crawl space or slab

[Mcompton1973]

first....i have read some other similar post and everyone says basement. I need answer to crawl space vs slab. I am in Oklahoma. ground is too rocky for a basement, and cost difference too high.

I am building a pretty small house. maybe 800-900sq ft. Simple rectangle with porches/decks on front and back. Land slopes some...short side of rectangle will drop 2 feet roughly.

My plan is to have someone basically build me a shell of a house. Maybe 20x45 or 25x35 rectangle or something. Then I can finish it out myself over time. The goal is to have a house and no mortgage eventually. Becaue of the slope of the land I am leaning to crawl space. I also feel like crawl space is more forgiving. (i.e. I can move a bathroom if needed in the future.) Slab would seem to me very cold in the winter...but I dont know, maybe you can insulate??? Cost is a big factor. Which is cheeper? does that change if I do a lot of the work on crawl space? To me slab seems less owner builder friendly....but maybe I co do that also?

[Alice In TX/MO]

Yes, crawl space allows you to work on plumbing, level the house when necessary, etc. Crawl spaces contribute to cold in the winter because you have to allow air flow through it or moisture builds up, and your floor joists rot. Don't ask how I know.

Our house is on a slab, and we spent $20,000 getting it leveled after the doors quit closing and cracks appeared in the walls. Will NEVER build on a slab again.

[jwal10]

IF you put in floor heat, slab for sure. Otherwise I like crawlspace. Footer and stem wall, 1 row of post and beam down middle of narrow side. Silent floor I-beam for floor, dropped, top even with top of treated plate. Fill full void of floor joist with fiberglass batts. 3/4" tonque and groove plywood glued and nailed. Single plate on top of floor, 2"x6"studs, double top plate. Wrap studs with house wrap, no groove T-111 siding. Spray on 2" of foam to seal and 3 1/2" fiberglass batts in walls. 18" blow in above ceiling. 1/2" plywood over trusses, heavy felt, standing seam roof....James

[Steve_S]

Crawlspaces have some advantages and some disadvantages and there is a great deal of information on the web from credible sources that discuss the differences. I have personally had the same debate and spent a lot of time researching variations and made the decision to go with a Frost Protected Shallow Foundation with gravel fill...

In the earlier days before FPSF was fully developed and understood, many contractors used sand under the slab without a foam layer to insulate and without a moisture barrier. This resulted in heaving, cracks & shifting. In floor heating systems can be very efficient and most comfortable if done properly and again, this technology / method has vastly improved over the past decade and is quite mature now.

With regards to your climate zone, I am in North Eastern Ontario Canada, which as I'm sure you can appreciate, it can get very very cold and FPSF is now widely used here for many reasons. It is considerably more cost effective than some of the alternatives and provides a solid base to build on.

Here is a good PDF document regarding FPSF foundations http://publications.gc.ca/collection...7-1998-eng.pdf This is on a Canadian Government site.

One thing I should point out which may not be as obvious as it should. A homeowner can do much more work in regards to prepping for FPSF foundation... You can do the excavation, packing, gravel work, laying out foam & plastic sheeting, setting the forms up, laying out the REBAR & Mesh wire, in-floor heating lines... and depending on slab size, you could even mix up your own concrete (not really something you want to do, it's a major PITA). This all equates to big dollar savings !

Depending on your area and availability, you may be able to get a concrete company that does "Mobile Mixing". Mobile Concrete mixers, mix the product on-site and will only charge customers for what they actually use. This prevents over ordering the amount of concrete required and more importantly prevents under-ordering which is the worst problem when pouring your slab. You can finish the concrete floor to your liking, colour it, finish & polish it and even embed various aggregates to create a unique & custom look. I've even seen it done in a way to make it appear like a marbleized finish with coloured veining and patterns. Google "marbleized concrete finish" and look at the images that pop up and some articles to give you a better idea of what I mentioned.

Hope it helps give you some extra ideas and thoughts for your project.
Steve

[TnAndy]

I built quite a few houses over the years. Slab always worked out cheaper. IF done correctly you should not have a problem.

As far as things like plumbing...yes, you do have to plan it out.....but then, you do in a concrete basement floor too. And if you really really really want to make changes later (i did), then they rent concrete saws at the rental place:





My own house is a combination of full basement under half of it, and slab on the rest of it (hit rock, could not afford to have it removed at that point in life). We had to build up about 5' on one outside wall, then fill. Insulated it well, and been quite happy with the results for many years. One thing about it, you can have a flaming log roll out of the fireplace and it won't burn the house down ! ( sorta hard on the finish floor though )

[Rustaholic]

I hate the permanence of a slab of concrete.
If a basement is not an option I would do a crawl space every time.
Just what you wrote.
It is so easy to move or add plumbing.
Here in my area of Michigan we put water heaters and horizontal furnaces in crawl spaces.
That keeps them out of your living area.

[Gray Wolf]

We've done both.

Pipes don't freeze with slab. Run all supply lines in the interior walls (nothing in the exterior walls if it freezes hard where you are) and all you'll have in the floor are drains.

Crawl space---Dig down or build pony-walls so that you get to 3'-4' headroom in crawl space. Much easier to work in if you have plumbing or wiring you want to access. It also jacks the house up a bit which IMO, makes for a better looking house and has some security benifits if it is 6'+ to the bottom of the windows.

[nosedirt]

I have 25 plus years in the construction business. If you are not doing a basement, I would do a slab. If you do proper planning, you don't need to move plumbing. Crawl spaces, no matter how well built and ventilated are damp. That dampness affects the floor joists, your health, and many other things. Gray Wolf is correct about not having to worry about freezing pipes. I lived in OK for four years and that is definitely a thing to think about. You will have to close the vents every fall, cover and insulate. Then when you uncover them in the spring, you will be amazed at the amount of moisture build up.
Snakes love crawlspaces. Especially in Oklahoma. Steve S is pointing you in the right direction. And you can save a lot if you follow his suggestions. A properly designed and poured slab will not heave and crack.
Did I mention snakes and spiders love crawlspaces. If there is anyone in your family with allergies or any type of sinus or lung issues, crawlspace is a no no.

ND

[gila_dog]

We've built 3 houses. The first on a simple slab. It was cold and hard. The 2nd on a slab with radiant heating. The floor was hard and the heating system was complex and expensive to build and expensive to operate. The 3rd is has a crawl space. The floor is built of engineered joists, 3/4" plywood, Hardi backer, then ceramic tile. Between the joists, from below, are 8" fiberglass batts. This floor is softer and warmer than the slab floors. The foundation is stem walls made of concrete filled cinder blocks and concrete piers in the middle. Probably more expensive to build than a simple unheated slab, but much more comfortable. Also the crawl space (2 to 3' high) give us some room for storage and also elevates the house and gives it some flood protection. The insulated tile floor also provides some thermal mass (insulated interior mass) so that the passive solar heating provided by the south facing windows works really well. That thermal mass also moderates the temperature in the house when we use the wood stove. And it also makes the house easier to cool in the summer. With a crawl space, tho, one must make sure it's well protected from vermin getting in. That isn't hard tho. The stem wall is only penetrated by vents around the perimeter, which have metal grill covers. We don't have to worry about moisture in the crawl space because we live in a pretty arid place. But I can see how in a wet place the ground under the house could get moist.

[Dave S.]

I would go slab over crawl space. If your house needs levelling at point, then something was seriously screwed up during construction. Around here, you have to do a frost wall. It really isn't much more to go full basement at that point.

[AmericanStand]

Whats the point of spending 3/4 of the money to have a basement and winding up with something you cant use?
Ive seen a house with the basement cut into solid rock, Ive seen a waterfront house with two of the basement walls in contact with the water.
Ive never seen reason for a crawl space. If you really want to collect skunks ,snakes and spiders that bad set a trap in the woods!

[ET1 SS]

It is hard to stop a heated slab from wicking heat into the ground.

I would go with a crawl-space, and a heated floor.

[Ozarks Tom]

Not knowing where in OK you are, all I can tell you is North Texas "black gumbo" soil will shrink and expand with moisture levels, causing havoc with a slab. Leveling is expensive, cost us $12,000 just to get a house sellable. Even post-tension slabs will crack over that stuff.

[Gray Wolf]

Building codes require insulation under the slab. You can always put in more. Our slab has 4" of foam and seems to hold heat pretty well.

[nosedirt]

Not all slabs are the same. Post tension gets a lot of press but my professional opinion says I would not waste my time with one. Regardless of slab or crawl space, you need to do have a soil test anyway for the engineer to sign off on the design to get your permit. Even if no permit is required, it is well worth the effort. The foundation is extremely important. But with that aside, I believe Steve S gave you some good advice. If not that route then i would go with a RAFT slab. I am currently in a home I built 10 years ago on very unstable soil. I did a 14" RAFT. The bottom floor including garage is around 1800 square feet. I recently stripped all the floors and laid down wood. I did not find one crack, not even hairline. Of course I don't have the freeze thaw to same extent of OK so you would need to modify according to engineer's recommendations.

Myself, I would do a basement in Oklahoma, even with the issue of rock. But that was not the question you asked so I will stick to the question of slab or crawl.

[nosedirt]

Someone mentioned doing crawlspace in case of flooding. Why would you build a new home where this is a concern? Stay out of the flood plain and grade properly and flooding is not an issue.

[mnn2501]

Everyone I know in TX with a slab eventually has to have them leveled.
Do Pier and Beam instead.

[Alaska]

Im a crawl space/ basement kinda guy. with a slab there is plumbing and electrical in the concrete its not if its when that has to be dealt with.
And I like change much easier with a crawlspace/basement.

[Declan]

I have a crawl space. It is lined with a heavy duty vapor barrier. I haven't had any real problems since I bought the house other than some crickets that were easily gotten rid of when I first moved in. When it was down in the single digits and around zero, my heat didn't really come on any more and my house was not cold. My crawl space vents have fine wire mesh over them and are otherwise open 24/7/365 and none of my pipes froze. My heat/AC units were under there but when I had a new one put in I had them put the filters on the outside so I would not have to crawl up under the house once a month. I went with the bio filter that only has to be changed twice a year. There were even racks under there where a prior owner used to keep his potatoes.

I have no experience with slab foundations.

[GoldenCityMuse]

If a slab is done right. That is a big IF. Very , very few are done right. My dad's house has had 2 leaks in the slab due to cracked water sypply pipes. Both times required breaking the tile, sawing out the slab, and making the repair.

Even a 6' basement will make good storage in the hot OK summers.