Slab Construction?

[Alan L.]

Slab on grade costs alot less than crawl space (pier and beam). Back in 2006 my slab including forms, labor, concrete, everything turnkey was $3.90 per square foot. Crawl space would be at least double that, probably more than double. Then you have to worry about hanging the pipes and protecting them from freezing, and keeping varmints out of there. With all of that I'd rather have the crawl space, but just cost too much. I like that idea that you could run new lines if needed.

 

[ultrarunner]

Brother's home is in a neighborhood dating around 1950 and just about everyone has had slab copper water line problems.

When we did his remodel I ran all new copper in the ceiling... that was 12 years ago.

His is the only house in the family with no crawl space...

 

[dave1949]

In northern areas a crawlspace wall needs to be 4' deep to get below the frost depth. That's already half the height of a basement wall, so most people do a full basement with a slab floor poured inside the foundation wall footer rather than a crawlspace. For usefulness, a basement is 1000 times better than a crawlspace as long as it is a dry basement.

If it is a high water table area with no gravity drain possible, I would think very carefully about a full basement. A wet basement can become more trouble than it's worth and I wouldn't plan on using wet area basements as finished living space. The odds are that you will get water damage sometime or other in spite of having a sump pump. Furnaces, water heaters and washer-dryers don't look good sitting in a foot of water.

 

[vtsnowedin]

Yes it is a regional thing. I use a computer program to appraise houses for the town. The cost figures in it come from Marshall and Swift. Their national average for a house assumes a crawl space. It deducts for slabs and adds on for basements and finished basements. Floor drains are pretty standard in all three but not in swampy areas where they might work backwards on the owner.
I had my walkout basement blasted out of solid rock just out of Vermonter stubbornness. If the house was to burn I could have the basement capped over and live in the basement in a week or so as all the plumbing I need is there.
But back to the OP. "If it aint broke don't fix it.”

 

[dave1949]

I wonder what the reasoning is for deducting for a slab? That seems like out of date thinking for newer construction. I suppose for valuation purposes, a slab is a slab, as if they were all created equal.

I know back in the 1980's, some poor slabs were put in in S. Maine. That gave slabs a bad name and used home buyers tended to shy away from them. The market value of those homes definitely takes a hit.

If a slab is done correctly there is more planning, work and material involved than those builders of the 80's realized, but there is nothing inherently wrong with them. To build a good passive solar home, having a slab on grade is very useful.

 

[deepNdirt]

Houses being built on slabs are for quit often done to save time, (Production Home's) I worked 16 years for one of the largest "Production Home" Builders here in Ga, when I first started with them Their goal was to get the homeowners in their homes within 90 days of the signing of contract, when other production builders started their businesses up the company I worked for decided to pickup production in attempt to corner the market and started promising to have homeowners in their home within 60 days,
Of course quality dropped off as production increased, the company just higher ed on more Warranty and QA people,
At this point I was allowed 2 days to trim-out and average 2500 sq.ft home, ( standard trim packages ) 3 days for Deluxe trim,
The last year I worked for them they had once again increase production and dropped the time to only 30 days,
and I now had 1 day to trim-out the same sq. ft. houses, Deluxe trim included, There were a few times when I would trim 2 houses a day just to keep up, BTW the framers have 3 days, but I've seen them build 2 story houses in 2 days,
I'm sorry I got off subject,
But what I'm saying is..... most of the houses built on slabs are built to save time and money,

 

[vtsnowedin]

I wonder what the reasoning is for deducting for a slab? .

It is cheaper to build then the other options so adds less value to the completed house. The Crawl space includes short walls and footings below frost line and raises the sills above ground level which makes the house more durable when considering moisture, termites and surface drainage. A full basement adds useful living or storage space and frees up space upstairs that otherwise would hold heating and hot water equipment. To me a full basement under a smaller house is the most economical way to go in the long term even if it cost more initially.

 

[EddieWalker]

I prefer a concrete slab foundation over pier and beam. I've never lived where they have basements, and I don't have any experience with basements, so I can't comment on that. I also wont get into the pros and cons over one or the other on new construction. What I will say is that if the slab is in good shape, then there shouldn't be anything to worry about. The concern with a slab foundation is movement in the soil that results in cracking of the slab. This is impossible to fix, and very expensive to minimize. Usually the repairs last a few years and then it starts all over again. You need to do a very detailed inspection of the flooring and sheetrock. Cracks in the sheetrock can be from a poor roof design, or somebody cutting away supporting lumber in the roof for plumbing or AC ducts, so don't assume sheetrock cracks are foundation related. Be sure to look all around the exterior of the slab. It should be exposed. If it's covered in dirt, remove the dirt and look. This is also the number one way termites get into the walls, so if there is dirt covering the slab, it needs to be removed anyway. If the slab is bad, you will see it there. Then you need to decide if you want to deal with that money pit or move on.

As for the plumbing going through the slab, if everything is still working after all these years, you should be fine. I like houses built in the 70's. They are usually ugly, but the wood and materials used are all heavy duty, high quality. In the 80's, the EPA took over and made everything a mess with new regulations that gave us pressboard, plastic and glue that never held. Just try removing the wallpaper on a house from the 70's compared to one in the 80's. That glue they used back then is permanent!!! In the 90's things started getting better as manufacturers stared to standardize things and quality improved.

If you do have a leak under the slab, it's pretty easy to cut it out with a diamond blade saw and SDS Max rotary hammer. I do this all the time when remodeling a house. It's a mess, and you need to redo the flooring, but pretty straight forward with the right tools. Finding the leak is where it gets interesting. On some of the jobs I've done, instead of cutting open the floor trying to find it, I just cap the line, then run PEX up the wall, through the attic and down the wall where it needs to be. This is usually a day job, plus repairing the walls, or replacing what was in front of the wall.

Eddie

 

[JimRB]

I have a full bathroom in my walk in slab basement. My septic tank is jut outside the basement door. All the waste is plumbed through and under the slab. The supplies are in wood walls and such. Lots of slab house in Georgia with no issues. My house has plain old white PVC from the pump to the house.

I had to install a calcite filter to bump up the PH in my water as the water was too acidic and was eating up my copper.

I assume but I could very well be wrong that smurf supply lines from the water meter or well stop just outside the house. Smurf pipe under a slab would be a disaster. For those of you who have not seen or heard smurf pipe was a blue water supply line popular in the 1980's that breaks 10-20 years later. I thought I read they used no UV inhibitors so the stuff started to degrade while sitting waiting to be buried. Could have been some other reason for failure. In any event in Georgia there were/are plenty of blue water supply lines waiting to fail.

I worked for a high production builder for I think 3 months. That might have been to worst job I ever had in my life. Stupid mistakes done by architects and subcontractors made for some ridiculous messes in new occupied houses. Shower pans that leaked, blue board for tile backer in showers, copper water pipes in garages with conditioned space and bathrooms above (read this as frozen and broken water pipes due to poor insulation practices.) It is a bit hard to build a quality house when on tight time frame, underpaid subs, poor Q&A, fistfights between superintendents and subs (not me, I get hurt when boxing), people who do not speak the same language (even if everyone is speaking English). Actually a tight time frame is ok, Ridiculous time frame of a month or two is too tight for most subs I would guess.

 

[Egon]

Slab/Basement : either work well if constructed properly.