustrations are very clear.
http://www.huduser.gov/Publications/PDF/FPSFguide.pdf
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creeky
Member
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# Posted: 31 Oct 2015 10:48am
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that's a great article on fpsf. hadn't read it in awhile. good refresher.
in cold climates corners actually see double the heat loss due to the increased surface area. hence, the funny wings.
for those using their buildings seasonally an unheated fpsf is still a good solution.
I wanted to do an fpsf. but my soil is pure clay starting about 24" down. So i like helical piles.
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