The location is central Maine.  We're thinking about a piece of property, but realize it is not possible to get a house up by winter this year.  I've done enough research to know that there is just too much to do between now and the start of the build.

So I'm wondering if you can get the pad in by October and start building in the spring.  I know how to frame a house, but I know nothing about cement/concrete.  Around here everyone has basements, so not a lot of examples from which to draw.  However, that is changing with newer built homes.

Can you safely "winter over" the FPSF?

Thanks.

Yes. Its no different than an unheated garage but you'd want to make sure your rough grade would take care of spring runoff, pad prep with correct material and compaction is what's important. If you're worried call your inspector or if you don't have one, the closest inspector to confirm it has been done in your climate, I've done it in climate 6/7.

Not a concrete expert but think it should be possible. I would have two main concerns.

One would be degradation of the insulation if not back filled, covered, and protected from the elements.

The other would be moisture content in the concrete slab during the freeze thaw cycles. Here is a link to a discussion of concrete moisture drying times. After 28 days your pretty well dry and after 60 days additional drying is infintisimal. I think I would allow for 60 days drying and cover it up with a robust plastic well in advance of the first freeze. https://www.nrmca.org/aboutconcrete/cips/28p.pdf .

You might want to install your wing insulation, sloped away from slab and leave the slab covered in curing blankets as an insurance policy.

I thought up there you had to build the pad below frost line, around 4' is why everyone goes down a little farther to make a basement. Why not have a basement? Maybe something has changed that I'm not aware of with pads up north.

The biggest concern would be spauling. All back filling should be done and your drainage has to be perfect. Frost heaves because of water in the ground. You sure your sold on a pad. Where I am in NY from time to time builders will build on a slab and I can tell you those houses have a reduced value. I've had customers blast and use a excavator with a demo. point just to get a 7' high basement in. I think you should reconsider. Someday that house will be sold and if the majority of houses have basements then yours will take a hit.

Posted By robinnc on 07 Apr 2017 05:25 AM
I thought up there you had to build the pad below frost line, around 4' is why everyone goes down a little farther to make a basement. Why not have a basement? Maybe something has changed that I'm not aware of with pads up north.

Frost protected shallow foundation.

Posted By smartwall on 07 Apr 2017 08:48 AM
The biggest concern would be spauling. All back filling should be done and your drainage has to be perfect. Frost heaves because of water in the ground. You sure your sold on a pad. Where I am in NY from time to time builders will build on a slab and I can tell you those houses have a reduced value. I've had customers blast and use a excavator with a demo. point just to get a 7' high basement in. I think you should reconsider. Someday that house will be sold and if the majority of houses have basements then yours will take a hit.

I'm not totally sold on a pad, but now it costs more money to build basement space than above ground.  Houses without basements have reduced value because there is less there and they cost less to make.  However, I am aware of that syndrome where a house's resale can be reduced below its value because of, "Oh, no basement...".

I've been house shopping and I can tell you that almost all of the basements I've been in have been worse than useless.  Nothing around here got insulated at all when built until maybe 10 years ago or so.  At least half of them are wet (spring is a good time to house shop for this reason - all sorts of drainage problems show themselves), none of them have been suitable as any kind of work space - storage at best.

I'm also retired and would like to stay away from stairs.  I'm not totally against them, but want my main living areas on one floor.  Work spaces and storage could be on another.  My wife and I just want a simple house, but we want it comfortable.  We also need it to be as cost effective as possible without compromising on decent structure integrity, insulation, air tightness, etc.

We have also been incredibly discouraged at the lack of knowledge for anything beyond traditional 2x6 framing.  The last young contractor I spoke with didn't know anything about FPSFs.  He was supposed to be all up with "the new stuff".  I asked him if he had any experience with frost protected shallow foundations.  I got, "Well, what do you mean...I mean, like, all foundations have to be frost protected..."  I thanked him for his time and got off the phone.

Have you considered an unvented insulated crawlspace foundation with ICF stem walls and footing poured to below the frost line? Much less excavation involved than a full basement. The ICF stem wall and footing can be poured at the same time. This is often called a monopour (smartwall can tell you all about this). Pour support pads for piers at the same time as the foundation walls. Backfill & level inside foundation walls as required. Install block piers. Place rigid insulation and vapor barrier on ground. Pour 2"-3" rat slab.  Install floor framing.

An advantage of this is that a wood floor system is much more forgiving on your knees and joints as you get older. Plus you retain access to your plumbing and mechanical that is run under the floor system. Depending on the type of heating/cooling system, you may be able to use the crawlspace as a return air plenum.

Have you looked into ICF? I've heard they are around the same price as 2x6 or even less. VERY energy efficient!  ALLOT less labor involved. I've never heard a frost protective before.

Posted By arkie6 on 08 Apr 2017 06:26 PM
Have you considered an unvented insulated crawlspace foundation with ICF stem walls and footing poured to below the frost line? Much less excavation involved than a full basement. The ICF stem wall and footing can be poured at the same time. This is often called a monopour (smartwall can tell you all about this). Pour support pads for piers at the same time as the foundation walls. Backfill & level inside foundation walls as required. Install block piers. Place rigid insulation and vapor barrier on ground. Pour 2"-3" rat slab.  Install floor framing.

An advantage of this is that a wood floor system is much more forgiving on your knees and joints as you get older. Plus you retain access to your plumbing and mechanical that is run under the floor system. Depending on the type of heating/cooling system, you may be able to use the crawlspace as a return air plenum.

I have not looked into and unvented crawlspace foundation.  I'm trying to keep it passive solar and that would pretty much eliminate that.  It sounds like the price would be right in the middle between a FPSF and a full basement.  I'm guessing the piers would be for the central beam for the floor joists, say, in a typical ranch?  Also, I'm leery of ICFs and SIPs because of carpenter ants.

I will look into that, but after all that would it really be much more to build an ICF basement?

Posted By robinnc on 09 Apr 2017 04:35 AM
Have you looked into ICF? I've heard they are around the same price as 2x6 or even less. VERY energy efficient!  ALLOT less labor involved. I've never heard a frost protective before.

Yes, I have looked into ICF a bit and am going to make a couple of calls to the only two builders within a reasonable range.  However, as I stated above, it is reported that carpenter ants like to make nests in the foam.  I've also heard they are the same price as a 2x6 frame, and I've also heard that's a load of bull and they're a lot more.  I'll only know when I get a firm price on a dried in building.  Some builders won't do that around here.  They will only do start to turnkey.

If you've never heard of it before, just google "frost protected shallow foundation".  It's becoming quite mainstream, especially now that code demands all basements be insulated, skinned and drained properly.  You can't just dig a hole and pour cement walls anymore.  I think that's a good thing.

I agree about the basement. I can't imagine one built without those. I'll do a 'Bing' search.

If you quote an unvented crawl that yields no real useable square footage so it inflates your cost per finished square foot, then quote a full basement and include it as useable square footage the full basement becomes a bargain. Unless you're in rocks the cost to dig an extra 4' and the cost for 4' of poured wall isnt that much compared to the square footage you gain.

You do an unvented crawl right your still doing the same footings, same draintile, same washed base rock, same slab and your trades will charge you more because their working on mechanics creepers down their.

If you want an FPSF, which will take a devalue because you dont have that extra storage space basement people are used too, you'll save your devaluation in your foundation savings anyways. Find a reputable flatwork contractor and provide him with a detail or cross section if he has no experience and they will figure it out, its not rocket science, they will just want to know how the foam integrates, foam type to use, Ect. You tell them how you want it, then they wont feel the liability of trying something new because you provided the plans.

If you quote an unvented crawl that yields no real useable square footage so it inflates your cost per finished square foot, then quote a full basement and include it as useable square footage the full basement becomes a bargain. Unless you're in rocks the cost to dig an extra 4' and the cost for 4' of poured wall isnt that much compared to the square footage you gain.

You do an unvented crawl right your still doing the same footings, same draintile, same washed base rock, same slab and your trades will charge you more because their working on mechanics creepers down their.

If you want an FPSF, which will take a devalue because you dont have that extra storage space basement people are used too, you'll save your devaluation in your foundation savings anyways. Find a reputable flatwork contractor and provide him with a detail or cross section if he has no experience and they will figure it out, its not rocket science, they will just want to know how the foam integrates, foam type to use, Ect. You tell them how you want it, then they wont feel the liability of trying something new because you provided the plans.

Basements are more a cultural thing than a real thing. In the southwest nearly everything goes on a slab--only recently insulated--and only when expat Midwesterners come around on nearly useless "crawl spaces". You can get more area under one roof if that is what you are after. We have seen more modest houses built on one level for folks in the retirement mode.

In Sweden, Norway and Finland the frost protected shallow foundation is the norm. Don't listen to the naysayers unless they can show you some of the FPSF,s they have done, or even one, so called, "failure". Your area too cold? Does it get cold in Sweden? In parts of Alaska and Canada, where permafrost lives, all foundations are insulated and round every lake shore, etc.

One of the first jobs I worked with my father was a very early 70's slab-on-ground house near Madison Wisconsin. This was a "super insulated" house on grade with no exterior perforations save the main plumbing vent, modestly sized "double-pane" windows etc. It was the first house I was in that was heated by the lighting most of the year. I have since consulted on many radiant slab-on-ground floor systems installed in Frank Lloyd Wright homes in that same area where he and I both spent a lot of time--though not together.

We regularly design hydronic based HVAC systems for FPSF home, shops and barns. There is nothing more comfortable or efficient.

https://www2.cs.arizona.edu/people/jcropper/desguide.pdf

http://www.greendesignbuild.net/Pages/FrostProtectedShallowFoundationsareaResourceEfficientDesignforFoundationsinUSClimates.aspx

You should build the house you want, unless someone else is paying for it. This is still the USA. If "they" want a basement (quaint vestige of the root cellar) let "them" dig one. If you are building for resale, you are in the wrong forum.

With all the money you save with FPSF/no-basement, you can build a bigger garage, attic storage and house. Higher valuation and no water problems. On the other hand, I like the look of an elevated front door (that many slab on grade homes don't have).

To answer your question, there are two types of FPSF. An unheated design does not rely on any heat from the building and can safely "winter over".

"On the other hand"

I think that's one of Jonr's favorite statements.... Lol

Someone told me that all issues have two sides - so I try :-).

Posted By jonr on 11 Apr 2017 04:03 PM
With all the money you save with FPSF/no-basement, you can build a bigger garage, attic storage and house. Higher valuation and no water problems.

I cant tell if you are being serious or if its a joke I dont get. Depending on site conditions, even best case your savings could maybe, maybe buy you a third stall on your garage. You might save 60% versus a full useable foundation. You cant beat a basement price per square foot. Second, higher valuation will always be with a basement despite that "third stall savings." Third, basements dont have water or moisture problems. If they do you/contractor/builder f'd it up. Basement bad rap of musty mildew space is from the block wall, clay tile era, site backfill. Codes and common sense address water management and provide the cheapest square footage you can buy. That said, if the OP wants a FPSF go for it. PS, dont waste your time with ICF unless you like burning money.