# Frost wall ?



## joecaption (Nov 30, 2011)

In your area no way would I try and build a 3 season porch on piers.
I'd just pore footings and build a real foundation.
Less chance of it settling and pulling away from the house.
By going with a slab floor it's going to limit your flooring options.


----------



## Jim McC (May 22, 2013)

Thanks Joe. Can a frost wall be done with the drain pipe down there? 

With a concrete floor, what flooring options do we have other than tile?


----------



## joecaption (Nov 30, 2011)

Here's a picture of a frost wall.
As cold and as low as the frost line is in your area I still do not see this as a great idea.
If you need your flooring 18" above grade I see no point in building it as a frost wall foundation.
Might be fine for a garage, or a slab foundation house.


----------



## Jim McC (May 22, 2013)

joecaption said:


> In your area no way would I try and build a 3 season porch on piers.
> I'd just pore footings and build a real foundation.


What do you mean by a "real foundation"? The building inspector also suggested a frost wall and a concrete floor.


----------



## GBrackins (Apr 26, 2012)

Jim McC said:


> I have no idea what a frost wall is. The depth would need to be 48" deep. The deck floor is only about 18" above grade. Porch will be 12' X 19'.
> 
> 1) One problem is: A drain pipe runs under the current deck to our septic tank(which is near one corner of the deck). Can a frost wall be used with the drain pipe down there?
> 
> ...


*a frost wall is a foundation wall (either concrete or concrete block) where the footing would be set below your frost line. this would be in place of the pier footings. If installed on the 3 sides of your room this would provide an enclosed area below the floor. this would help to prevent wind from blowing under the floor helping to keep it warmer. if you go this route I'd recommend a vapor barrier below a concrete slab. this helps to control moisture issues. cut an opening from your basement into this space and it could be used for storage.

realize this is not full height since the slab is only about 48" below grade, you could always make this a full basement (taller concrete walls) to provide additional storage/usable space.

remaining answers are shown above

Good luck!
*


----------



## Jim McC (May 22, 2013)

Thanks again. The porch will butt up to 2 right angle walls, so there would only be 2 frost walls if we did that.


----------



## concretemasonry (Oct 10, 2006)

Very often plan and code people recognize that a "3 season porch" can be slipped in later and becomes a "4" season addition. If you don't follow the suggestions the home may be on a future watch list for conversions and change of use. Having 2 exterior walls on a home is a little unusual and if the area is converted, you could be facing some different code and structural situations. - If you do not convert, you should have no code problems since you have fully approved sun porch following the suggestion of the code officials.

Local code officials have every right to exceed the model codes (they are just minimum standards), just as every state or jurisdiction may do.

Dick


----------



## GBrackins (Apr 26, 2012)

so true Dick, they are not always as dumb as they seem .....


----------



## Jim McC (May 22, 2013)

concretemasonry said:


> Having 2 exterior walls on a home is a little unusual... Dick


What do you mean by this?


----------



## stadry (Jun 20, 2009)

consider putting some heat in the floor,,, warm floors are VERY kind to cold tootsies :laughing: polish, acid-stain, or dye conc,,, install engineer'd wood flooring, carpet, tile, OR area rugs


----------



## jomama45 (Nov 13, 2008)

Jim McC said:


> While at the local lumberyard today, the guy recommended a frost wall for the 3 season porch we want to build. That way we can have a concrete slab floor, and also insulate the sides and under the slab. I have no idea what a frost wall is. The depth would need to be 48" deep. The deck floor is only about 18" above grade. Porch will be 12' X 19'.
> 
> 1) One problem is: A drain pipe runs under the current deck to our septic tank(which is near one corner of the deck). Can a frost wall be used with the drain pipe down there?
> 
> ...


Generally, YES, but it really depends on what type of decking you're thinking of. A lot of the low-maintenance decking is extremely expensive. That said, there's a few different small steps involved for such a small foundation, so it's not that cheap for a pro to come in and pour a yard or two of concrete at a time, wait a day or two, come back and set 100 block, wait a few days, etc.....


----------



## Jim McC (May 22, 2013)

jomama45 said:


> Generally, YES, but it really depends on what type of decking you're thinking of. A lot of the low-maintenance decking is extremely expensive. That said, there's a few different small steps involved for such a small foundation, so it's not that cheap for a pro to come in and pour a yard or two of concrete at a time, wait a day or two, come back and set 100 block, wait a few days, etc.....


Thanks. Where are you located in Wisconsin? Do you see any problem building a 3 season porch(butting up against 2 right angle walls) with concrete pier footings? Using sonotubes 48" deep? Floor will be about 18" above grade.


----------



## GBrackins (Apr 26, 2012)

if you decide to go that way I'd put an inch or rigid insulation under the joists and then 1/2" plywood or building wrap. make sure to seal all seams, you don't want the cold wind whipping in the corner to come inside.

we do sonotubes set 48" deep here all the time for sunrooms/3 season rooms. cold floors is the biggest complaint that's the reason I use the rigid insulation, provides a thermal break between the wood joists and the exterior.

make sure you put the vapor retarder (kraft paper backing) towards the warm-in-winter side of the floor.


----------



## Jim McC (May 22, 2013)

GBrackins said:


> if you decide to go that way I'd put an inch or rigid insulation under the joists and then 1/2" plywood or building wrap.


It's going to be impossible to get under the joists though.


----------



## MTN REMODEL LLC (Sep 11, 2010)

GBrackins said:


> *a frost wall is a foundation wall (either concrete or concrete block) where the footing would be set below your frost line. this would be in place of the pier footings. If installed on the 3 sides of your room this would provide an enclosed area below the floor. this would help to prevent wind from blowing under the floor helping to keep it warmer. if you go this route I'd recommend a vapor barrier below a concrete slab. this helps to control moisture issues. cut an opening from your basement into this space and it could be used for storage.*
> 
> _*realize this is not full height since the slab is only about 48" below grade, you could always make this a full basement (taller concrete walls) to provide additional storage/usable space.*_
> 
> ...


Gary... I'm from snow country... and a frost wall is new to me.

If I'm understanding correctly, it's sorta a half height (freeze depth) basement.

What's it's benefit over a perimeter/stem wall foundation.?

Why have a concrete slab at it's bottom... eccept for possible storage.

And why is the OP inquiring as to flooring optiions in his sunroom, which I presume would be framed conventionally with plywood subfloor.

I'm really missing something here.

TIA


Peter


----------



## TheEplumber (Jul 20, 2010)

In regards to your drain line- be sure it is upgraded to whatever is approved in your area. usually pipes within the footprint of the structure needs to be sch.40 DWV plastic. Outside the footprint pipes can be a lessor grade- and the tank, in my area, needs to be at least 10' away from the structure. 
The pipe can go through the wall- no problem


----------



## GBrackins (Apr 26, 2012)

MTN REMODEL LLC said:


> Gary... I'm from snow country... and a frost wall is new to me.
> 
> If I'm understanding correctly, it's sorta a half height (freeze depth) basement.
> 
> ...


a frost wall has it's footing below the frost line, in the OP's case I'm guessing it's 48" the same as in Massachusetts. I think it's one of those local terms, like the use of sonotube foundation instead of pier foundation, as you can construct a round pier foundation without using sonotube brand products.

a full height wall in my area is about 8' (7'-9" to 7-10"). a frost wall in my area typically is about 4'- to 5' in height (depends on how high the top of foundation is above the adjacent grade).

the benefit would be less cost over a full height foundation wall especially when someone does not want or need more basement.

a concrete is usually placed to help prevent moisture issues as the enclosed space has to be accessible, either through a hatch in the floor, or an opening from their basement.

I thought they were asking about flooring options for the concrete slab, since they wouldn't have much headroom when using a frost wall they don't really have much of an option to be cost effective.

Now with that said I normally recommend to clients to go with a full height foundation wall unless their foundation is only a frost wall (4' depth of footing).

no I don't think you're missing anything, like I said it's more of a local term. I never heard of a frost wall until I moved to Massachusetts.


----------



## Jim McC (May 22, 2013)

MTN REMODEL LLC said:


> Gary... I'm from snow country... and a frost wall is new to me.
> 
> If I'm understanding correctly, it's sorta a half height (freeze depth) basement.
> 
> ...


----------



## MTN REMODEL LLC (Sep 11, 2010)

GBrackins said:


> a frost wall has it's footing below the frost line, in the OP's case I'm guessing it's 48" the same as in Massachusetts. I think it's one of those local terms, like the use of sonotube foundation instead of pier foundation, as you can construct a round pier foundation without using sonotube brand products.
> 
> a full height wall in my area is about 8' (7'-9" to 7-10"). a frost wall in my area typically is about 4'- to 5' in height (depends on how high the top of foundation is above the adjacent grade).
> 
> ...


:thumbsup::thumbsup::thumbsup:

Gary...What a great, informative, understandable response. Thank Ya

(You are correct... difference in terminology... didn't know it... but I've built a couple)

Best 

Peter


----------



## GBrackins (Apr 26, 2012)

I apologize Jim, I didn't realize your room was going to have a concrete slab as floor, I was thinking it was going to be wood framed.


----------



## jomama45 (Nov 13, 2008)

For me, there's 3 kinds of general residential foundations common here:

- Full basement: 7-10' high typically, with soil on the outside and clear space on the interior.

- Crawlspace foundation: Typically 4' high walls with soil on the outside, and clear space on the interior.

- Frost wall/stem wall foundation: Typically 3'4" to 4' high, with balanced fill on both sides, no access to the interior side, and typically a concrete floor/cap/stoop on top. This style is the most common foundation for stoops/porches/attached garages in this area.....


----------



## jomama45 (Nov 13, 2008)

Jim McC said:


> Thanks. Where are you located in Wisconsin? Do you see any problem building a 3 season porch(butting up against 2 right angle walls) with concrete pier footings? Using sonotubes 48" deep? Floor will be about 18" above grade.


I'm in Oz. County.

No real problem other than the insulation issues, if that even is an issue for you.....

Obviously, a frost wall foundation is a better long-term approach, but it's entirely your choice........:thumbsup:


----------



## MTN REMODEL LLC (Sep 11, 2010)

In Co, we'll do it both ways, depending on *site location primarily*.

In the mountains, obviously we have signifigant elevation / slope on our footprints.

Pier/post is often done as our finish floor is 6-8-10- above grade... too much stem wall to form. Often floor joists are over spected just to provide greater insulation.

Obviously, a full spreadT footer/stem wall (frost basement at whatever height) provides a better insulation barrier, and a foundation adequet for two story. (Plus the potential for storage and depending on grading minus the possibility of water intrusion)

For a single story sunroom or 3 season room addition, it seems primarily a tradeoff of initial cost vs insulation quality costs down the road, assuming equal aesthetic considerations. We go 48 frost depth with footers or piers, and there is really not a structural issue as we are on decomposed granite in the mountains.


----------



## Jim McC (May 22, 2013)

GBrackins said:


> I apologize Jim, I didn't realize your room was going to have a concrete slab as floor, I was thinking it was going to be wood framed.


Not necessary. I don't know if the floor will be concrete or not.


----------



## Jim McC (May 22, 2013)

I got my first quote today for a frost wall(one 10' wall, and one 19' wall), and a 10' X 19' slab. $4,156, plus $260 for 1" insulation, and $360 for 2" insulation. There's only 2 walls because the porch will butt up against 2 right angle walls. Is this price in the ballpark? I'm going to get a couple more quotes. Thanks.


----------



## GBrackins (Apr 26, 2012)

well you'll know more when you get in your other estimates


----------



## Jim McC (May 22, 2013)

GBrackins said:


> well you'll know more when you get in your other estimates


Right. I assume I should go with the 2" insulation? What do most people do with the outside of the block wall to make it look better? It will be about 16" above grade.


----------



## GBrackins (Apr 26, 2012)

you could always setback your foundation so that you could apply the 2" rigid insulation and then run your sheathing down to grade. I'd use PT sheathing along the bottom, put on your building wrap and your exterior siding. tapcon the sheathing into the blocks.

somebody else might have a better idea as we do not use concrete block in my area for foundations (at least I haven't seen it done in many years).


----------



## Jim McC (May 22, 2013)

I talked to an architect who advised against using a frost wall and slab. He said the floor will always be cold(even with 2" insulation under slab and on the 2 frost walls). He suggests concrete pier footings and insulating the largest joists that will fit(floor is only about 16" above grade). Do you agree?

A carpenter/home builder that came out today, suggested a frost wall with a 2X6 treated sill on top, then "I-joists" sitting on the sill plate. He said the joists don't have to be treated lumber. I thought the joists had to be treated because they will be pretty close to grade? The floor height will only be about 16" above grade.


----------



## stadry (Jun 20, 2009)

this is why i like this place - replacing my ignorance w/knowledge is a good thing :yes:

thought the sill plate had to be p/t - rim joist i don't know,,, floor joists can be reg spf 2x10 16" o/c or =,,, insulation won't keep something warm OR cold - it just restricts the movement of either to the warmer side as cold always runs to heat

anything below skin temp feels cold to most, right ?

why not call in another carpenter ? i never saw 2 of 'em agree on anything :laughing: ever !


----------



## Jim McC (May 22, 2013)

Thanks. A couple more carpenters are coming out this week. The concrete guys don't agree either. 2 guys are suggesting a frost wall, and another guy and an architect are recommending concrete pier footings. I'm confused.


----------



## GBrackins (Apr 26, 2012)

Jim,

I've attached a sketch of what I am talking about. give it a look see ....


----------



## Jim McC (May 22, 2013)

Thanks Gary. I know what you're talking about, but we have no desire or need for another crawl space. I forgot to mention earlier that the one wall(19' wall) is not a full foundation. It's a half foundation wall(crawl space). Does that have any bearing on whether we should use a frost wall or pier footings? The other wall is a full foundation.

At this point, we are leaning toward a frost wall and a concrete slab floor. We may leave it exposed as the finished floor, with an etched or polished surface. I have a concrete guy coming today, who also does this, and is highly recommended.

If we do a frost wall and slab floor, is it best to also do concrete steps? The floor height is currently 16" above grade, but I was told we may have to do a step down(out of patio door) because we have a low slope roof. This would also help with ceiling height in porch.


----------

