We are house hunting in Vermont. We recently came upon a nicely appointed 2 year old modular home that was built on a slab. Although the house is beautifully done on the inside (radiant heat throughout) , I am concerned about the stability of a slab foundation in an area that has severe winters. The piece of property that the home is located on is flat but I did notice that some areas of the yard were a bit wet (no recent heavy rains either). Also, I was wondering if adding on or knocking down walls for expansion, would pose a problem in the future due to the lack of a foundation. Any insight would be appreciated!
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Well you have the advantage, being a modular, that will the slab fails in a few years that you can just lift off the house and put in a real foundation.
But are you sure that it does not have anything other than a slab.
It could be a shallow frost protected foundation system or pier and ground beam system.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks for your feedback. I'm looking into your question re: frost barrier and/or post/beam. Do you know anything about adding on to a modular home? Is it any different than a regular addition?
I know that there are all kinds of modular homes. Some mutliple story and multiple wings.But the only hands on experience that I have had with one is a more conviential style. It was fairly large, 24x70-70. Two section jointed in the middle.The exterior walls where 2x6. I think that the marriage wall was 2x3's on each half.In this particular one the interior finish was REAL CHEAP. The walls, which we where paint was 3/8 DW with a vinyl covering and modeling strips to cover the joints. And all of the molding at the doors and the cabinets was all a "paper covered" mdf. And even using special "special surface" masking tape caused problems.However, when we where there one of the neigbhors stopped by and mentioned that the neighbor had an option for conventional DW. And possibly a cabinet/trim upgrade.All of that said. I have have limited knowledge of the construction, but garage was an addon. It might have been a kit or even premade, but it setup on a slab separate from the house and there was a step down.So I don't see any reasons that you could not addon to that building..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Very interesting.
In theory if the slab is strong enough and the drainage is good enough, there shouldn't be any problem. But in real life I haven't seen a house trying to test that theory.
Thanks. I had read somewhere that slabs could have the potential to buckle and that if you had plumbing issues it would be hard to access the pipes. What do you think the likelihood of buckling is? Also, what do you think about the plumbing concerns? Any thoughts?
"What do you think the likelihood of buckling is?"There is no way to know that from here.18" of compacted, well drained mineral base is needed as a general rule.
If the builder cut corners and poured the slab on softer soil or did not do good drainage details, then the bearing soil will move and let things settle more where the load is heaviest. It is less a matter of the floor buckling up than the slab settling down more in some places than others.To know, you would need to have a core sampled of the soil to see if there is foam insulation and to see how deep the mineral base is.
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In real life I have done several and live in one.
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Around here, people are too conservative and stubborn to upset the status quo, besides we need the basement to store all the junks.
Edited 9/27/2007 1:23 am ET by TomC
No matter how deep the foundation, the soils beneath must provide adequate bearing. It doesn't matter how wet the yard is, it's the drainage beneath the slab that's important. Too wet, and bearing suffers..... maybe, depending on the soil classification.
The foundation and soils beneath it must be kept from freezing unless those soils are truly non-frost susceptible. That is... they won't expand when frozen. The foundation and the soils beneath can be kept from freezing by perimeter insulation. This is easily accomplished on a deep foundation but is still very possible on a shallow foundation.
The house in question probably has a shallow perimeter foundation (and possibly some interior footers depending on loads) and is not simply a slab. The radiant heat wouldn't be worth a hoot if the foundation wasn't insulated at all. If the slab is insulated without perimeter insulation then a thaw bulb that encompases the perimeter foundation won't properly develop.
I would have a licensed civil engineer look at this house prior to purchase.
Greatly appreciate your comments. If you were buying a home would you stay away from a slab?
No I wouldn't necessarily stay away from a slab. I'd be cautious though. I think Piffen has addressed most of the issues.
It is a well established practice to build on monoslab in cold climates when using the principles of the FPSF ( google it - Frost Protected Shallow Foundation)
The problem is verifying whether it was built that way, or if drainage, compaction, and insulation details were put in place or not.
An addition can be done if carefull not to interrupt and damage existing underlying soils drainage
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Could he auger into the ground about 3' from building and see if the auger kicks up blue/pink polystyrene? If so, it is probably a FPSF, no?
Right, but I would try it just under two feet away. I would be looking for the foam and for the type of soils underlying it
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