Any builders here? Foundation advice

[Jonesy125]

I am in the process of building a cabin on our property. Footings and walls are done. 8”x16” footings, 48” x 6” ICF walls. I am planning to finish dry in next summer. My plan was to backfill now before doing the floor system without compacting, (I know this is advised against) and leave the foundation until next spring. How concerned should I be about leaving the crawl space side of the foundation exposed all winter? Should I insulate with hay to try to help with frost heaving? I could finish the floor system and tarp for the winter but I worry about moisture issues on the joists. (Will also cut into archery season) It has a full exterior drain tile in place and is located in southwest Montana. Any tips?

 

[rjthehunter]

Well nothing is going to stop the frost from heaving if it wants to. It looks pretty dry there.

Based on what I can see, I wouldn't be overly worried about any heaving. Do you know what the moisture content of the soil is?

If you decide to backfill, just make sure the material is dry. Otherwise you're going to have a lot of pressure pushing in on those walls once it's freezing.

 

[tillicant]

I'd backfill the outside, hay & tarp the inside., If is an area that gets a good amount of snow, that'll help.

 

[Jonesy125]

Well nothing is going to stop the frost from heaving if it wants to. It looks pretty dry there.

Based on what I can see, I wouldn't be overly worried about any heaving. Do you know what the moisture content of the soil is?

If you decide to backfill, just make sure the material is dry. Otherwise you're going to have a lot of pressure pushing in on those walls once it's freezing.

I don’t know moisture content but it is pretty dry. I understand your not supposed to backfill without the floor system in place I just figured uncompacted backfill would be less risky than the freezing.

 

[Jonesy125]

I'd backfill the outside, hay & tarp the inside., If is an area that gets a good amount of snow, that'll help.

Doesn’t get a ton of snow up there probably a couple feet on the level is normal

 

[trackerbacker]

My $0.02.

First, you're looking for straw, not hay, to bed the foundation. Semantics.

Next up, backfill, walls, sure, go ahead. Floors, this will be regional, but backfill it with you local media used, sand, rock etc. Toss some bedding on top. If you're worried, grab some insulated blankets and toss on top of straw once frost starts approaching.

Compacting AT THIS POINT AND REASON, bears no need. Get the media in, get it spread out. Move on.

Foolish to cap a foundation with wood and run through winter. You'll have delam issues, mold potentially, General uv damage. More so foolish to do that, then run propane to prevent heaving: moisture issues.

Draintiles are great, and without going into a diatribe on if they're just going to be gutter ddrains and/or a tie in etc, they'll pull moisture quite widely. That's a good step, but int/ext with tie ins, bedding (pea gravel ext at ftg or local media interior) will get it out and away. There are also benefits to an active radon sump with tie ins etc, pulls a lot of moisture out substructurally.

I'm guessing this is a diy project? You hanging the floor system or plating the floor system? What led you to a 6" wallset? What's the BP look like?

 

[rjthehunter]

I don’t know moisture content but it is pretty dry. I understand your not supposed to backfill without the floor system in place I just figured uncompacted backfill would be less risky than the freezing.

How long has the foundation been in place? If it's been awhile, the concrete should be cured enough. Just be gentle. I'd try to get at least a couple weeks of cure time if possible before backfilling. I've seen backfilling take place as soon as a couple of days after being poured (also seen walls ruined because of this). A month would be ideal... That's when concrete reaches it's full design strength.

 

[trackerbacker]

How long has the foundation been in place? If it's been awhile, the concrete should be cured enough. Just be gentle. I'd try to get at least a couple weeks of cure time if possible before backfilling. I've seen backfilling take place as soon as a couple of days after being poured (also seen walls ruined because of this). A month would be ideal... That's when concrete reaches it's full design strength.

Truth

 

[BigHornRam]

Brace the back wall before backfill, would be a good idea. Blankets and straw on the inside, good idea.

 

[Jonesy125]

My $0.02.

First, you're looking for straw, not hay, to bed the foundation. Semantics.

Next up, backfill, walls, sure, go ahead. Floors, this will be regional, but backfill it with you local media used, sand, rock etc. Toss some bedding on top. If you're worried, grab some insulated blankets and toss on top of straw once frost starts approaching.

Compacting AT THIS POINT AND REASON, bears no need. Get the media in, get it spread out. Move on.

Foolish to cap a foundation with wood and run through winter. You'll have delam issues, mold potentially, General uv damage. More so foolish to do that, then run propane to prevent heaving: moisture issues.

Draintiles are great, and without going into a diatribe on if they're just going to be gutter ddrains and/or a tie in etc, they'll pull moisture quite widely. That's a good step, but int/ext with tie ins, bedding (pea gravel ext at ftg or local media interior) will get it out and away. There are also benefits to an active radon sump with tie ins etc, pulls a lot of moisture out substructurally.

I'm guessing this is a diy project? You hanging the floor system or plating the floor system? What led you to a 6" wallset? What's the BP look like?

Yes this will be 100% diy, no I’m not even close to a carpenter. I chose 6” ICF walls because I cannot get a concrete truck to my site and used skidsteers with concrete buckets for the pours. I’m not sure what you mean by plating or hanging but floor joists will be resting on the sill plate with a center girder beam. Cabin is 28x36 single level. This is a weekend recreational cabin about 45 min from home. Exterior drain tile is full perimeter, gravel above and below to a drain pipe out the front side

 

[Jonesy125]

Tru

How long has the foundation been in place? If it's been awhile, the concrete should be cured enough. Just be gentle. I'd try to get at least a couple weeks of cure time if possible before backfilling. I've seen backfilling take place as soon as a couple of days after being poured (also seen walls ruined because of this). A month would be ideal... That's when concrete reaches it's full design strength.

Footings poured in July walls poured Aug 4th

 

[BigHornRam]

Yes this will be 100% diy, no I’m not even close to a carpenter. I chose 6” ICF walls because I cannot get a concrete truck to my site and used skidsteers with concrete buckets for the pours. I’m not sure what you mean by plating or hanging but floor joists will be resting on the sill plate with a center girder beam. Cabin is 28x36 single level. This is a weekend recreational cabin about 45 min from home. Exterior drain tile is full perimeter, gravel above and below to a drain pipe out the front side

Drop joist systems are popular now, if you want to leave out entry steps. Less siding too.

 

[rjthehunter]

Footings poured in July walls poured Aug 4th

You should be good then. Just give it another full week. Then you could even compact it lightly too. Just don't beat the hell out of it when compacting! Being is it's only 4' walls it's not as prone to being pushed in as a 8-12' wall is!

 

[Jonesy125]

Thanks for the info guys, I still have a board running the perimeter inside from my pour bracing so I can brace it from the inside very easily. Kinda concerned it will be a swimming pool come spring melt but not a lot I can do at this point if the consensus is that it’s a bad idea to joist and tarp

 

[Addicting]

When you do the floor, put plastic and then 1” pink insulation board on the bottom of the joists before decking it. Makes a world of difference on moisture, gas, and cold creeping up thru the floor.

 

[Gerald Martin]

If it were me I would skip the straw on the inside. You already have two inches of foam on the interior with the ICF’s.
Come spring that’s going to be a mess of half rotten soaked material you’ll have to clean out.

Backfill it gently and call it good.

One thing about hanging the floor system rather than sitting it on the plate to consider is whether you will have your crawl space heated or not and whether you will need it vented.
If you’re not going to heat the crawl space you will want to vent it to the exterior and if you hanger the floor system that makes venting very difficult unless you poured foundation vents into your walls.

Everything I have seen with a hangered floor system has been with a heated crawl space. I heated my crawl and love it for the fact that it’s always dry and makes for great storage.

 

[BigHornRam]

If it were me I would skip the straw on the inside. You already have two inches of foam on the interior with the ICF’s.
Come spring that’s going to be a mess of half rotten soaked material you’ll have to clean out.

Backfill it gently and call it good.

One thing about hanging the floor system rather than sitting it on the plate to consider is whether you will have your crawl space heated or not and whether you will need it vented.
If you’re not going to heat the crawl space you will want to vent it to the exterior and if you hanger the floor system that makes venting very difficult unless you poured foundation vents into your walls.

Everything I have seen with a hangered floor system has been with a heated crawl space. I heated my crawl and love it for the fact that it’s always dry and makes for great storage.

The straw and blankets would keep frost penetration to a minimum under the footings during the winter. I've never left a foundation sit through the winter, so not sure how much damage would take place doing that. Little extra protection doesn't hurt.

 

[Jonesy125]

The straw and blankets would keep frost penetration to a minimum under the footings during the winter. I've never left a foundation sit through the winter, so not sure how much damage would take place doing that. Little extra protection doesn't hurt.

Agree with both of you the minimum cost of straw would at least give me piece of mind but also clean out would suck. It is going to be an unheated vented crawl space. It’s pretty much an April-November type cabin. Will have water, septic, power but will be winterized yearly.

 

[rogerthat]

If you put the correct amount of steel in your foundation then you got nothing to worry about. Lightly backfill, ensure you have positive drainage, and let it ride. The foundation will handle the heave with no issue. Frost heaving won’t be an issue if your soils are dry anyway. You will be good to go to start back up next year. Don’t overthink it.

 

[Mallardsx2]

I would pull the forms, spray that bitch with hot tar inside and out, make sure it had an outlet to drain and leave it just like that until spring.

Other than the tar, I wouldn’t waste another dime on it until then.

But that’s just me.