HAWKEYE10
Member
We are thinking about having a new house built and I would like advice on the foundation. Slab or crawl space. All the houses I have lived in had a crawl space so I know nothing about a slab foundation. Don
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I don't know where you live, but if you have frost that goes into the ground in the winter you will have a foundation wall with a crawl space. Here in NW MT we have to have a 3ft. foundation wall below the surface of the ground. That is how deep frost can go here.
With a slab if frost goes deeper than the slab you can get all sorts of movement and cracks and plumbing breaking, etc. It all depends where you live. In humid climates sometimes a foundation wall is used for moisture from wicking through the slab.
So your environment will determine what you need.
John
With a slab if frost goes deeper than the slab you can get all sorts of movement and cracks and plumbing breaking, etc. It all depends where you live. In humid climates sometimes a foundation wall is used for moisture from wicking through the slab.
So your environment will determine what you need.
John
Crawler
Hawkeye
I think for TN, a crawl space would be best, if you are not adding a basement.
Good luck with your new home.
tb
Hawkeye
I think for TN, a crawl space would be best, if you are not adding a basement.
Good luck with your new home.
tb
wraco
Member
A slab on grade foundation requires the same minimum depth of excavation as a crawl. The depth of excavation for both types require the bottom of the footings to be supported by solid bearing ground and to be below the frost line. The frost line is determined by where you live with the development services department, of your local building inspection, setting the minimum depth.
I build houses here on the southern part of Vancouver Island where the local building code requires 18" of frost protection. This means the distance from the bottom of the footings to the backfill height must be a minimum of 18". Allowing for 8" of concrete foundation wall above the backfill height that translates into 2 foot concrete foundation walls bearing on 6" thick footings. The width of the footings is determined by the bearing capacity of the soil. (16" to 24" normally).
A slab on grade, as it's normally called, is when the interior of the foundation is backfilled with compacted free draining gravel or native free draining earth to height of 3 1/2" from the top of foundation. A 3 1/2" slab is poured and placed bringing the top of floor flush to the top of foundation.The plumbing and electrical service is placed in the compacted soil under the slab.
Usually a slab on grade is used for bsmt. entry homes where the living is above on a joist and plywood floor. A one level rancher on a slab is usually cheaper to build but walking and living on a slab can sometimes be uncomfortable unless in-floor-heating is installed.
A crawl space is more desireable for a one level home with a minimum, for access, in non-plumbing areas of 18", in plumbing areas and of 24" and a minumum of 36" if a force air furnance is installed in the crawl space. These crawl space heights are minimum requirements but if increased to 48", this area serves well for storage.
The crawl space exterior foundation walls are insulated with 2" rigid foam and the joist ends with R-20 fiberglass and sealed with a 6 mil poly vapor barrier.
There you have it.
Rod
I build houses here on the southern part of Vancouver Island where the local building code requires 18" of frost protection. This means the distance from the bottom of the footings to the backfill height must be a minimum of 18". Allowing for 8" of concrete foundation wall above the backfill height that translates into 2 foot concrete foundation walls bearing on 6" thick footings. The width of the footings is determined by the bearing capacity of the soil. (16" to 24" normally).
A slab on grade, as it's normally called, is when the interior of the foundation is backfilled with compacted free draining gravel or native free draining earth to height of 3 1/2" from the top of foundation. A 3 1/2" slab is poured and placed bringing the top of floor flush to the top of foundation.The plumbing and electrical service is placed in the compacted soil under the slab.
Usually a slab on grade is used for bsmt. entry homes where the living is above on a joist and plywood floor. A one level rancher on a slab is usually cheaper to build but walking and living on a slab can sometimes be uncomfortable unless in-floor-heating is installed.
A crawl space is more desireable for a one level home with a minimum, for access, in non-plumbing areas of 18", in plumbing areas and of 24" and a minumum of 36" if a force air furnance is installed in the crawl space. These crawl space heights are minimum requirements but if increased to 48", this area serves well for storage.
The crawl space exterior foundation walls are insulated with 2" rigid foam and the joist ends with R-20 fiberglass and sealed with a 6 mil poly vapor barrier.
There you have it.
Rod
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I'd rank them basement (best), crawl space, slab (worst)
obviously, the relative cost would be the inverse.
If nothing else, a crawlspace or basement makes getting to the plumbing and electrical much easier. My last 2 places have been hybrids with mostly a basement, but crawl space(s) under all or part of addition(s). I hate fighting with those crawl spaces when I need to work on something under those areas, but at least I don't have to rip up my floor and break out a jack-hammer.
ps. don't forget a built in safe of some sort.
obviously, the relative cost would be the inverse.
If nothing else, a crawlspace or basement makes getting to the plumbing and electrical much easier. My last 2 places have been hybrids with mostly a basement, but crawl space(s) under all or part of addition(s). I hate fighting with those crawl spaces when I need to work on something under those areas, but at least I don't have to rip up my floor and break out a jack-hammer.
ps. don't forget a built in safe of some sort.
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Slab is the worst choice. My brother wants to remodel his kitchen, but since he's on a slab the cost of relocating the gas stove is horrendous. The gas line is buried in the slab. A crawl space makes utilities (especially plumbing) MUCH easier. Just make sure that if you have a crawl space that you have a good solid floor structure. Don't skimp. You don't want the floor to sag.
OP
HAWKEYE10
Member
Thanks guys I think I will be sure and go with the crawl space. I don't think in Tennessee you would have to worry about the frost line but if down the road we had pluming problems or wanted to remodel there would be a problem with a slab. Don
Its easy to put in extra pillars in a crawl space, just don't get too carried away.
I think you need to look at the long term to best suit your needs. If you are set on a crawl space you will need footers all around and where the home is supported through out. I would have the walls poured not block and pour a minimum of 2" slab through out the crawl space. Many people come back and do this later at a higher cost.
For me I prefer a poured wall basement. We live in a area where tornado can happen from time to time. The basement is just some piece of mind and provides us with much more room for whatever. My basement is totally underground with no outside door. It does have 2 windows 5' off the floor if you needed to get out.
Just think of your needs, and long term as well. Find out what the codes are and follow them. I have been at many many homes to pour concrete and they are fixing things to pass inspection. You don't want a bunch of trucks and people on your job, and fail inspection. You will have to send those trucks back and pay of the concrete at a cost of $1000 per load.
For me I prefer a poured wall basement. We live in a area where tornado can happen from time to time. The basement is just some piece of mind and provides us with much more room for whatever. My basement is totally underground with no outside door. It does have 2 windows 5' off the floor if you needed to get out.
Just think of your needs, and long term as well. Find out what the codes are and follow them. I have been at many many homes to pour concrete and they are fixing things to pass inspection. You don't want a bunch of trucks and people on your job, and fail inspection. You will have to send those trucks back and pay of the concrete at a cost of $1000 per load.
I do not know what’s normal in your area, but unless you’re on slab rock I would want a basement under as much of the house as possible. (much better resale in my area) Storage, utility room, storage, work shop/ gun room and O did I mention storage? Yes it raises the cost but the tradeoffs are worth it.
Basements are like garages you can never have one big enough. This house has a full 10’ deep basement under ½ of the house with the other ½ being a 30x30 garage. My previous house had a basement under the main house with a crawl space under the 20x20 addition. Big mistake I never should have done a crawlspace, it’s just wasted area.
That’s just my thoughts do what is best for you!
Basements are like garages you can never have one big enough. This house has a full 10’ deep basement under ½ of the house with the other ½ being a 30x30 garage. My previous house had a basement under the main house with a crawl space under the 20x20 addition. Big mistake I never should have done a crawlspace, it’s just wasted area.
That’s just my thoughts do what is best for you!
jag312
Member
Just curious; do the building codes in Tennessee require the house to be bolted to the foundation? It is required in California because of the earthquakes. When the New Madrid Fault goes again, houses not bolted down will slip off the foundation.
What is the standard building method in your area??? If they have basements I sure would love to have one of those again!. Great place for "stuff"
Here we have no basements or attics to speak of.
Folks claim that slab is worst but here in S Florida it is pretty much the only kind. The only variable is if it is a monolithic or a floating (block perimeter) slab.
Here we have no basements or attics to speak of.Folks claim that slab is worst but here in S Florida it is pretty much the only kind. The only variable is if it is a monolithic or a floating (block perimeter) slab.
BigBill
Absent Comrade
Here it matters how deep the under ground water is if we hit it when we do the test bores. If the water level is too high we do a slab foundation thats 12" above the ground level. If we do a foundation with a cellar we coat the outside walls with tar, add drain pipe and gravel all the way around the foundation for drainage at the footings. At the sametime we do the under ground piping for the roof gutters and leaders to steer the roof drainage away from the foundation/house. This keeps the cellar dry plus if we have a slab foundation it won't frost heave.
Today in the floor in a cellar we put down 1" foam with clear plastic on top of it before we pour the floor. This makes the floor warmer and keeps out the moisture. My 48' x 28' garage was toasty warm with the floor insulated with the walls and ceiling when i lit the woodstove. I used a top loader wood stove raised up so the 4" of gas fumes if any couldn't be a dannger.
Today in the floor in a cellar we put down 1" foam with clear plastic on top of it before we pour the floor. This makes the floor warmer and keeps out the moisture. My 48' x 28' garage was toasty warm with the floor insulated with the walls and ceiling when i lit the woodstove. I used a top loader wood stove raised up so the 4" of gas fumes if any couldn't be a dannger.
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williamlayton
Member
There is not much choice here on the Gulf Coast of Texas. Water table is so high a basement would cause the house to float---like a swimming pool without water does.
Crawl spaces are not reccommended for a lot of reasons.
Post and beam is not good because the soil moves too much.
Slab on grade with GOOD wide and deep footing and sand as a fill to the slab bottom.
Still---here in Texas---the slab repair boys make good money.
Blessings
Crawl spaces are not reccommended for a lot of reasons.
Post and beam is not good because the soil moves too much.
Slab on grade with GOOD wide and deep footing and sand as a fill to the slab bottom.
Still---here in Texas---the slab repair boys make good money.
Blessings
Farmer17
Member
I build houses in Oklahoma and around here I would bet 99% of new homes are slab on grade. Concrete piers under the footing are really pretty cheap and I have never had any foundation problems with any of my houses. HVAC and elec is in the attic and the only thing under ground is plumbing. With a crawl space you have more stem wall expense and exterior fascade and if the fascade is brick or rock that can be expensive. if the fascade is siding its not too much money though. You also have to have the expense of steps to get in and out and old folks or wheel chairs have more of an issue. People say slab on grade is colder in the winter time but that really is a not a problem around here.
627 city hunter
Member
Do you need an senior architecture student to do some drawings, HAWKEYE10?
Black_Sheep
Member
I would do a basement if it will fit your budget. The incremental cost vs a slabbed crawl space will be minimal and you will gain a lot of room.
A basement is the most useful and the most expensive,but is fairly cheap additional floorspace.A slab is cheap,but has nothing else going for it and they make damned uncomfortable floors,even with pad and carpet.A crawlspace is a good compromise.
jaykellogg
Absent Comrade
I built a small house in Western North Carolina two years ago and it is on a crawlspace. There is 6mil poly down there and there is room enough to store things there. There is even room in one corner to have a workbench. I would go with the crawlspace unless your contractor tells you a slab is absolutely necessary. I stucco'd my crawlspace blocks.
Regarding a poured foundation as someone recommended, I believe you will find it costs much more unless there are a couple of good sub contractors to do the work. i have had both and I really don't think i'd pay any extra for poured. Block actually is stronger than poured. If you want an extra strong wall, speak to the contractor. Depending on the code in your area they may require reinforcing every three courses, or none at all. You could reinforce every course. Also you may have to put rebar in some cells and pour them full of concrete. Again, you could increase that. If your code does not require bolting the house to the foundation, I would anyway. Good Luck!
Regarding a poured foundation as someone recommended, I believe you will find it costs much more unless there are a couple of good sub contractors to do the work. i have had both and I really don't think i'd pay any extra for poured. Block actually is stronger than poured. If you want an extra strong wall, speak to the contractor. Depending on the code in your area they may require reinforcing every three courses, or none at all. You could reinforce every course. Also you may have to put rebar in some cells and pour them full of concrete. Again, you could increase that. If your code does not require bolting the house to the foundation, I would anyway. Good Luck!
