What are the differences between:
1. Post Tension type, and
2. Pier and Grade Beam type.

I saw this in the builder's documents. Same builder but two
different cities in the same locale (Bay Area, California).
What're the implications on the soil type (e.g. would one be
used in more solid soil type, etc)?

Thanks,
Raymond

On 19 Jan 2005 08:02:44 -0800, someone wrote:

What are the differences between:
1. Post Tension type, and
2. Pier and Grade Beam type.

Well, many kinds of concrete structures can be post tensioned as well
as pre tensioned, but apparently you are talking about a slab on
grade.

Piers and grade beams sounds like a perimeter foundation. Piers are
hard points like footing with a short post on it. A grade beam is a
beam that runs along the soil (the grade) rather than spans in the air
(a "regular" beam if you will). A grade beam or a pier could, BTW, be
post tensioned....

The "documents" in construction include the drawings, but apparently
you are using the term in the more common meaning to refer to only
written word material? Really need the "plans" (actually, only SOME
"drawings" are actually "plans", the rest are sections, elevations,
details, etc.) to know what exactly is being referred to.

The design of the house as well as the soil conditions would influence
what was more appropriate.


Reply to NG only - this e.mail address goes to a kill file.

It's more a question of economics and the engineer's discretion as to which
is used - both can be equally good or bad. In residential applications,
post-tensioned is usually cheaper right now b/c less steel is used, but it
is critical that the tendons are adequately and properly tensioned. I've
looked at a lot of homes where the tendons were understressed or not
stressed at all. If going P-T I would hire a testing lab to observe the
stressing of the tendons. In either case have an engineer perfrom a
pre-pour inspection FOR YOU, not for the builder. It's amazing what the
builder's guy will pass.

Jeff


wrote in message
ups.com...
What are the differences between:
1. Post Tension type, and
2. Pier and Grade Beam type.

I saw this in the builder's documents. Same builder but two
different cities in the same locale (Bay Area, California).
What're the implications on the soil type (e.g. would one be
used in more solid soil type, etc)?

Thanks,
Raymond

Pier and Grade beam are pretty well explained by someone.

Down here common practice is to use grade beams. Piers are only used in
situations where you require a heck of a lot more strength than is
present at excavation depths or in situations where you definently need
to put your foundation on a layer of rock (for example in docks, large
buildings or houses on sandy soils vulnerable to liquefaction).

Piers tend to be more expensive than the grade beam, since they require
more work to design, more supervision in the field, and more
specialized equipment to build.

Post tensioned is probably that: some kind of grade beam with post
tensioned foundation. Might be that the technology is specific to one
company, but the builder doesn't wanna say "ABC Inc.'s post tensioned
foundation technology" in his document.

"Mario" wrote in message
ups.com...
Pier and Grade beam are pretty well explained by someone.

Down here common practice is to use grade beams. Piers are only used in
situations where you require a heck of a lot more strength than is
present at excavation depths or in situations where you definently need
to put your foundation on a layer of rock (for example in docks, large
buildings or houses on sandy soils vulnerable to liquefaction).


One exception I ran into is my home that is currently almost finished in TX
hill country. The builder would only allow a home I picked out to be built
on piers or pilings, no exceptions, no matter the grade or the soil type
makeup. The grade is slightly downslope at 3 degrees with a two foot
dropoff at the front of the house. The soil is approximately 2 inches to
nothing at the dropoff. Beneath is a one to two foot layer of caliche and
its corresponding rock type. Beneath that is fractured rock and in some
cases solid rock near the dropoff. None of which was going any place.

I decreased the dropoff later by moving the soil from the septic tank
excavation to the front of the house. Then backgraded to a more desirable
slope to the front of the house.

Piers tend to be more expensive than the grade beam, since they require
more work to design, more supervision in the field, and more
specialized equipment to build.

The builder hired out a drilling machine normally seen for the installation
of utility poles. They used a 24 inch auger bit. The average footing for
the piers was around 4 feet in depth. The workers used 1X12s for the forms
for the actual piers. The footings were tied to the piers with rebar during
the pours. They also used rebar in the piers and footing themselves. They
used a transit twice to verify the location and height of each pier before
pouring. A strip of flashing type metal was inserted to the top of the pier
during the pour and was exposed around 10 inches. This was used to tie the
pier to the sill. A wider piece of flashing was placed flat on top of each
pier where the sill actully rode on the pier.


Post tensioned is probably that: some kind of grade beam with post
tensioned foundation. Might be that the technology is specific to one
company, but the builder doesn't wanna say "ABC Inc.'s post tensioned
foundation technology" in his document.

Strange way to build a foundation - I've never seen one like that in the
Hill Country, although nothing surprises me any more. You should be OK,
unless you're on the Buda Cap formation (thin veneer of calich/limestone
underlain by highly expansive clay, almost always misdiagnosed as nonplastic
until all the cracks show up in the home a year later), of which there is a
lot around. Where exactly are you building?

Jeff


"Lil' Dave" wrote in message
ink.net...
"Mario" wrote in message
ups.com...
Pier and Grade beam are pretty well explained by someone.

Down here common practice is to use grade beams. Piers are only used in
situations where you require a heck of a lot more strength than is
present at excavation depths or in situations where you definently need
to put your foundation on a layer of rock (for example in docks, large
buildings or houses on sandy soils vulnerable to liquefaction).


One exception I ran into is my home that is currently almost finished in
TX
hill country. The builder would only allow a home I picked out to be
built
on piers or pilings, no exceptions, no matter the grade or the soil type
makeup. The grade is slightly downslope at 3 degrees with a two foot
dropoff at the front of the house. The soil is approximately 2 inches to
nothing at the dropoff. Beneath is a one to two foot layer of caliche and
its corresponding rock type. Beneath that is fractured rock and in some
cases solid rock near the dropoff. None of which was going any place.

I decreased the dropoff later by moving the soil from the septic tank
excavation to the front of the house. Then backgraded to a more desirable
slope to the front of the house.

Piers tend to be more expensive than the grade beam, since they require
more work to design, more supervision in the field, and more
specialized equipment to build.

The builder hired out a drilling machine normally seen for the
installation
of utility poles. They used a 24 inch auger bit. The average footing for
the piers was around 4 feet in depth. The workers used 1X12s for the
forms
for the actual piers. The footings were tied to the piers with rebar
during
the pours. They also used rebar in the piers and footing themselves.
They
used a transit twice to verify the location and height of each pier before
pouring. A strip of flashing type metal was inserted to the top of the
pier
during the pour and was exposed around 10 inches. This was used to tie
the
pier to the sill. A wider piece of flashing was placed flat on top of
each
pier where the sill actully rode on the pier.


Post tensioned is probably that: some kind of grade beam with post
tensioned foundation. Might be that the technology is specific to one
company, but the builder doesn't wanna say "ABC Inc.'s post tensioned
foundation technology" in his document.

A few miles northwest of Wimberley. No, I'm not the typical, uppity Houston
businessman retiree, the type that have flooded the area with their money,
increased land value beyond any reasonable expectation and their
corresponding tax values as well.
I know about the soil problems over in the Buda/Kyle area. There is no clay
out where I'm at. Forty years ago, this was considered semi-arid, almost
desert country. The juniper type cedars came along. They can and do grow
in solid rock. They also are choking out the oaks as they soak up vast
amounts of ground water, and overcrowd the oaks as well by blocking
sunlight. They create better soil conditions by actually creating soil from
rock, but at a heavy price to ground water and trees native to the area.
They love septic tanks as well.
" wrote in message
...
Strange way to build a foundation - I've never seen one like that in the
Hill Country, although nothing surprises me any more. You should be OK,
unless you're on the Buda Cap formation (thin veneer of calich/limestone
underlain by highly expansive clay, almost always misdiagnosed as
nonplastic
until all the cracks show up in the home a year later), of which there is
a
lot around. Where exactly are you building?

Jeff


"Lil' Dave" wrote in message
ink.net...
"Mario" wrote in message
ups.com...
Pier and Grade beam are pretty well explained by someone.

Down here common practice is to use grade beams. Piers are only used
in
situations where you require a heck of a lot more strength than is
present at excavation depths or in situations where you definently
need
to put your foundation on a layer of rock (for example in docks, large
buildings or houses on sandy soils vulnerable to liquefaction).


One exception I ran into is my home that is currently almost finished in
TX
hill country. The builder would only allow a home I picked out to be
built
on piers or pilings, no exceptions, no matter the grade or the soil type
makeup. The grade is slightly downslope at 3 degrees with a two foot
dropoff at the front of the house. The soil is approximately 2 inches
to
nothing at the dropoff. Beneath is a one to two foot layer of caliche
and
its corresponding rock type. Beneath that is fractured rock and in some
cases solid rock near the dropoff. None of which was going any place.

I decreased the dropoff later by moving the soil from the septic tank
excavation to the front of the house. Then backgraded to a more
desirable
slope to the front of the house.

Piers tend to be more expensive than the grade beam, since they
require
more work to design, more supervision in the field, and more
specialized equipment to build.

The builder hired out a drilling machine normally seen for the
installation
of utility poles. They used a 24 inch auger bit. The average footing
for
the piers was around 4 feet in depth. The workers used 1X12s for the
forms
for the actual piers. The footings were tied to the piers with rebar
during
the pours. They also used rebar in the piers and footing themselves.
They
used a transit twice to verify the location and height of each pier
before
pouring. A strip of flashing type metal was inserted to the top of the
pier
during the pour and was exposed around 10 inches. This was used to tie
the
pier to the sill. A wider piece of flashing was placed flat on top of
each
pier where the sill actully rode on the pier.


Post tensioned is probably that: some kind of grade beam with post
tensioned foundation. Might be that the technology is specific to one
company, but the builder doesn't wanna say "ABC Inc.'s post tensioned
foundation technology" in his document.