N/A slab vs crawlspace foundation for new construction

[FORANE]

We weren't looking but a lot in Gatlinburg was offered directly to us by the owners so we've bought another lot. We're planning on building another Airbnb cabin. We have both slab and crawlspace foundations currently in other properties and have had issues with millipedes in one with a crawlspace.

What foundation would you recommend? This build location is level so a slab would work.

 

[Daleandee]

Both can be advantageous for different reasons. If I had my druthers I'd go with a slab. Having said that the concern is that many, if not all, of the services (electrical, water, sewage) for the building are under that slab and that a problem means a lot more work to access them for repair.

I was in a slab home when the plumbing underneath began to leak. After tearing up the floor & slab, doing the repairs, and replacing the floor & carpet I wondered if the plumbing could be brought to the structure, brought up inside an exterior wall and all the plumbing ran through the attic. Insurance company said that not only would they not pay for such but wouldn't insure it either.

A crawlspace is a good option if you get a soil treatment and maintain it as well as insuring that nothing can get into that area. Ventilation is also of utmost importance. Paying someone to do any work that needs to be done in a crawlspace is a good way out but folks that do that tend to get paid quite handsomely.

 

[AV8R_87]

Having said that the concern is that many, if not all, of the services (electrical, water, sewage) for the building are under that slab and that a problem means a lot more work to access them for repair.

A friend had to deal with that isdue recently. Cost him 50k to replace corroded sewer lines under the slab.

That said... I hate crawlspaces.

My preference (not sure if per code/insurable/cost effective) would be to have the pipework in some sort of a trench in the slab, so you could still access it and inspect/repair it without demolishing the house.

 

[Stewartb]

Ask your GC. It’s very dependent on region, soils, etc.

Our AK house is crawlspace and TX is slab on grade. Wife hates the feel of the floor with the slab. Crawlspace is far more comfortable.

 

[FORANE]

I wonder if the cases of plumbing issues in slabs can be significantly associated with old metal pipe corroding. Some builders claim modern plumbing isn't likely to suffer these issues.

 

[Ed Haywood]

Slab may not be an option depending on frost line depth or lot slope. A local contractor will tell you quick which method works best in that area.

In Florida almost everything is slab.

 

[Stewartb]

In TX, plumbing is PEX and is run through the attic. If your ground dries out and the foundation cracks, in-floor plumbing can’t handle it. My first TX house had 36 engineered piers to stabilize the slab. That wasn’t cheap. The current house has monster grade beams and interior footings on 600yds of engineered compacted fill.

 

[Racerx]

Crawlspace with a slush coat.

 

[asicer]

Basement with a double wall convection loop thermal envelope, if you can swing it. Otherwise it’s going to depend on local conditions, particularly soil, climate, etc.

 

[AV8R_87]

Some builders claim modern plumbing isn't likely to suffer these issues.

And it won't be their problem to fix anyway.
That's what they said about cast iron piping in the 50s.

 

[asicer]

And it won't be their problem to fix anyway.
That's what they said about cast iron piping in the 50s.

“Not a problem at all” (until after I sell the business and retire to my cabin in the mountains)

 

[kyleb]

And it won't be their problem to fix anyway.
That's what they said about cast iron piping in the 50s.

Through at least the early 70's. Says the guy who spent Father's Day weekend repairing a section of ours (1971 house).

 

[asicer]

Says the guy who spent Father's Day weekend repairing a section of ours (1971 house).

Do you have aluminum wiring?

 

[kyleb]

Do you have aluminum wiring?

No. This was a very high end neighborhood when it was built. Custom homes, high end stuff. No aluminum wiring, none of that cheap-ass plastic sanitary drain pipe. ;-)

 

[flyingron]

I have two houses that are "slabs" in that they the lowest floor sits on the concrete with nothing but earth below. I don't have water lines there, just a few sewer connections for the drains on that level.

 

[Brad W]

I grew up in areas with both basements and crawl spaces, but have lived most of my adult life in FL slab homes.
Slabs are stupid (in my opinion)
I suppose it's cheaper so that's teh only advantage I can see.
If I were building and had a choice and money wasn't an issue...and a basement wasn't in the cards, I'd go with a crawl space. access for utilities, repairs, retrofits, storage... and I think houses look better up off the grade too!
I'd probably go with a finished in crawl space...I think they call it encapsulated or some such thing...basically a conditioned and on-grade basement, not underground. I'm not convinced that encapsulating a crawl space that was built to be vented and exposed is a good idea, but I think if it's designed and properly built it seems like it makes a lot of sense

 

[mark.staggs]

Agree that if you do crawlspace having it encapsulated would be better than a traditional unfinished. It prevents possible water intrusion and humidity under your flooring which can cause issues if you have traditional wood flooring.

We're currently building with a walk-out basement and slab floor down there, and there are only sewer lines in the slab. No water lines in the concrete so, in theory, fewer chances for super expensive leaks.

 

[GoFly]

He built on a slab with non pressure pipes in/under the slab, and pressure pipes and electrical in the ceiling.

 

[GaryM]

I'd favor crawlspace. Before we married, my wife had a home on slab. Pipe for the baseboard heat broke under the family room slab, leading to a month or two of insane water bills and heating bills before the problem was discovered. And then the real eye-watering costs kicked in for the repairs, ripping out a big chunk of slab, re-routing pipes, and making all the repairs.

 

[Brad W]

I grew up in areas with both basements and crawl spaces, but have lived most of my adult life in FL slab homes.
Slabs are stupid (in my opinion)
I suppose it's cheaper so that's teh only advantage I can see.
If I were building and had a choice and money wasn't an issue...and a basement wasn't in the cards, I'd go with a crawl space. access for utilities, repairs, retrofits, storage... and I think houses look better up off the grade too!
I'd probably go with a finished in crawl space...I think they call it encapsulated or some such thing...basically a conditioned and on-grade basement, not underground. I'm not convinced that encapsulating a crawl space that was built to be vented and exposed is a good idea, but I think if it's designed and properly built it seems like it makes a lot of sense

Agree that if you do crawlspace having it encapsulated would be better than a traditional unfinished. It prevents possible water intrusion and humidity under your flooring which can cause issues if you have traditional wood flooring.

I was thinking more about this, and remembering some research I did a while back for a building that we own that's about 110 years old. That one tends to be a bit damp in the crawl space and I recall quite some debate about encapsulating vs venting. In that case I decided that encapsulating makes a lot less good sense because it would be a constant battle to keep the moisture out.
I think where it makes better sense is with new construction, where you can control proper grading of the and around the structure and keep the crawl space safely high and dry without sump pumps
but
as I thought about it earlier today, if my new construction home was up on a nice high hill, high and dry, with proper grading, good soil, etc... then instead of sealing it in it might make better sense to leave it ventilated (in some climates anyway). I still think though that a slab floor in the crawl space with proper perimeter walls and very secure vents to securely keep the critters out would be nearly a must-have for me

 

[JeffinNV]

I've owned two homes with crawl spaces. If I were building a home it would have a deep crawl space, enough that I could walk hunched over to access the utilities as needed, instead of crawling.
I've seen slab homes built on grade and all I can think of is interior flooding in a heavy rain or spring breakup.

 

[kyleb]

I've owned two homes with crawl spaces. If I were building a home it would have a deep crawl space, enough that I could walk hunched over to access the utilities as needed, instead of crawling.
I've seen slab homes built on grade and all I can think of is interior flooding in a heavy rain or spring breakup.

My first home was that way. If you can't have a basement, I'd recommend a tall(ish) crawl space. My first home was plumbed with polybutylene lines on the supply side. I was able to replumb the entire thing (2 baths, kitchen, laundry) in a long day using crawl space access (single story home). It was a long day, but at the end of it, I had all copper supply lines and the water was flowing to all of the desired locations. Current house has 2 stories over a basement. I can work on anything on the first floor through the basement's drop ceiling. But the stuff under the basement slab? That gets expensive. I paid $5K about 15 years ago to have 50' of underground cast iron pipe lined with fiberglass/epoxy. Cheaper than tearing up the slab, but ouch.

 

[Paul Thomas]

There are TONS of STR homes for sale... is it worth building?

I prefer an encapsulated crawl space.

 

[FORANE]

There are TONS of STR homes for sale... is it worth building?

I prefer an encapsulated crawl space.

Fair question. As I mentioned, we weren't looking to buy a lot but it adjoins lot line with a couple other cabins we built, is in a great location and is a very good lot.

Some markets have pulled back, others less so. Perhaps that will change with time; in fact I expect it to, but at present our market in Gatlinburg is still expensive. The other aspect is our market does have a lot of STR but most on the market aren't the level of quality (and rental marketability) I will build.

 

[Albany Tom]

Around here, the only slab construction I remember seeing is commercial. Probably because they can plan the location for the bathrooms and they never change, and because a concrete floor with carpet is durable and cheap. The only houses I know of with crawl spaces, again in this area, are really low end. Along the lines of short term savings in having a foundation.

The only reason I wouldn't have a basement in a house is if when you dig deep enough you hit water, meaning you're in someplace like Florida. I like having a basement enough that I just wouldn't live in a place like that. But if you can go down a few feet, pour concrete and have a shallow crawl space I see that as very preferable to a slab. If you can put a moisture barrier below the concrete, and one way or another keep the humidity low in the crawl space, I think it would make the whole house better and more comfortable, and it makes maintaining the plumbing much easier and less expensive.

The other thing, probably more important than the above, is make sure the water drains away from the house. To me when someone says "location location location" it means "does the ground naturally slope away from the house?", because that's way more important than how far away you are from a movie theater or whatever.

 

[Clip4]

I think if I was considering a crawl space I would just do a basement.

 

[Craig]

Soil type and watertable depth should be a big part of your decisionmaking process. Where our primary home is, you will possibly hit rock before you are deep enough for a crawl space. On the otherhand, where our other place is, you would need to go to about 35 feet deep to set piers. The house built a few years ago, just down the street from out second place, took 30 piers for a 1200 square foot pier and beam foundation. Pier cost ended up being about 60% of thd total house cost. The owners were not happy about that., as the design had to be altered with updated engineering at least once that I know of.
EVerything in the west side of Houston is slab since the watertable averages about 2 feet bdlow the surface.

 

[FORANE]

We're in the mountains. My well next door is 700 feet deep.

 

[TCABM]

….We have both slab and crawlspace foundations currently in other properties and have had issues with millipedes in one with a crawlspace.

What foundation would you recommend? This build location is level so a slab would work.

If the cost is comparable, slab since your crawlspace cabin is causing a headache. With an STR as an investment, the other question is what’s more desirable when you go to offload the property.

 

[FORANE]

If the cost is comparable, slab since your crawlspace cabin is causing a headache. With an STR as an investment, the other question is what’s more desirable when you go to offload the property.

I will have to talk again with my builder, who's a decades old friend, regarding cost. He had suggested crawlspace for maintenance reasons when we briefly discussed it. I hadn't discussed the possibility of running plumbing supply lines outside of the foundation.
With regards to offloading, I suspect that will be after I'm gone. We've got a couple others I would sell first. Then with STR, the big factors in our area are gross income followed by aesthetics and location. I don't believe the typical buyer would place much weight on foundation type.

 

[pfarber]

A friend had to deal with that isdue recently. Cost him 50k to replace corroded sewer lines under the slab.

That said... I hate crawlspaces.

My preference (not sure if per code/insurable/cost effective) would be to have the pipework in some sort of a trench in the slab, so you could still access it and inspect/repair it without demolishing the house.

This is highly age and location dependent. I don't think I've ever lived in a post 2000's home that wasn't PVC sewer. My 1870's house in PA was mandated in the 1990's to hook up to public sewer and they required 4in PVC.

 

[TCABM]

I will have to talk again with my builder, who's a decades old friend, regarding cost. He had suggested crawlspace for maintenance reasons when we briefly discussed it.…

Other than six years split between Colorado and Italy, I’ve lived on nothing but slab all my life. In-slab utility maintenance has never been an issue in the houses I lived in; all constructed in 1973 or newer.

Some challenges I’ve seen with slabs is engineering for the soil. Expansive soil allows a monolithic slab to be stressed, leading to cracks which can be anything from cosmetic to structural. Site prep can help with much of that. The other big issue is settling. Most of that occurs in the first year or two and can result in drywall and/or stucco cracks. By law slabs in Texas have a 10-year structural warranty. A residential structural engineering firm would be the pros from Dover on foundations for your location.

… I hadn't discussed the possibility of running plumbing supply lines outside of the foundation.
….

Our current house runs most of our supply lines thru the attic and walls with returns in slab. The only in slab supply line I know of is to the kitchen island. The tap off the main is subgrade and in conduit where it pierces to foundation to feed the water heater and softener.

 

[FORANE]

I can't help but think of all those in floor radiant heat systems with pex running everywhere through the floor. Not that I have any intention of installing that but apparently some are comfortable with it.

No drywall or stucco. We're wood only.

 

[Rich Holt]

I am a big fan of crawlspaces, but I've mostly lived in the south, where insulating the floor is not that big of a deal. My current home has a crawl space that you can access on the way down to the basement.

 

[TCABM]

I can't help but think of all those in floor radiant heat systems with pex running everywhere through the floor. Not that I have any intention of installing that but apparently some are comfortable with it.

No drywall or stucco. We're wood only.View attachment 144966

I can't help but think of all those in floor radiant heat systems with pex running everywhere through the floor. Not that I have any intention of installing that but apparently some are comfortable with it.

No drywall or stucco. We're wood only.View attachment 144966

We had radiant heat in Colorado in the master bath, basement bath, and basement great room.

Awesome to wake up to warm tile on a sub-zero morning. We only turned the (fully finished walkout) basement great room on when we had company and planned to entertain down there in the winter. Usually took all day to have a measurable effect, but was a better option for us instead of putting a fireplace down there.

I don’t think I’d put it in an STR though.