Raised foundation vs. slab foundation
John Louie
Hello, I live in Southern CA and have noticed
most newer homes 1960+ are built on concrete slabs.
I am wondering about the pros and cons of concrete
slabs as opposed to raised wood foundations. Also
if concrete slabs are so bad why not go back to
raised wood foundations?
Here is what I have so far.
Pro Slab
Cheaper for the builder
No termites under the house
More rigid in an earthquake, more likely to stay intact
Con Slab
Plumbing difficult to repair
Extra cable/phone outlets need to be added in the attic
Concrete is harder on the feet
Less give in an earthquake, more likely to not stay intact
Please email me if you have more to add.
Bob and Ellen Curry
I'd be interested to know where you got the data that slabs are more
likely to stay intact than a pier/beam foundation. Years ago, I
researched foundation types when I lived across the street from the
San Andreas fault and found that pole barn foundations were probably
the best for residences. The problem with slabs was that they tended
to throw the house off the slab when the ground waves went through.
Cost is usually the main reason for the wide use of slabs since lumber
and labor prices have increased over the years. Still, in the finest
homes in our area, you rarely find slabs -- almost always a pier/beam.
bob curry
danh...@millcomm.com
In <3542EA...@earthlink.net>, John Louie <jlo...@earthlink.net> writes:
>Hello, I live in Southern CA and have noticed
>most newer homes 1960+ are built on concrete slabs.
>I am wondering about the pros and cons of concrete
>slabs as opposed to raised wood foundations. Also
>if concrete slabs are so bad why not go back to
>raised wood foundations?
>
>Here is what I have so far.
>
>Pro Slab
>Cheaper for the builder
>No termites under the house
>More rigid in an earthquake, more likely to stay intact
>
>Con Slab
>Plumbing difficult to repair
>Extra cable/phone outlets need to be added in the attic
>Concrete is harder on the feet
>Less give in an earthquake, more likely to not stay intact
I would think a treated wood foundation would be as cheap and earthquake
proof as a slab. The main difficulty is that too many people are afraid
of the concept.
Dan Hicks
Hey!! My advice is free -- take it for what it's worth!
http://www.millcomm.com/~danhicks
ces...@earthlink.net
In article <3542EA...@earthlink.net>,
jlo...@earthlink.net wrote:
>
> Hello, I live in Southern CA and have noticed
> most newer homes 1960+ are built on concrete slabs.
> I am wondering about the pros and cons of concrete
> slabs as opposed to raised wood foundations. Also
> if concrete slabs are so bad why not go back to
> raised wood foundations?
>
> Here is what I have so far.
>
> Pro Slab
> Cheaper for the builder
> No termites under the house
> More rigid in an earthquake, more likely to stay intact
>
> Con Slab
> Plumbing difficult to repair
> Extra cable/phone outlets need to be added in the attic
> Concrete is harder on the feet
> Less give in an earthquake, more likely to not stay intact
>
You are comparing a "crawl-space" foundation (not a wood foundation) to a
slab-on-grade foundation. The footings in a crawl-space type are still
concrete (not treated wood).
The OLD crawl space foundations were bad in an earthquake because they had
unbraced, wood-framed, pony walls between the foundations and the first floor.
Current construction would use a concrete stem wall or shear-panelled wood
stem walls. A modern crawl space foundation should be equal to a
slab-on-grade.
The biggest difference is cost. S-O-G is cheaper on a level building pad
(typical development). If you have a rocky or very sloped building pad, crawl
space will be cheaper. Crawl space is much easier to make future repairs
within, rather than cutting up a slab.
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Joe Supulski
Scratch 'no termites' under your house from the PRO list...I just had a
townhouse I own built on a slab treated for termites...The swarmers came
up through the living room floor through the cracks in the concrete that
WILL ultimately develop...Right thru he rug..
The treatment was to drill through the entire slab on the first floor
every foot or so which meant in my case removing the rugs and
wood floors and replacing them...Total cost for treatment and new floors
exceeded $2000 for a 600SF 1st floor...
As a builder I am a FIRM believer in an ACCESSIBLE Crawl space under ALL
conditions...I not only look at the bottom line for what it costs ME NOW
but what it will cost the OWNER to maintain in the future...
Joe Supulski
General Contractor
Pennsylvania
SAUNDRSMNH
Some of the answers you have gotten are not too accurate.
The slab on grade is a cheaper way to build the house, and it aslo has some
advantages over a raised floor. The slab will NOT throw the building off.
There is so much wrong with that statement, I do not know where to begin).
Wood foundations are not a good alternative, especially in California.
The response about the pony walls was correct - if not constructed properly,
they will collapse in an earthquake. There is more to it. The interior posts
and beams need to be well interconnected also, or else there is a possibility
the posts or beams will slide and collpase. Also, with a slab, the interior
partitions will be at least nominally anchored to the slab with pins, thus they
will contribute to the lateral (earthquake) strength of the house - they also
will be less likely to slide than a sill plate nailed into plywood.
However, the main reason the developers like slabs is the cost - not just the
cost of the slab, but the reduction in time to erect the building when a slab
is used.
-Rob, S.E.
Topher Eliot
John Louie <jlo...@earthlink.net> wrote:
>Hello, I live in Southern CA and have noticed
>most newer homes 1960+ are built on concrete slabs.
>I am wondering about the pros and cons of concrete
>slabs as opposed to raised wood foundations. Also
>if concrete slabs are so bad why not go back to
>raised wood foundations?
>
>Here is what I have so far.
>
>Pro Slab
>Cheaper for the builder
>No termites under the house
Not if you get a crack in the slab, and who doesn't? The
crack would likely be hidden from view. With a crawl
space, at least you have a chance at inspecting and finding
the termite evidence.
Topher Eliot
el...@alum.mit.edu
Visit the house maintenance archive at http://www.geocities.com/heartland/7400
Don
Topher Eliot wrote:
>
> John Louie <jlo...@earthlink.net> wrote:
>
> >Hello, I live in Southern CA and have noticed
> >most newer homes 1960+ are built on concrete slabs.
> >I am wondering about the pros and cons of concrete
> >Pro Slab
> >Cheaper for the builder
> >No termites under the house
>
> Not if you get a crack in the slab, and who doesn't? The
> crack would likely be hidden from view. With a crawl
> space, at least you have a chance at inspecting and finding
> the termite evidence.
Termites will hang about under a slab house if the soil is damp and
especially if there is wood waste or leftover timber formwork. Termites
won't chew through 4 inches of solid concrete. They will however, open
up cracks in very poor concrete and they can walk right through the gaps
where slabs are not properly vibrated. If you make sure the slab is
wellplaced, the fill is compacted, the rebars are right, the concrete is
the proper strength and not excessively thinned and it is placed so as
to expel the trapped air and it is thick enough and the footings are
adequate and the concrete is allowed to cure before subjected to load
then termites coming through the slab shouldn't be a problem!
Cheers
Don
--
Dr Don's Termite Pages
http://www.labyrinth.net.au/~dewart
It's better to be controversial for the right reasons,
than to be popular for the wrong reasons. -Shimon Peres
Sandy
> John Louie <jlo...@earthlink.net> wrote:
>
> >Hello, I live in Southern CA and have noticed
> >most newer homes 1960+ are built on concrete slabs.
> >I am wondering about the pros and cons of concrete
> >slabs as opposed to raised wood foundations. Also
> >if concrete slabs are so bad why not go back to
> >raised wood foundations?
> >
> >Here is what I have so far.
> >
> >Pro Slab
> >Cheaper for the builder
> >No termites under the house
>
> Not if you get a crack in the slab, and who doesn't? The
> crack would likely be hidden from view. With a crawl
> space, at least you have a chance at inspecting and finding
> the termite evidence.
I've lived in both slab and raised foundation homes, and of course there
are pros and cons to each. Overall I prefer a slab because of the home's
quietness and stability. The cracking, popping, and other "settling"
noises on a raised foundation home are endless, while I don't recall ever
hearing them on a slab foundation home. Of course, on a slab foundation if
you have to repair a pipe buried in the concrete, you regret it...
-- Sandy
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"Whatever you can do, or dream you can, begin it.
Boldness has genius, power, and magic in it." --Goethe
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