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Additions on Piers

steveray

steveray

SAWHORSE
Joined
Nov 25, 2009
Messages
13,758
Location
West of the river CT
Somewhere between a framing and foundation question....has anyone found a prescriptive way to have braced wall panels with an addition on piers? 602.10.8 Gives connections of BWP to the "foundation" which is assumedly prescriptive....with anchor bolts 6' OC and so on.....is it strictly DP land or are people accepting piers 6' OC w/ bolting? All of the contractors keep looking at me like I am crazy....the old "do you know how many I have done" stuff.

Anyone else dealing with this?

Thanx!
 
It can be done, all the shear will need to be transfered into the beam (over the piers) then into the piers.
 
"In the 30 years we’ve been building homes we’ve never had anyone question us on these 2 issues. I’m just trying to understand what it is that you ultimately want us to do."

FOLLOW THE BUILDING CODE OR GET A DESIGN PROFESSIONAL!

Thanks folks! Just need that reassurance that I am not being unreasonable every now and then.....
 
steveray said:
Somewhere between a framing and foundation question....has anyone found a prescriptive way to have braced wall panels with an addition on piers? 602.10.8 Gives connections of BWP to the "foundation" which is assumedly prescriptive....with anchor bolts 6' OC and so on.....is it strictly DP land or are people accepting piers 6' OC w/ bolting? All of the contractors keep looking at me like I am crazy....the old "do you know how many I have done" stuff.Anyone else dealing with this?

Thanx!
Click to expand...
6' appears to be the prescriptive spacing for hold down bolts. As long as the girders are designed for the loads I don't see any problems. But I don't have plans in front of me.
 
Here is what the code says.

R602.10.7 Braced wall panel support. Braced wall panel

support shall be provided as follows:

1. Cantilevered floor joists, supporting braced wall lines,

shall comply with Section R502.3.3. Solid blocking shall

be provided at the nearest bearing wall location. In Seismic

Design Categories A, B and C, where the cantilever

is not more than 24 inches (610 mm), a full height rim

joist instead of solid blocking shall be provided.

2. Elevated post or pier foundations supporting braced wall

panels shall be designed in accordance with accepted

engineering practice.

And from the commentary.

Elevated post and pier foundations

Elevated post and pier foundations generally provide little

lateral support to the structure above. Lateral support

instead typically comes from diagonal bracing or other

elements of the foundation; however, there are ways of

cantilevering the posts of the foundation by burying the

ends deeply into the ground, so that they develop lateral-

load-resisting characteristics.

It is difficult to accurately and fully present all of the post

and pier lateral support methods in one set of prescriptive

provisions. For this reason, post and pier foundations supporting

braced wall panels must be engineered in accordance

with the IBC or referenced documents, as stated in

the Section R602.10.7, Item 2.
 
"Elevated post and pier foundations generally provide little lateral support to the structure above."

I guess that would only be for non-code compliant structures. Code compliant structures provide sufficient lateral support.

The engineering required mostly depends on the local construction practices. It might be that local construction practices provide sufficient lateral support and engineering is simply pro forma.
 
Thanks Mule! Is that 2006 or 2009? My 2003 does not read that way......I still came to the same conclusion....but nice to have a code clarification or something easier to spoon feed people....
 
Anytime.....2009 IRC.......... LOTS and I mean LOTS of changes to the 2009 windbracing section. In the 2009 IRC you can have a "floating" wall brace line. The braced wall line does not necessarily have to be "on" a wall.

For anyone that has not or has recently adopted the 2009 IRC the windbracing section will take a while to understand it. I think the reason is because the code went from just seismic to seismic and wind category. You have to include wall height and ridge height into the calculations for the amount of windbracing required. If you don't have a wall long enough to get the required wall bracing you will have to use an interior wall for windbracing AND have a beam under the wall AND install anchor bolts in that interior wall.
 
For this reason, post and pier foundations supportingbraced wall panels must be engineered in accordance

with the IBC or referenced documents, as stated in

the Section R602.10.7, Item 2.
Click to expand...
We just adopted the '09, can you throw me a bone on the referenced documents?
 
The statement quoted above is from the commentary so I believe the referenced documents is the IBC and the IRC.

There are specific details in Chapter 3 of the 2009 IRC that pertains to the designing of structures based on the new windbracing requirements.
 
Braced Wall Lines

Here's another note to throw in the back of the brain. This is all new to the builders and designers so they don't have a clue as to how to design the structure. There may be walls that will need to be moved because of interior wall bracing. The foundation may have to be redesigned to comply with an interior beam under a braced wall.

This is new to the engineers also. Just because they are engineers does not mean that they are familiar with the windbracing requirements. There are wind categories, wind speed, seismic, wall height, ridge height, type of windbracing (CS GP LI and others) that need to be figured in to determine how much windbracing is required. If one of the BWL's is an exterior wall and the designer needs to continue the BWL on through on an interior wall, then the wall needs to be calculated as gyp board and not as the type of windbracing used on the exterior wall. This means that you will need more windbracing than originally thought.

When you have CS there is a chart that specifies how much you can count towards the windbracing based off of the height of an opening.

Also from the review standpoint you need to make sure that the bracing is within 12.5 feet of the end of the BWL and every 25 feet. This can get tricky when you have interior BWL's. However the floating BWL helps to meet the requirements.

Sorry for hijacking the thread. Sometimes I get on a roll and can't stop. :oops
 
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