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RobThompson
Caution - Newbie Alert LinuxMint
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join:2012-02-14
Lasalle, QC
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·AcroVoice

Minimum thickness of concrete over sprayed foam floor

Hello:

The floor of my 30" to 50" high crawl space is exposed bedrock. The surrounding foundation walls are spray foamed to 3". The ceiling is the exposed joists and sub floor of my single story 30' x 40' house.

The crawl space is heated and part of the whole house (heat recovery) air exchanger system.

I want to spay a 2" thickness of foam over the bedrock floor (aka: 30' x 40' heat sink) as it is very uneven so I cannot use sheet EPS.

My question is what would be the minimum thickness of concrete to place over the spayed foam? I just needs to be thick enough to walk on (crawl on, really) when I need to play with the plumbing and/or electrical. (And maybe store stuff like the lawn mower etc).

Thanks for any input on this.
--
Rob.
Blog: »googlevoiceforcanadians.com/
"Mankind" is a misnomer.


RobThompson
Caution - Newbie Alert LinuxMint
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join:2012-02-14
Lasalle, QC
I spoke to a builder and he said just put down the spray foam and don't cover it - put plywood sheets down where I want storage.

He also recommended, where possible, to put crushed stone and poly under the foam.


Tursiops_G
Technoid
Premium,MVM
join:2002-02-06
Norwalk, CT
kudos:1
Unless you have an Electric mower, I wouldn't store it (or ANY Gasoline powered equipment, for that matter) where gas fumes could potentially enter the house...

-Tursiops_G.
--
If You're Unsure, "RTFM"... If You're SURE, "RTFM" Anyway.

robbin
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join:2000-09-21
Leander, TX
kudos:1
reply to RobThompson
I was thinking plywood also. However if you did a light weight framing for it before spraying the foam the bottom of the framing could be imbedded into the foam providing support and you now have a floor structure to install the plywood on after foaming.

I see no reason for poly if you use a closed cell foam. It does the same job only better. A layer of gravel would allow water to drain. Not sure if that would be needed or not.


Msradell
P.E.
Premium
join:2008-12-25
Louisville, KY
reply to RobThompson
I was thinking the same thing as Robbin about using closed cell foam and forgetting about the poly it will certainly make it a lot easier. Putting gravel under the foam sounds like a bad idea because with pressure from above it could shift and cause the foam membrane to break!

Depending on how rough the area is plywood may cause problems because of the unevenness of the finished surface. It certainly wouldn't be much easier however than putting in a concrete surface. If you decide to go with the concrete I would think that about 2 inches would be plenty. It's not as if it's going to be supporting a lot of weight. I wonder it would be worth checking around to see if he could get someone to blow the concrete. They use that technique all the time for swimming pools and it certainly would be a lot quicker than trying to carry in the concrete.
--
Written using Dragon NaturallySpeaking


RobThompson
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Lasalle, QC
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·AcroVoice

1 edit
reply to RobThompson
Thanks people.

A few pictures, before the house was built, here: »www.dropbox.com/sh/c7ws0xe8a0b06···R38--L7Y

and one after.

H_T_R_N
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join:2011-12-06
Valencia, PA
kudos:1
reply to RobThompson
Depending on the code in your area the foam might need be covered by a fire rated covering. Check first.


LazMan
Premium
join:2003-03-26
canada
said by H_T_R_N:

Depending on the code in your area the foam might need be covered by a fire rated covering. Check first.

Just what I was going to say...

Because it's conditioned space, it has to meet code; and that generally means foam must be covered with a suitable fire-resistive barrier; shot-crete, drywall, etc...


RobThompson
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Lasalle, QC
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·AcroVoice
Hello:

I was told that I did not need to cover the spray foamed walls because the headroom in the crawl space was less than 60".

I don't know what they will say once I foam the floor.
--
Rob.
Blog: »googlevoiceforcanadians.com/
"Mankind" is a misnomer.


Tex
Dave's not here
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Was this an afterthought? If not, why didn't you have this done before the crawlspace was enclosed, especially since you say this space is being heated? Also, what is this "whole house (heat recovery) air exchanger system" you mentioned? I'd be interested in more details.


RobThompson
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Hi Tex:
Not an afterthought, just took some bad advice.

Here is the unit that I have: »www.lifebreath.com/products/resi···/205-max

In Quebec, all new houses [must] have a whole-house ventilation system, the heat recovery part is optional.
--
Rob.
Blog: »googlevoiceforcanadians.com/
"Mankind" is a misnomer.

H_T_R_N
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Valencia, PA
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Reviews:
·voip.ms
reply to RobThompson
said by RobThompson:

Hello:

I was told that I did not need to cover the spray foamed walls because the headroom in the crawl space was less than 60".

I don't know what they will say once I foam the floor.

By whom? If the space shares that air with the rest of the house in any way shape or form, there is a good chance it will need to meet the same code as the rest of the house. If the contractor is saying that it doesn't, a quick call to the CEO will get you the correct answer in short order.

MaynardKrebs
Heave Steve, for the good of the country
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3 edits
reply to RobThompson
You're in Quebec.
The foam used must meet CCMC (Canadian Construction Materials Centre) approvals to be used.
No CCMC approved foam is permitted to be exposed within conditioned living spaces - it must be covered with an approved 30 minute fire rated barrier (1/2 drywall or an approved spray-on fire retardant coating, or concrete in the case of your floor..

Your 'crawl space' is conditioned space according to what you have said, ergo you must cover the walls and foamed floor.

2" of 30MPa concrete is certainly strong enough to cover over 2+Lb. closed cell foam (min. 2lb. foam please), but because your improved 'crawl space' might be considered 'basement' under code, you may be forced to install 4" of concrete (20MPa is fine in that case).

When spraying the foam, there at two ways to deal with the foam/concrete application:
1) spray 2" of foam over the bedrock - you'll have an uneven foam layer +/` several inches (or more) depending on how uneven the bedrock is, then pump concrete in to 2"+ above the highest foam point.

2) find the high point of the bedrock. Drill a hole there and stick in a peg that extends 2" above the bedrock. That's the height of foam which needs to be sprayed evenly across the whole crawl space. Then top with concrete.

Suggest you use Lafarge 'Agilia' (or some other self-levelling/self-consolidating concrete) via a pumper.

Method 1 is less expensive because it uses less foam - concrete is cheaper than foam.

Spray foam is $2-3/board food applied (1 board foot = 1 sq. ft. x 1" thick), so 1 cu. ft. = 12 bd. ft. or $24-36/cu. ft. x about 30 to make a cubic meter - thus $720-1,080 for a cubic meter of foam. A cubic meter of Agilia is something like $150, and you're going to need a pumper anyway so ignore the cost of the pumper as the per meter 'pump charge' is negligible in the whole scheme of things.

Use a rotating laser to locate a point on the walls 2-4" above the high point of the foam, then snap a chalk line around the room at that height. This will be the pour line for the concrete.

Once the concrete is set, built a 2x3 or 2x4 cripple wall around the perimeter walls, install a few GFCI protected outlets (on a separate circuit) for convenience and a few fluorescent ceiling lights (all per code), and then skin the walls with drywall.

In all of this I am presuming that the existing 'foundation' wall is concrete. It it isn't (ie. maybe unfilled cinder block) then you need to check with a structural engineer to see if the amount of concrete you need to pump in will be exerting too much lateral force on the foundation walls. You should check with the engineer anyway and get a stamped drawing from him to CYA.

--- -------

Forgot to ask .... do you EVER get water over the bedrock when it rains or snow melts?
If you do, does it 'pool' or is the bedrock overall tilted in one direction so that the water flows to one (or more) sides of the foundation?
If it pools, how deep?
If it flows in one direction, how does it escape?

Either way, you may need to install foundation wrap on top of the bedrock BEFORE you foam. Here's a couple examples
»retail.armtec.com/en-ca/Products···rap.aspx
»www.deltams.ca/deltams_deltams.htm


RobThompson
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Hi Maynard %u2013 thanks for the detailed reply.

There are 2 areas where the water is coming in now, due to the spring melt. These areas are marked on the two middle photos here: www.dropbox.com/sh/c7ws0xe8a0b06···R38--L7Y

There is a sump pump installed to deal with the water infiltration marked in the first phone(the one where you see the blue well water pipe in the back ground). The water there comes in where the well water pipe & the under ground hydro conduit passes under the footing. The sump pump handles this area ok.

The second photo shows where the water comes in through the fissure/crack in the ledged bedrock. There is about 5 inches of water there now but it has been much deeper. I plan to drill and jack hammer a sump there and to install another pump. Unfortunately these two areas are some 40 feet apart.

As you can see in the second photo, there is a large area filled with crushed stone to level it. The depth of the stone is between 3 to 15 inches deep.

Water does not leak in anywhere on the high side of the bedrock floor, only on the low side. (right side)
--
Rob.
Blog: »googlevoiceforcanadians.com/
"Mankind" is a misnomer.

MaynardKrebs
Heave Steve, for the good of the country
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I get a 404 error in both Safari & Firefox for the link you posted. can't comment further until I can see the photos.

From the sounds of it, there's no F'ning way this house would have received an occupancy permit in Ontario, with running groundwater INSIDE the structure - though with the quality of builders & inspectors these days :-( you never know.

What are the existing foundation walls made of and how thick are they?


RobThompson
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1 edit
The walls are 8" concrete sitting on 16" wide footings that vary from 6 to about 20" thick. The footings are all sitting on, and are 'pinnied' to, the bedrock.

Try this link: »drive.google.com/folderview?id=0···=sharing


Msradell
P.E.
Premium
join:2008-12-25
Louisville, KY
reply to RobThompson
I can't get either one of the links to photos to open but you're going to have to do something to take care of the water issues before you spray any foam on anything. The idea of putting gravel to completely cover the bedrock and put the foam on top of it sound like it may be the way to go. You could leave a pit into the gravel for the sump pump you now have running. Looking at the pictures you posted earlier in the thread it looks like your property slopes down quite a bit. Could you just install a natural drain using gravity through the downhill side? That way if you ever lost power you wouldn't have to worry about your crawlspace flooding. If you use gravel you're going to have to be careful about walking on the spray foam, so you may have to put the concrete on top to give yourself a stable surface to walk on.
--
Written using Dragon NaturallySpeaking


RobThompson
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Lasalle, QC
Sorry, this link should work now: »drive.google.com/folderview?id=0···=sharing

dbamber

join:2003-02-07
Bandon, OR
reply to H_T_R_N
X2

patcat88

join:2002-04-05
Jamaica, NY
kudos:1

1 edit
reply to RobThompson
Exposed foam in your crawl space. Oh man, if I drop a candle in the crawl space, your house will be burning like a oil refinery in a couple minutes (the UL flame retardents in the foam work against cigarettes and metal cutting sparks, not continuous flame). Covered foam is bad in fires. Exposed foam is just napalm.

EIFS is also napalm. See video below

»www.youtube.com/watch?v=izNDNHK3_N8

MaynardKrebs
Heave Steve, for the good of the country
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reply to RobThompson
Saw the photos.

What a mess.

1) Your main floor beams appear to be supported on pressure treated wood columns.
Are the columns set into the concrete 'pads' or are they pinned (ie just sitting on top of the concrete pads with a metal pin/saddle holding them above the concrete? Wood - even PT wood, is not a long-term candidate for contact with concrete.

2) Due to the way the ground slopes in the basement and your desire for a level floor, you'd first need to toss in a lot of 3/4" crush limestone or river stone to level the area BEFORE concrete is poured. If you're lucky you'll be able to back a stone slinger truck up to the crawlspace window and shoot the stone into the crawlspace without you having to shovel it in one scoop at a time. »woodymammoth.com/woodworking/wp-···2126.jpg

3) That said (2) when you pour the concrete floor, you are going to trap a portion of your PT wood posts below the concrete, in an area which will have a constantly high moisture concentration. This is not a good long term thing for the underfloor portion of the posts. You may want to consider consulting with a structural engineer about installing some heavily epoxy-coated (to avoid corrosion failure) steel support columns bolted directly to bedrock before you go ahead with adding a concrete floor - because once you 'seal' the bedrock area with a concrete cap there isn't going to be ANY drying of the area below the floor via evaporation.

4) If you go ahead with the floor/gravel fill, I'd first wrap the below floor portion of the wood support columns with a couple of layers of peel-n-stick waterproofing membrane (offset any seams on opposite sides of the columns) and bring the membrane a couple of inches above the top of the new floor. I'd also try to spray/trowel some epoxy or fiberglass resin under the bottom of the wooden posts (I know this will be next to impossible) to try to seal the end grain against wicking water up.

5) One final thought - you could - instead of using spray foam- you could add 2" of ship-lap Styrofoam SM on top of the leveled gravel before you pour the concrete floor. It might be cheaper. Use 'Tuck tape' (the red housewrap vapor barrier tape) to tape any seams in the SM. The SM comes in 24" wide boards x 8' length - your crawlspace window might be too small to get them in though.


RobThompson
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said by MaynardKrebs:

What a mess.

I won't argue this point.

1) The PT columns are to pinned nor embedded - just sitting on top of the concrete pads.

Question: Should I 'swap out' the PT columns and replace them with metal jack posts?

2) I will only flatten the lower part. The higher & sloped part is all bed rock and there is no water penetration there. I would fill the 'low' points with crushed stone just to flatten it (the upper/high part) where I can.

3) The cement floor pour and/or spray will not exceed the top of any of the concrete 'pads', even after I place the crushed stone.

4) I will cover the tops of the concrete 'pads' with a couple of layers of peel-n-stick waterproof membrane.

5) I agree, I will use 2" EPS where ever possible and spray foam (2") all the non-flat areas. I will also cover the whole floor with thick poly before applying any of the foam.

Maynard, thank you very, very much for your guidance in resolving this problem - I truly appreciate you time and advice.
--
Rob.
Blog: »googlevoiceforcanadians.com/
"Mankind" is a misnomer.


PSWired

join:2006-03-26
Annapolis, MD
Are you trying to use this space for storage, or could you just insulate the floor, remove the HVAC, and provide exterior ventilation?

MaynardKrebs
Heave Steve, for the good of the country
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reply to RobThompson
said by RobThompson:

said by MaynardKrebs:

What a mess.

I won't argue this point.

Glad we're in agreement.

1) The PT columns are to pinned nor embedded - just sitting on top of the concrete pads.

Question: Should I 'swap out' the PT columns and replace them with metal jack posts?

In your case I'd consider it. Consult a civil engineer for column specs, and fastening method into the bedrock and attachment method to the beam. He/she may want to see a different concrete pad (size, thickness, strength) poured over the bedrock first.

2) I will only flatten the lower part. The higher & sloped part is all bed rock and there is no water penetration there. I would fill the 'low' points with crushed stone just to flatten it (the upper/high part) where I can.

3) The cement floor pour and/or spray will not exceed the top of any of the concrete 'pads', even after I place the crushed stone.

4) I will cover the tops of the concrete 'pads' with a couple of layers of peel-n-stick waterproof membrane.

5) I agree, I will use 2" EPS where ever possible and spray foam (2") all the non-flat areas. I will also cover the whole floor with thick poly before applying any of the foam.

Maynard, thank you very, very much for your guidance in resolving this problem - I truly appreciate you time and advice.

Don't use poly under the insulation - use the dimpled membrane I mentioned earlier, especially over the exposed bedrock. The reason for this is that the dimples create an air channel between the rock and the insulation layer. This allows any trapped moisture or running water to flow to the low point and presumably eventually weep out someplace. The spray foam / SM boards will be the air & moisture sealing layer - keeping moisture from getting up into the concrete floor and crawl space.

What type of insulation & thickness do you have on the underside of the main floor?


RobThompson
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Hi Maynard:

said by MaynardKrebs:

What type of insulation & thickness do you have on the underside of the main floor?

I do not have any insulation there at all as the crawl space is heated and included in the air exchanger system.

said by MaynardKrebs:

use the dimpled membrane I mentioned earlier

Sorry, I forgot that you had mentioned that - It is a great idea.

Rob.
--
Rob.
Blog: »googlevoiceforcanadians.com/
"Mankind" is a misnomer.

MaynardKrebs
Heave Steve, for the good of the country
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Since the 'floor' of the existing concrete is almost all effectively 'at grade' , I'm having second thoughts about the amount of insulation you may need.

Say your crawlspace was totally unheated, and let's say that you had 10" floor joists - then I'd recommend that you fill the 10" cavity with Roxul/fiberglass insulation (R35 or so) and then nail 2" of SM (R10) to the underside of the joists to prevent thermal bridging - for a total of about R45 in the floor. Your floor would never be cold.

Now lets consider the bedrock 'floor'. It's at/above grade. Part of it is actually exposed to the exterior. In the winter that bedrock is going to be really cold - far colder than a traditional basement where the floor is 4'+ below grade.

The reason I bring a traditional basement up is that in a traditional basement - where the slab is below the frost line, the ground temperature just below the slab is always above freezing. In most areas the slab is actually 5+' below grade, so the temperature under the slab is often 5-10 degrees C. Installing R10 under a slab in a basement like that will make the slab feel comfortable and reduce the amount of heating required to reach that comfort level.

However, in your case the bedrock is exposed and above grade, so it's going to get a lot colder than a below grade slab - in fact it will be just above or in fact freezing in parts, and act as a giant heat sink costing you a lot to heat it. You'll have to do some math about costs and heating savings and factor in your own comfort levels, but I'm now thinking that you' be better off installing 3-4" of foam instead of just 2". The extra insulation will also help reduce the possibility of condensation/mold in the crawl space.