colorado house

[go do it]

here is a post that i placed @ CONTRACTOR TALK

more brains never hurts

thanks for the replies

drilled post and grade beams for colorado house

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hey i need more info from you guys if you don't mind

the house i am looking to do in CO. the architect has called out for a drilled post and grade beam foundation

is this common for CO?

it seems like overkill to me but i am not from CO.

they want the post socket or the portion of the post drilled into bedrock to be 10' to 11' long and the total post length to be 20' min. DAMN

so my questions are:

are their more economical ways to deal with expansive soils that everyone up there will be comfortable with?

are post-tensioned slabs used ever

of course we will do what is needed

but DAMN

38 holes drilled 10' into bedrock with 4 #5 rebar tied with #3 rebar hoops every 24" and the filled with concrete and on top of that a reinforced concrete grade beam

just imagine the piers that are built for bridges and overpasses that is the process

thanks

[Dick Seibert]

Everything we do in California is pier and grade beam, that came in about 1974, the engineers won't stick their names on a T foundation anymore. Have your rebar tied by a shop and delivered on the job ready to drop in the holes. I'd check those specifications closely, usually the depth of the piers is called out based upon the soils engineer's report; however, look for the words "Or to refusal". They never expect you to drill into solid rock, it's impossible, so once you hit refusal you can stop. You must have the soils engineer present to certify that you have actually hit refusal and aren't just shorting the holes though. The biggest problem with deep piers is you have to keep them clean, and that's the hardest part, even with an engineer's letter all inspectors carry a little mirror and catch the sun just right to check the bottoms of the holes for loose dirt, I've had to clean out the bottoms of 40' deep piers and that isn't any fun, I had a machine shop build me a long device to clean out the bottoms of deep piers.

[go do it]

thanks

we have never done one of these before

here everything thing is slab on grade

thats the great thing about construction new things to get the excitement going again

[Martin Holladay]

Dick,
I defer to your expertise about pier and grade beam foundations, since I've never done one. But I'm surprised by your statement, "They never expect you to drill into solid rock, it's impossible." Don't you have well-drilling rigs in California? It's a very useful piece of equipment, used all the time in Vermont -- not only for drilling 300-foot-deep (or deeper) wells through solid granite, but occasionally for setting steel bollards or gate posts in difficult soil.

[BillHartmann]

There was an article a few years ago about expansive soild in CO. I think that it was in JCL, but might have been FHB.

Don't remember the details of the footing/foundations.

But the basement floor was a slab suspended off the foundation walls so that there was a gap between it and the ground.

[Toolwhore]

Everything we do in California is pier and grade beam, that came in about 1974, the engineers won't stick their names on a T foundation anymore.

Not in all of CA, Dick. Everything I've worked on here (SD), and when I lived on the west slope of the Sierras, was SOG (no piers), except for one project that was a sub-division of 3 story townhouses, built on piers (in SD), on that terrible Caleechi (sp?) clay (expansive soil) they have in some places down here.

The biggest problem with deep piers is you have to keep them clean, and that's the hardest part, even with an engineer's letter all inspectors carry a little mirror and catch the sun just right to check the bottoms of the holes for loose dirt, I've had to clean out the bottoms of 40' deep piers and that isn't any fun, I had a machine shop build me a long device to clean out the bottoms of deep piers.

Boy, that brings back bad memories! I was the skinny 17 yr. old at the bottom of the food chain that they lowered into the 45 ft. holes on a rope, with a bucket to clean out those pier holes. Inspector made us clean out about 65% of the 148 holes. I was sure the big earthquake was gonna hit, every time I was at the bottom of each hole. It was extremely unnerving.

Martin,

They do have well drillers here. I drilled water wells in the Sierras for a couple years, back in the 80's. Some were over 700 ft. deep, through solid granite, but they were only 12" in diameter, not the 24"-36" that foundation piers are usually poured at.

[Dick Seibert]

Martin:

Don't you have well-drilling rigs in California?

I've never used a well driller, we have companies who specialize in drilling foundations, I've never checked their bits, but when the drill the soils engineer is always there, off and on, and he tells them when they can stop. I've used Hillside Drilling for the last 40 some years, when I went to their website I was surprised to see that they say 31 years, I can drive to projects they drilled for me over 40 years ago, the contact name is different though, it was two brothers with a different name most of the time and I do remember an ownership change, but the name has always been Hillside Drilling.

Tom:

As you know, California is really at least three different states, and should be divided up. In our area SOG is reserved for commercial/industrial and cheap tract homes, nobody wants a custom home on a slab; however, with the current preference for limestone floors in the upper end SOG (but not PTSOG, they were a disaster with lawsuits all over the place) has made an appearance. SOG also was used in some contemporary custom homes with all glass walls, and even in tracts like Eichler Homes, Eichler went bankrupt though because he used radiant heat in his slabs, when the black iron pipe rusted out there were lawsuits all over the place, his defense was that copper pipe wasn't available in the 50s when he started, true, but bronze pipe was.

When an architect designs a contemporary home in our area now (very rare in this age of McMansions) and wants a concrete floor, the engineers always put piers under the cast-in grade beams, no more thickened edge stressed cable slabs to heave and float up and down.

[Overbuilders]

Hey, I need more info from you guys if you don't mind. The house I am looking to do in CO, the architect has called out for a drilled post and grade beam foundation. Is this common for CO? Of course we will do what is needed. But DAMN. 38 holes drilled 10' into bedrock with 4 #5 rebar tied with #3 rebar hoops every 24" and the filled with concrete and on top of that a reinforced concrete grade beam

Here in Jefferson County, CO, every lot in every subdivision has been tested, some multiple times, for expansive soils. Bentonite runs in veins here, so your next-door neighbor's house can and will have different requirements. If you are building a deck, you simply call the Bldg Dept and they tell you what the caisson size will be. And yes, you are required to drill to whatever depth the AHJ specifies.

[Overbuilders]

Just remembered, I built an addition on a house in Arvada (Denver suburb in JeffCo) three years ago. The existing foundation was 42"h x 10"w on a 6"h x 18"w spread footer, so I was allowed to use those specs for the addition. No caissons required.

[Dick Seibert]

you simply call the Bldg Dept and they tell you what the caisson size will be. And yes, you are required to drill to whatever depth the AHJ specifies

Where are your lawyers in Colorado? Our AHJs require individual soils reports on each project with the foundations designed based upon those reports, then the plans sealed by the Design Professional of Record, our AHJs won't take any liability at all, seems like with every crack in the sheetrock some smart lawyer would be suing the city.

[Overbuilders]

Where are your lawyers in Colorado? Our AHJs require individual soils reports on each project with the foundations designed based upon those reports, then the plans sealed by the Design Professional of Record, our AHJs won't take any liability at all, seems like with every crack in the sheetrock some smart lawyer would be suing the city.

Sorry, thought I explained it with this statement:

Here in Jefferson County, CO, every lot in every subdivision has been tested, some multiple times, for expansive soils.

[Dick Seibert]

Rick:

Yes, but you indicate that the AHJs are taking those reports and passing out free engineering, they assume the liability, and at least in California a soils engineer can't buy liability insurance, so they are assuming all liability. In California soils engineers haven't been able to buy liability insurance for over 50 years, they incorporate a string of successive corporations then bankrupt them as the claims amass. I once was reviewing the County history of a site I was thinking of buying in a slide prone area, the names of the same soils engineers kept coming back through a string of different corporate names, many of these guys I knew or use to know, so I questioned one of them and he told me that's what they had to do since no insurance company would insure a soils engineer since their "science" was so inexact.

[CB Rob]

Its pretty common up here in the hills. The homes in the valley bottoms get to sit on a typical footer, but the ones getting built on the side of the mountain are sitting on piers. sometimes its a bunch of 8" micropiles, and sometimes a big 24" pier every 20 feet. They go till they hit rock, and then a little more.
We don't have issues with the soil heaving, just settling down hill.

[go do it]

it has been very interesting investigating the soils up in co

the soil from pueblo to wyoming is bad it seems according to the colorado geological survey

being from nm we seem to not have a problem with soil movement

except when a whole subdivision is built over a landfill

yes it was done
it's like building over buired baloons

i have found instances where the soil lifted 3" in 24 hrs. after a rainstorm

i beleive it was in colorado springs

drilled post and grade beams make more sense to me now

drill the post into bedrock "place" the grade beams on top and let the soil run up and down the post

[Sweep8]

They never expect you to drill into solid rock, it's impossible, so once you hit refusal you can stop.

I have worked on buildings in Massachusetts where multiple sockets were drilled into rock to provide uplift resistance.