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Anyone bought a house or condo on a concrete slab?

By skinnyninja follow skinnyninja   2012 Aug 6, 1:47pm 8,038 views   10 comments   watch   nsfw   quote   share    


Just curious, my parents are looking at condos in the area (Michigan) and they are wondering if anyone here has ever bought a house or a condo that was on a concrete slab.

They are looking at resale condos around the 200K to 300K range. A few of them are built on concrete slabs and they are wondering if they can get some feedback on them first....

Any help is much appreciated! Thanks!

1   bmwman91   ignore (1)   2012 Aug 6, 3:30pm     ↓ dislike (0)   quote   flag        

What exactly are they interested in knowing about them?

I lived in a very large, relatively high end apartment complex (basically condos) for a few years, and it had slab foundations. They had cracked here & there, and I could easily feel the cracks through the pad/carpet. On top of that, a study done here found greatly increased incidence of Alzheimer's in people that had lived in houses with slab foundations in this area for 40+ years due to the large number of semiconductor fab Super Fund sites (areas where hazardous chemical waste had leeched into the ground due to the chip industry). I would advise them to research the history of the area that they are looking in for information on former industry there and if there are known toxic dumping grounds or Super Fund sites (if called that over there).

2   E-man   ignore (0)   2012 Aug 6, 3:56pm     ↓ dislike (0)   quote   flag        

To add to what BMWman said, how old is the condo? How thick is the concrete slab if you could tell? What is the type of soil at the site? Adobe clay, silty loam, sand, gravel? What do they want to know about slab foundation? Its performance compared to other type of foundation? How many stories is this condo?

3   skinnyninja   ignore (0)   2012 Aug 7, 3:18am     ↓ dislike (0)   quote   flag        

OK thank you for the input so far.

To clarify a bit:

Their basic question is: basement or slab?

They know that the slabs get cracked at times, how big a problem is that?

They also know that sometimes plumbing is integrated into a slab, can that create problems?

They are not sure on the thickness of the slabs or of the soil type, but they are checking into it.

They are also wondering about ergonomics of a slab, is it worse if you have a bad back, etc?

Also wondering if there are major differences in utilities with slab vs. basement, heating, etc.?

Thanks again for any input, my folks are most appreciative of this forum!

4   tts   ignore (0)   2012 Aug 7, 1:40pm     ↓ dislike (0)   quote   flag        

skinnyninja says

Their basic question is: basement or slab?

Both have their up and downsides. It really depends on their wants/needs if they should get a house with a basement. Sometimes you can add a basement later, sometimes you can't depending on local building codes and other factors like the depth of the water table.
skinnyninja says

They know that the slabs get cracked at times, how big a problem is that?

Concrete always does 2 things: 1) get hard, 2) crack.

Nearly all homes built in the last few decades use concrete for the basement walls and/or concrete blocks. So there is no avoiding the cracking issue irregardless of wether you have a slab or basement.

That being said so long as the cracks aren't big you don't have much to worry about as some cracking is normal and expected AND designed for when the plans were made. If worried about this talk to a inspector for more information and have him look at any cracks.
skinnyninja says

They also know that sometimes plumbing is integrated into a slab, can that create problems?

If its very old (ie. 60 yr +) or installed improperly sure it can be a real PITA to fix. Otherwise there isn't anything to worry about.
skinnyninja says

They are not sure on the thickness of the slabs or of the soil type, but they are checking into it.

Slab thickness should follow code for foundations. They have to talk with a local permit guy to find that out but its almost always 3-4" thick at a minimum for the inside portion, the edges will constitute the footing and so will be much thicker. How much thicker varies considerably depending on where the frost line is in your area. Look at the plans or talk to the permit guy or a inspector to find out.
skinnyninja says

They are also wondering about ergonomics of a slab, is it worse if you have a bad back, etc?

I suppose if you don't put down a pad and carpet sure. Otherwise I never heard of a ergonomic issue with concrete flooring/slab.
skinnyninja says

Also wondering if there are major differences in utilities with slab vs. basement, heating, etc.?

Can be. Reaaaally depends on local weather/soil conditions. I've lived in homes that got flooded in the basement every year so a sump pump was required but there were still mold and concrete degradation issues.

FWIW a home with a crawl space of some sort is generally considered the best compromise between a slab foundation and a basement. You can still access plumbing and wiring but it avoids any long term issues that a basement might have.

Most homes these days use a slab foundation though since its cheap and fast. The ones made in the last few years are starting to insulate the footing too BTW which does make a nice improvement in heating/cooling efficiency. They're also using PEX tubing wrapped in card board or plastic as well for plumbing when they put them in now as well.

I wouldn't worry about a slab home made recently at all. Older ones can be fine. Really old ones I wouldn't touch though. Code enforcement and the code in general was much laxer 60+ yr ago and the pipes often weren't installed properly (lots of copper bent over someones' knee to make it fit in a tight bend, causes kinks...). Even if they were its not unheard of for copper to start leaking if there was a problem with the water or god forbid galvanized pipe was used.

Fixing in slab plumbing really does suck and you have to catch it soon after it starts or you can ruin whole sections of the slab if you don't.

5   E-man   ignore (0)   2012 Aug 7, 1:42pm     ↓ dislike (0)   quote   flag        

skinnyninja says

Their basic question is: basement or slab?

I would say basement because it is warmer like Crazy said above. I'm in CA so my experience might be a little different. Most homes built after the 90's have thicker slabs, 8 to 16 inches thick. Some homes built in the 80's have thick slabs, but most homes built before the 80's only have a 4-inch thick slab with 12 to 18 inches deep perimeter foundation. I'd say 1/8 to 1/4 cracks on 4-inch slabs are typical based on what I've seen. With a crawl space or a basement, it's much easier to make plumbing alteration. Water line doesn't get buried below the slab in the new homes.

Long story short, if you have a choice, take the basement over a slab.

6   tts   ignore (0)   2012 Aug 7, 2:04pm     ↓ dislike (0)   quote   flag        

E-man says

Most homes built after the 90's have thicker slabs, 8 to 16 inches thick.

LOL dude seriously do you have any idea how much that would cost? Remember slab foundations are supposed to be cheap.

No one does slabs that thick throughout, the edges sure for a footing, but not throughout.

FWIW I've got a 2011 home with a 4" slab and 16" footing. Also for a 3rd party reference:
http://www.ehouseplans.com/foundations.html

and another one:
http://www.concreteconstruction.net/concrete-construction/concrete-floor-slabs.aspx

E-man says

I would say basement because it is warmer like Crazy said above. I'm in CA so my experience might be a little different.

Even in CA I've seen damp and flooded basements. Depends on the water table height, soil, construction quality, etc. Basements can be great or terrible even on the same street, from the same builder too.

7   E-man   ignore (0)   2012 Aug 7, 2:13pm     ↓ dislike (0)   quote   flag        

tts says

LOL dude seriously do you have any idea how much that would cost? Remember slab foundations are supposed to be cheap.

You're just happened talking to a CA licensed foundation engineer. Not only I know about conventional slab foundation, I also know about post-tensioned slab foundation. So yes, I do know what I'm talking about.

Do you want to get a free education on deep foundation systems too?

8   tts   ignore (0)   2012 Aug 7, 2:16pm     ↓ dislike (0)   quote   flag        

Fantastic, so you've got a handy link showing residential/condo construction commonly using 8-16" thick concrete slabs throughout right?

Remember, those 3rd party links I posted dispute what you're saying pretty clearly too, so I don't care a bit about what credentials you might have.

9   37108605   ignore (0)   2012 Sep 22, 9:13pm     ↓ dislike (0)   quote   flag        

I can tell you from my family both owning and renting good size houses on slabs that they are something I would stay away from I would personally NEVER do it again.

In severe climates there can be major issues and God help you if the plumbing in below slab and a pipe breaks (been there trust me it is NOT pretty visually or financially) I would run from any place on a slab.

As for places on slabs like in FL have you have in my opinion is essentially a garage with air conditioning. Hence they these places do NOT warrant comp. money compared to something traditionally built.

I don't know where you family is looking but 300K for a condo on a slab? I just don't see it no way. I know a guy in a prime residential area in MI who purchased a beautiful colonial for under 250K with a basement.

10   Erikintx   ignore (0)   2012 Sep 23, 4:01am     ↓ dislike (0)   quote   flag        

In the case of older homes with in slab plumbing, when the time comes you just re-plumb through the attic. Had to do that at my parent's house. Your fixtures stay where they are and you just run new supply water lines through the attic. Easy on a single level house. Waste lines are still through slab but they're built with larger diameter pipe and not constantly pressurized. Having had both slab and crawlspace home I do prefer the crawlspace for maintenance and upgrades (adding in grounded electrical or running cable tv or adding Ethernet. The downside is you hear people walking around where a slab is silent.

They can insulate slabs and water barrier underneath too. That's very nice if you want a radiant heating system. It's just more expensive and thus not something you'll find on spec house construction.


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