OT: Home Construction Advice

[Jeffreauxdawg]

Looking to build an addition to my home. We have heavy snow loads in this area and that means you have to not only increase the strength of the roof system and beams, but also the foundation. We have around 36" of frostline here so the foundation footers have to be deeper than that. Typically, foundations in this area are crawlspace, with some basements. But in the last year or two contractors are only using insulated slab foundations.

Anyhow, the city/county is requiring an engineer to stamp the plans. The engineer is making me use the insulated slab even though I don't really trust the system because we have no idea if it will last long term. Insulated slabs are apparently now required. I don't want to live in a home with an unproven foundation. I just want build a good old traditional crawlspace. Should I just find a contractor that will help me build it without a permit? What are the consequences of building without a permit?

Have any of you SPS'ers had any negative experiences from insulated slab foundations?

And why in the hell do these building codes exist in the first place? Why does anyone give two ***** on how I build my addition. Build your home any way you would like. I will build mine however I damn well please, without unproven methods.

 

[johnson86-1]

Looking to build an addition to my home. We have heavy snow loads in this area and that means you have to not only increase the strength of the roof system and beams, but also the foundation. We have around 36" of frostline here so the foundation footers have to be deeper than that. Typically, foundations in this area are crawlspace, with some basements. But in the last year or two contractors are only using insulated slab foundations.

Anyhow, the city/county is requiring an engineer to stamp the plans. The engineer is making me use the insulated slab even though I don't really trust the system because we have no idea if it will last long term. Insulated slabs are apparently now required. I don't want to live in a home with an unproven foundation. I just want build a good old traditional crawlspace. Should I just find a contractor that will help me build it without a permit? What are the consequences of building without a permit?

Have any of you SPS'ers had any negative experiences from insulated slab foundations?

And why in the hell do these building codes exist in the first place? Why does anyone give two ***** on how I build my addition. Build your home any way you would like. I will build mine however I damn well please, without unproven methods.

That's going to be very location dependent, both how likely it is you can get away with it to begin with and also what happens if it is discovered later.

Also, the first thing I would do is find another engineer. Surely the code still allows conventional foundations, right?

 

[Grove Sh*tter]

I believe they can refuse to allow you to buy utilities if you go rogue in Mississippi. That sucks.

 

[horshack.sixpack]

Pretty sure that permitted building requires inspections to code. Unpermitted building might yield: A) a contractor that is crap with no recourse AND/OR B) someone reporting it and having to stop to get permitted/possibly rip out progress AND/OR C) the additional space being a net negative on a future inspection to sell, thus reducing the value of your home because it may have to be ripped/replaced to bring to code.

That being said, we don't know the possible long term side effects of insulated slabs...

 

[Shmuley]

At some point a lender or insurer or utility provider or subsequent purchaser without notice will be involved in some way with this structure. If at any point it becomes apparent that the structure was not permitted, the consequences could be sucky.

 

[Jeffreauxdawg]

Engineer called me back. Really informative conversation.

My fear around a slab foundation was strictly related to potential frost heaving. Simply put, when soil freezes, it expands and would move the foundation. In a crawlspace you are building on footers below the potential frost line and using the heat from the building to heat the soil inside the exterior stem walls to help keep it warm as well. The pony walls resting on the footers are holding up the house. The potential negatives of the crawl space are moisture issues in the crawlspace and having to heat the area.

Well it turns out, insulated slabs are also called FPSF (Frost Protected Shallow Foundations) and were originally conceived by Frank Lloyd Wright in the 1930's. While not widely adopted in the US, they have been used for decades in Alaska and millions of homes in Norway, Sweden, and Finland are on FPSF construction. The idea is that ground only freezes from exposure to the cold outside air. So you insulate the exterior of the slabs to keep the cold air away from the soil underneath the slab. Geothermal warmth is then captured and it not only prevents the frost heaves, but is also considerably more energy efficient since you no longer have to heat all of that cool air in the crawlspace. No risk of moisture issues. Overall, it considerably outperforms a crawlspace.

I feel much better now. I did ask and the engineer and he verified his house is on a FPSF and only in very rare circumstances (such as building on extreme slopes) would he use crawlspace or basements. It would appear the engineers are the experts and really know what they are talking about. I guess I got worked up trying do my own research on a subject I was unfamiliar with and reacted to anecdotal evidence from friends and unknown internet posters.

 

[RocketDawg]

There might be issues with getting the addition (and maybe the entire house) insured as well.

 

[wsjmsu75]

Engineer called me back. Really informative conversation.

My fear around a slab foundation was strictly related to potential frost heaving. Simply put, when soil freezes, it expands and would move the foundation. In a crawlspace you are building on footers below the potential frost line and using the heat from the building to heat the soil inside the exterior stem walls to help keep it warm as well. The pony walls resting on the footers are holding up the house. The potential negatives of the crawl space are moisture issues in the crawlspace and having to heat the area.

Well it turns out, insulated slabs are also called FPSF (Frost Protected Shallow Foundations) and were originally conceived by Frank Lloyd Wright in the 1930's. While not widely adopted in the US, they have been used for decades in Alaska and millions of homes in Norway, Sweden, and Finland are on FPSF construction. The idea is that ground only freezes from exposure to the cold outside air. So you insulate the exterior of the slabs to keep the cold air away from the soil underneath the slab. Geothermal warmth is then captured and it not only prevents the frost heaves, but is also considerably more energy efficient since you no longer have to heat all of that cool air in the crawlspace. No risk of moisture issues. Overall, it considerably outperforms a crawlspace.

I feel much better now. I did ask and the engineer and he verified his house is on a FPSF and only in very rare circumstances (such as building on extreme slopes) would he use crawlspace or basements. It would appear the engineers are the experts and really know what they are talking about. I guess I got worked up trying do my own research on a subject I was unfamiliar with and reacted to anecdotal evidence from friends and unknown internet posters.

I hear there has been a lot of that going on since about March of 2020. Just substitute healthcare professionals for engineers.

 

[Jeffreauxdawg]

Well that's an interesting observation. Almost seems allegorical.

 

[greenbean.sixpack]

In most municipalities in the 'Sip, you'd be fine with no permit. I did a substantial addition in Rankin County about 10 years ago and no one ever said anything even when we sold it. In rural counties, like Carroll, absolutely no one would care, but if you did that in Madison, The City, Mary Hawkins would probably go in dry on you.

 

[wsjmsu75]

In most municipalities in the 'Sip, you'd be fine with no permit. I did a substantial addition in Rankin County about 10 years ago and no one ever said anything even when we sold it. In rural counties, like Carroll, absolutely no one would care, but if you did that in Madison, The City, Mary Hawkins would probably go in dry on you.

And if you live in one of these Madison subdivisions with a homeowners association and covenants, you better not even think about taking a piss without the HOA's permission.

 

[Mobile Bay]

I dunno man. Any idiot can be an engineer. I know this from experience because I am an idiot.

 

[xxxWalkTheDawg]

I believe they can refuse to allow you to buy utilities if you go rogue in Mississippi. That sucks.

Yep. My dad built a tractor shop and wired it for power and lights. The electrical service had schedule 80 grey conduit except for one coupling. He ran out of them and used a schedule 40 plumbing coupling in the conduit.

They wouldn’t hook up the power. I remember dad saying he would have sanded it and painted it grey if he thought it would have been a problem. Then it would have passed.