Anchor Spacing IRC

[Bill Kibbel]

I read about the change for '06. I thought it was a mistake. I can understand it would help in extreme areas where the earth shakes or slides and where wind or water lifts buildings, but it seems pretty silly around here. Am I the only one with these thoughts?

I saw this on Friday:

[Jim Katen]

I read about the change for '06. I thought it was a mistake. I can understand it would help in extreme areas where the earth shakes or slides and where wind or water lifts buildings, but it seems pretty silly around here. Am I the only one with these thoughts?

You're talking about the requirements in R404, yes?

The purpose of the short spacing at the bolts isn't to hold down the floor frame, it's to use the floor frame to help the foundation wall to resist lateral loading. To effectivly transfer the soil loads to the floor frame, you need a nearly continuous connection.

When you go back to inspect the framing, be sure to look at the foundation walls where the joists are parallel to the wall. There should be full-depth blocking every 24" between the first two joist bays and flat-blocking beyond that. The purpose of this blocking is to transfer the lateral loads from the foundation/retaining wall to the floor diaphragm as noted in 404.1.4.

FWIW, I built my house exactly like that back in '92.

- Jim Katen, Oregon

[Bill Kibbel]

You're talking about the requirements in R404, yes?

Correct. I was told, by a respected code official who attended a conference addressing the changes, that this was suggested for the north west coast and never intended to be applied to every jurisdiction. We don't have sliding and expanding soil, or extreme water and wind that the old anchor spacing requirement couldn't handle. There is at least one east coast state that struck R404.1 and the tables and there's movement in PA to do the same.

The purpose of the short spacing at the bolts isn't to hold down the floor frame, it's to use the floor frame to help the foundation wall to resist lateral loading.

I understand that part of the function of anchor bolts is to "pin the top" of the foundation to resist lateral force against the foundation. How well does that function with a full walk-out on a hillside?

When you go back to inspect the framing,...

I hope not - I hate new construction crap. I was only there because we have 2 guys on vacation during the busiest time we've had in years.

[hausdok]

Originally posted by Jim Katen

When you go back to inspect the framing, be sure to look at the foundation walls where the joists are parallel to the wall. There should be full-depth blocking every 24" between the first two joist bays and flat-blocking beyond that. The purpose of this blocking is to transfer the lateral loads from the foundation/retaining wall to the floor diaphragm as noted in 404.1.4.

FWIW, I built my house exactly like that back in '92.

- Jim Katen, Oregon

Jim,

Could you elaborate on that a little more. I'm having trouble understanding what you mean by "flat blocking beyond that."

OT - OF!!!

Mike

[Jim Katen]

I understand that part of the function of anchor bolts is to "pin the top" of the foundation to resist lateral force against the foundation. How well does that function with a full walk-out on a hillside?

It works fine. The force from the uphill side is transferred to the floor diaphragm where it's resisted by the bolts along each perpendicular side. There's an additional requirement for angle clips to connect the sill to the rim joist in these cases. (404.1(5))

You'd have been even more impressed with the amount of steel inside that wall.

- Jim Katen, Oregon

[Jim Katen]

Jim,

Could you elaborate on that a little more. I'm having trouble understanding what you mean by "flat blocking beyond that."

If the floor framing/diaphragm is going to be supporting the top of a foundation wall that has more than 4' of unbalanced backfill on it, the floor frame is supposed to be blocked. For the first two joist bays, the blocking is full-depth and every 24". For the remaining ones, it can be flat-blocked with (minimum) 2x4 blocks, again on 24" centers.

As I understand the section (R404), this requirement only affects wall that are 7' or taller with unbalanced backfill of 4' or more.

- Jim Katen, Oregon

[hausdok]

Hi,

Yeah, I got that the first time, but are you talking about installing blocking from wall-to-wall, with the first two blocked full depth and then blocks installed "flat" against the floor between? I still don't get it. Is there a diagram anywhere on the net that I could look at what it is your trying to drive into my dense skull?

OT - OF!!!

M.

[Jim Katen]

Originally posted by hausdok

Hi,

Yeah, I got that the first time, but are you talking about installing blocking from wall-to-wall, with the first two blocked full depth and then blocks installed "flat" against the floor between?

Yes. As I understand it, that's exactly what it says.

I still don't get it. Is there a diagram anywhere on the net that I could look at what it is your trying to drive into my dense skull?

Probably, but I've never seen it.

- Jim Katen, Oregon

[hausdok]

OK, thanks.

OT - OF!!!

M.