Building and Construction - new home foundation (slab??)

Author

new home foundation (slab??)

ken@claremore.net

2006-05-26, 9:21 am

I am about to build our new home in Oklahoma and am having a hard time
deciding what type of foundation to use. The home is a late 1800's
period style home - so my original plan was to build with 2' high
poured stemwall and wood joist subfloor. This plan, however, has turned
out to be quite expensive - after adding the subfloor material,
framer's uplift, hvac sub uplift and plumbing sub uplift for doing wood
floor construction.

At least 95% of the people I talk to all urge me to use slab
construction and say its better. I generally think people believe this
because that's what's prevalent in new home construction in the area,
but, I'm just not conviced (too long of a discussion for all the pro's
and con's here). So... I'm investigating the use of slab
construction...

I'm seeing immediately that there will be cost savings going with slab
construction, however, there are obviously many considerations. We
would still like to achieve the height-appearance of the period house
we're creating. We realize a full 2' won't be reasonably obtained with
slab - so I'm hearing subs tell me that they can combine a 2x12 and a
2x6 to get close to 18". This, of course, requires a lot of back-fill -
correct?

An option is obviously post-tension cabling. There are at least a
couple companies nearby that engineer the cables. This option seems to
make logical sense and I'd probably end up using this.

My primary concern with a slab is the settling and cracking. Oklahoma
is notorious for slab problems and many people make a living here
operating concrete saws and jacks - "fixing" broken slabs. I don't want
to be one of their customers down the road.

I suppose my main questions here are:

1) Would the use of drilled piers in key load points under the footings
(ie corners and inside major-load bearing walls) help much?
2) Would the combination of drilled piers (as described above) and the
use of post tension cables make sense? Or would the weight of the piers
counter-act the "pull" tension of the cables?

I just (I guess like everybody else) want to get the best foundation
for the money. I've heard that I can hire a drilling rig for about $300
to come out and drill pier holes. I'm thinking this _could_ be an
inexpensive extra insurance policy. Thanks for any experience/input!!

Needing Advice

2006-05-26, 12:21 pm

Have you factored in the additional features in your cost analysis
over a basic crawl? Coming up with the extra dough would give you the
look you desire without the worries of the possible slab problems.

I'm pretty ignorant but what are the 2*'s for? Usually plywood or
engineered forms are used to pour a foundation.

I wouldn't worry about the cost of backfill. For a slab on grade you
would only need enough to allow for proper drainage.

marson

2006-05-26, 12:21 pm

ken@claremore.net wrote:
> I am about to build our new home in Oklahoma and am having a hard time
> deciding what type of foundation to use. The home is a late 1800's
> period style home - so my original plan was to build with 2' high
> poured stemwall and wood joist subfloor. This plan, however, has turned
> out to be quite expensive - after adding the subfloor material,
> framer's uplift, hvac sub uplift and plumbing sub uplift for doing wood
> floor construction.
>
> At least 95% of the people I talk to all urge me to use slab
> construction and say its better. I generally think people believe this
> because that's what's prevalent in new home construction in the area,
> but, I'm just not conviced (too long of a discussion for all the pro's
> and con's here). So... I'm investigating the use of slab
> construction...
>
> I'm seeing immediately that there will be cost savings going with slab
> construction, however, there are obviously many considerations. We
> would still like to achieve the height-appearance of the period house
> we're creating. We realize a full 2' won't be reasonably obtained with
> slab - so I'm hearing subs tell me that they can combine a 2x12 and a
> 2x6 to get close to 18". This, of course, requires a lot of back-fill -
> correct?
>
> An option is obviously post-tension cabling. There are at least a
> couple companies nearby that engineer the cables. This option seems to
> make logical sense and I'd probably end up using this.
>
> My primary concern with a slab is the settling and cracking. Oklahoma
> is notorious for slab problems and many people make a living here
> operating concrete saws and jacks - "fixing" broken slabs. I don't want
> to be one of their customers down the road.
>
> I suppose my main questions here are:
>
> 1) Would the use of drilled piers in key load points under the footings
> (ie corners and inside major-load bearing walls) help much?
> 2) Would the combination of drilled piers (as described above) and the
> use of post tension cables make sense? Or would the weight of the piers
> counter-act the "pull" tension of the cables?
>
> I just (I guess like everybody else) want to get the best foundation
> for the money. I've heard that I can hire a drilling rig for about $300
> to come out and drill pier holes. I'm thinking this _could_ be an
> inexpensive extra insurance policy. Thanks for any experience/input!!

by backfill, you must mean fill under the slab to gain you the extra
height. there would be a cost there no doubt. also, where i live, the
building department would require an engineer for an unusual foundation
such as this...that will be an additional cost. really no way from
here to know how much. seems like you need a good plan, and then take
it to your subs and find out what plan B is going to cost. my instinct
(for what that's worth) tells me that as soon as you start doing
something unusual like perching a slab up 24" or whatever you will be
better off with wood framing and a stemwall. but thats just a guess.

tysteel3000@aol.com

2006-05-26, 12:21 pm

ken@claremore.net wrote:
....
>
> I'm seeing immediately that there will be cost savings going with slab
> construction, however, there are obviously many considerations. We
> would still like to achieve the height-appearance of the period house
> we're creating. We realize a full 2' won't be reasonably obtained with
> slab - so I'm hearing subs tell me that they can combine a 2x12 and a
> 2x6 to get close to 18". This, of course, requires a lot of back-fill -
> correct?
>
> An option is obviously post-tension cabling. There are at least a
> couple companies nearby that engineer the cables. This option seems to
> make logical sense and I'd probably end up using this.

Hi Ken,

If you are going to build a slab, I'd recommend conventional
reinforcement over using the post tension cables. You are more likely
to have a problem down the road if you use a post tension system as
opposed to just conventional rebar reinforcement. It wil cost you more
in repairs in the long haul. .

I used to work installing both conventional rebar reinforcement and
post tension systems into slabs for over 12 years. A lot of
homebuilders in san antonio started phasing in the post tension systems
because they are less expensive, but they have more problems. Even the
engineers have admitted to me that post tension systems are likely to
have a problem, and PT slabs have maybe too much movement and shifting
along with the soils, than a slab reinforced just will solid rebar.
You will end up with a lot of cracking in your walls and sheet rock.
Post tension systems in residential homes take more care....it's been
recommend by a couple of builders that you should keep the soil moist
around the slab by watering it down with a hose in cases of times of
drought and etc. The engineering companies that I have spoken to over
the years made it clear to me that if it were up to them, they'd rather
design the slabs to be reinforced with rebar instead of post tension
cables, but it's the homebuilders - who want to cut corners- who are
demanding these post tension systems.

You could get a good deal on the price of the rebar if you look around,
and maybe it won't cost too much more than using the post tension
systems. I know that if I were to build my house, I'd have it
engineered using rebar only as the reinforcement, and even if it cost
$300 more the post tension cables, I think that in the long run, it
will be worth it. I won't have to worry about repairs down the road
so much.

>
> My primary concern with a slab is the settling and cracking. Oklahoma
> is notorious for slab problems and many people make a living here
> operating concrete saws and jacks - "fixing" broken slabs. I don't want
> to be one of their customers down the road.
>
> I suppose my main questions here are:
>
> 1) Would the use of drilled piers in key load points under the footings
> (ie corners and inside major-load bearing walls) help much?
> 2) Would the combination of drilled piers (as described above) and the
> use of post tension cables make sense? Or would the weight of the piers
> counter-act the "pull" tension of the cables?
>
> I just (I guess like everybody else) want to get the best foundation
> for the money. I've heard that I can hire a drilling rig for about $300
> to come out and drill pier holes. I'm thinking this _could_ be an
> inexpensive extra insurance policy. Thanks for any experience/input!!

Craig K.

2006-05-26, 8:21 pm

post tension cables hold the slab together even if wash out under the
slab(such as a flood piers hold the slab in place and keep it level and from
shifting almost all home that have foundation problems where built before
they started using post tension cables they hold the slab toghter so if you
had a flood and your slab got washed down the street it would still be in
one piece but with both your home would still be in the same spot or at
least the slab Also be very careful when fasten to your concret slab make
shure you dont drill into your tension cable this is very important
<ken@claremore.net> wrote in message
news:1148644411.447860.40240@u72g2000cwu.googlegroups.com...
>I am about to build our new home in Oklahoma and am having a hard time
> deciding what type of foundation to use. The home is a late 1800's
> period style home - so my original plan was to build with 2' high
> poured stemwall and wood joist subfloor. This plan, however, has turned
> out to be quite expensive - after adding the subfloor material,
> framer's uplift, hvac sub uplift and plumbing sub uplift for doing wood
> floor construction.
>
> At least 95% of the people I talk to all urge me to use slab
> construction and say its better. I generally think people believe this
> because that's what's prevalent in new home construction in the area,
> but, I'm just not conviced (too long of a discussion for all the pro's
> and con's here). So... I'm investigating the use of slab
> construction...
>
> I'm seeing immediately that there will be cost savings going with slab
> construction, however, there are obviously many considerations. We
> would still like to achieve the height-appearance of the period house
> we're creating. We realize a full 2' won't be reasonably obtained with
> slab - so I'm hearing subs tell me that they can combine a 2x12 and a
> 2x6 to get close to 18". This, of course, requires a lot of back-fill -
> correct?
>
> An option is obviously post-tension cabling. There are at least a
> couple companies nearby that engineer the cables. This option seems to
> make logical sense and I'd probably end up using this.
>
> My primary concern with a slab is the settling and cracking. Oklahoma
> is notorious for slab problems and many people make a living here
> operating concrete saws and jacks - "fixing" broken slabs. I don't want
> to be one of their customers down the road.
>
> I suppose my main questions here are:
>
> 1) Would the use of drilled piers in key load points under the footings
> (ie corners and inside major-load bearing walls) help much?
> 2) Would the combination of drilled piers (as described above) and the
> use of post tension cables make sense? Or would the weight of the piers
> counter-act the "pull" tension of the cables?
>
> I just (I guess like everybody else) want to get the best foundation
> for the money. I've heard that I can hire a drilling rig for about $300
> to come out and drill pier holes. I'm thinking this _could_ be an
> inexpensive extra insurance policy. Thanks for any experience/input!!
>

mrsgator88

2006-05-27, 12:21 am

I'm curious, any reason not to put in a basement?

S

Veritas

2006-05-27, 12:21 am

ken@claremore.net wrote:

>I am about to build our new home in Oklahoma and am having a hard time
>deciding what type of foundation to use.

Well, it depends on (A) what you want, (B) what you want to pay, and,
perhaps most important, (C) what kind of soil you have.

What you need to do is get a soil test (geotechnical report) done, and
they will make recommendations as to the best type of foundation to
support the house you want to build.

As far as foundation types, here's a document that explains the
various options for expansive soils - this is the kind that's most
likely to lead to slab cracking or other foundation problems:

http://www.foundationperformance.or...FPA-SC-01-0.pdf

This is what we go by in my neck of the woods (SE Texas.)

ken@claremore.net

2006-05-29, 6:21 pm

Well, I think the 2X's are to form the stemwall. The thought is to pour
the footings, then about an 18" stemwall (using a 2x12 and a 2x6 on top
of each other as the fomrs), then backfill inside that before the slab
is poured. That's the way its been explained to me anyway.

ken@claremore.net

2006-05-29, 6:21 pm

Yes, by backfill I do mean fill under the slab to gain the extra height.

ken@claremore.net

2006-05-29, 6:21 pm

boy this goes against the trend. It seems like 95%+ of the people I
talk to say that post-tension is the greatest thing since sliced bread.
I'm wondering, however, if this isn't just another perception issue
since its the latest trend. I've always thought that the newest doesn't
always mean the best. Give me some time-tested proof.

ken@claremore.net

2006-05-29, 6:21 pm

Thanks for the input, but, i'm honestly not too worried at all about a
washout. The building site is on a the top of a hill and I can see for
miles. There is excellent drainage around all sides. The soil, however,
is somewhat rocky. Not nearly like Ozarks territory, but, a fair amount
of sandstone - some really large peices I've discovered just
sub-surface (10' long, etc).

ken@claremore.net

2006-05-29, 7:21 pm

Good question - I guess just because of cost. There is good drainage
around the location. Basements just aren't too popular around here -
even though this is tornado alley. Maybe I should research that...
however, its going to be basically the same as crawl-space with more
backhoe and concrete cost - right?

Jay Stootzmann

2006-05-29, 8:21 pm

OK? Tornado's? I'd think about a basement.

Here's a good reference
http://www.buildingscience.com/resources/homeowner.htm

<ken@claremore.net> wrote in message
news:1148644411.447860.40240@u72g2000cwu.googlegroups.com...
>I am about to build our new home in Oklahoma and am having a hard time
> deciding what type of foundation to use. The home is a late 1800's
> period style home - so my original plan was to build with 2' high
> poured stemwall and wood joist subfloor. This plan, however, has turned
> out to be quite expensive - after adding the subfloor material,
> framer's uplift, hvac sub uplift and plumbing sub uplift for doing wood
> floor construction.
>
> At least 95% of the people I talk to all urge me to use slab
> construction and say its better. I generally think people believe this
> because that's what's prevalent in new home construction in the area,
> but, I'm just not conviced (too long of a discussion for all the pro's
> and con's here). So... I'm investigating the use of slab
> construction...
>
> I'm seeing immediately that there will be cost savings going with slab
> construction, however, there are obviously many considerations. We
> would still like to achieve the height-appearance of the period house
> we're creating. We realize a full 2' won't be reasonably obtained with
> slab - so I'm hearing subs tell me that they can combine a 2x12 and a
> 2x6 to get close to 18". This, of course, requires a lot of back-fill -
> correct?
>
> An option is obviously post-tension cabling. There are at least a
> couple companies nearby that engineer the cables. This option seems to
> make logical sense and I'd probably end up using this.
>
> My primary concern with a slab is the settling and cracking. Oklahoma
> is notorious for slab problems and many people make a living here
> operating concrete saws and jacks - "fixing" broken slabs. I don't want
> to be one of their customers down the road.
>
> I suppose my main questions here are:
>
> 1) Would the use of drilled piers in key load points under the footings
> (ie corners and inside major-load bearing walls) help much?
> 2) Would the combination of drilled piers (as described above) and the
> use of post tension cables make sense? Or would the weight of the piers
> counter-act the "pull" tension of the cables?
>
> I just (I guess like everybody else) want to get the best foundation
> for the money. I've heard that I can hire a drilling rig for about $300
> to come out and drill pier holes. I'm thinking this _could_ be an
> inexpensive extra insurance policy. Thanks for any experience/input!!
>

Glenn

2006-05-29, 9:21 pm

Oh, oh. That rings a bell. I fought a million dollar house that
was built on 2 rock slabs (different height) and they were moving
apart. Know what your sub foundation is sitting on. A *lot* of
steel *may* have held them together. The house was literally
pulling apart. Finally tore it down.

<ken@claremore.net> wrote in message
news:1148937588.366231.164650@38g2000cwa.googlegroups.com
> Good question - I guess just because of cost. There is
> good drainage around the location. Basements just aren't
> too popular around here - even though this is tornado
> alley. Maybe I should research that... however, its going
> to be basically the same as crawl-space with more backhoe
> and concrete cost - right?

tysteel3000@aol.com

2006-05-30, 1:21 am

ken@claremore.net wrote:
> boy this goes against the trend. It seems like 95%+ of the people I
> talk to say that post-tension is the greatest thing since sliced bread.
> I'm wondering, however, if this isn't just another perception issue
> since its the latest trend. I've always thought that the newest doesn't
> always mean the best. Give me some time-tested proof.

Hi Ken,

I can only tell you of my experience and knowledge, as someone who
worked doing concrete reinforcement for many years. The only reason
why homebuilders use post tension over conventional rebar reinforcement
is because of price issues; not because it's necessarily better. I
know this as a fact since local builders have admitted this to me as
the reason behind their switch from conventional reinforcement to post
tension systems, and many of the engineers have made similar admissions
as well. The homebuilders simply want to cut corners and demand the
cheaper product. They are looking out for their bottom line. The
post tension is less expensive than rebar, and it's cheaper to install
by the square foot. I'm not saying that post tension won't work in a
lot of cases...all I'm saying is that you are more likely to have a
problem with it

In San Antonio, Texas, where I did slab foundation work for many years,
almost all of the homebuilders *were* using conventional reinforcement
systems on all of the slabs. There were never any problems. There
was no major business to be made by foundation repair companies. But
the homebuilders were looking to cut costs and they were demanding that
the engineering companies design the cheaper post tension systems. A
lot of the major engineering companies balked at the idea, but the
homebuilders kept pressuring them and made threats of bringing in
outside companies. A couple of outside engineering companies did
spring up, including one that was Arabian owned. And when the
engineers were compelled to design them, they were reluctant to take
full responsibility for them.

The major homebuilder in the san antonio area for many years was Ray
Ellision homes. They had 65% of the entire home market. They wanted
to start using the post tension systems because they were attracted to
the lower price, so about 20 years ago they had their engineers design
a few post tension slabs. There were problems with those foundations,
and the idea was immediately scrapped. They reverted back to
conventional reinforcement.

Then Ray Ellision was purchased by a very big builder based in
California, KB Homes. They were looking to cut costs, and their
standard wasn't up to the quality that Ellison had set. Those of us
who were doing the slab work were informed that everything was
switching over to post tension. We were told that this was happening
because they wanted a savings. They demanded that the main engineering
company do these designs. The company initially refused and another
competitor was brought in, but even then they were reluctant to take
full responsibility for the post tension slabs. They wanted the
homebuilders to take responsibilty for the slabs, since they want the
cheap stuff. A lot of the other major homebuilders also started
switching over to post tension, and this was all for price reasons.

Now, we have all sorts of foundation repair companies that have sprung
up! I'm not surprised at all. Post tension systems for residential
homes are garbage, you homebuilders who are using that crap damn well
know it, but of course you will tell the customer different. Of
course, they'll praise it to the heavens and say it's so great.
They'll tell their customers that it's better than using rebar, just in
case if the customer asks how these slabs are supposed to be as good as
the rebar reinforced ones they may spotted being used by another
homebuilder down the road. They'll never reveal to the customers the
real reason why they choose post tension over steel.

If you want a post tension slab, that is up to you, but I will tell you
that a post tension slab will be more likely to have a problem down the
road that will cost you a lot of $$$$$$ in repairs .... over using a
well designed system using conventional rebar reinforcement only.

Steve Barker LT

2006-05-31, 9:21 pm

How about a full basement? I think it would be ridiculous to do a new
construction any other way. Slabs are a pain in the XXX. My old house is
only 8" off the ground and IT is a pain in the XXX also. Crawl spaces are a
pain in the XXX.

--
Steve Barker

<ken@claremore.net> wrote in message
news:1148644411.447860.40240@u72g2000cwu.googlegroups.com...
>I am about to build our new home in Oklahoma and am having a hard time
> deciding what type of foundation to use. The home is a late 1800's
> period style home - so my original plan was to build with 2' high
> poured stemwall and wood joist subfloor. This plan, however, has turned
> out to be quite expensive - after adding the subfloor material,
> framer's uplift, hvac sub uplift and plumbing sub uplift for doing wood
> floor construction.
>
> At least 95% of the people I talk to all urge me to use slab
> construction and say its better. I generally think people believe this
> because that's what's prevalent in new home construction in the area,
> but, I'm just not conviced (too long of a discussion for all the pro's
> and con's here). So... I'm investigating the use of slab
> construction...
>
> I'm seeing immediately that there will be cost savings going with slab
> construction, however, there are obviously many considerations. We
> would still like to achieve the height-appearance of the period house
> we're creating. We realize a full 2' won't be reasonably obtained with
> slab - so I'm hearing subs tell me that they can combine a 2x12 and a
> 2x6 to get close to 18". This, of course, requires a lot of back-fill -
> correct?
>
> An option is obviously post-tension cabling. There are at least a
> couple companies nearby that engineer the cables. This option seems to
> make logical sense and I'd probably end up using this.
>
> My primary concern with a slab is the settling and cracking. Oklahoma
> is notorious for slab problems and many people make a living here
> operating concrete saws and jacks - "fixing" broken slabs. I don't want
> to be one of their customers down the road.
>
> I suppose my main questions here are:
>
> 1) Would the use of drilled piers in key load points under the footings
> (ie corners and inside major-load bearing walls) help much?
> 2) Would the combination of drilled piers (as described above) and the
> use of post tension cables make sense? Or would the weight of the piers
> counter-act the "pull" tension of the cables?
>
> I just (I guess like everybody else) want to get the best foundation
> for the money. I've heard that I can hire a drilling rig for about $300
> to come out and drill pier holes. I'm thinking this _could_ be an
> inexpensive extra insurance policy. Thanks for any experience/input!!
>

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