wood sill plate anchorage on concrete basement walls
wood sill plate anchorage on concrete basement walls
(OP)
I have a question regarding sill plate anchorage requirements. The 2000 IRC requires that the wood sill plate be anchored to the foundation with 1/2" anchor bolts at a maximum of 6' on center. What I am concerned about is a basement wall that retains earth. The sill plate is typically pressure treated southern pine, with the bolts loaded perpendicular to the grain. Because the load is permanent, Cd is 0.9. Therefore according to the NDS the strength of one of these bolts is 400 X 0.9 = 360 pounds. With an 8 foot basement wall retaining 6 feet of granular soil, the reaction at the top of the wall can be approximately 230 plf. Multiplying this by 6 feet gives you 1380 pounds, which is way more than the bolt capacity. My soil pressure is based on at-rest conditions, since the wall is prevented from yielding by the floor diaphragms. According to the NDS, even a 1" bolt is only good for 700 pounds before any adjustment factors.
I know that the code establishes a minumum requirement, but for most residences all I usually see is the 1/2" anchor bolt at 6 or 8 foot spacing, which appears to be inadequate.
Am I missing something here??
I know that the code establishes a minumum requirement, but for most residences all I usually see is the 1/2" anchor bolt at 6 or 8 foot spacing, which appears to be inadequate.
Am I missing something here??





RE: wood sill plate anchorage on concrete basement walls
RE: wood sill plate anchorage on concrete basement walls
RE: wood sill plate anchorage on concrete basement walls
Years ago I( started spacing the 1/2" bolts at 4'-0" oc. The numberes still don't work, but its a little better.
I think the friction force of the house is what helps a little and must make up the difference.
RE: wood sill plate anchorage on concrete basement walls
I would like to hear from some of the people from the ICC what the justification for the minimum anchorage requirement is.
RE: wood sill plate anchorage on concrete basement walls
If the walls are too long then they start to behave like you describe (pinned at the top and bottom).
I think this anchor bolt requirement is a holdover from the days when structures were relatively small and the walls were short. The prescriptive codes do not get updated as often as the engineered codes do and there is alot of momentum not to change from the Contractors.
RE: wood sill plate anchorage on concrete basement walls
We've got to focus instead on the most important issues. Like multiple permits, inspections and approvals to replace the water heater, or reshingle the roof, or replace an old toilet fixture.
RE: wood sill plate anchorage on concrete basement walls
RE: wood sill plate anchorage on concrete basement walls
RE: wood sill plate anchorage on concrete basement walls
The sill plate on the wall perpendicular to the joists has the benefit of a toenailed joist every 12-16 inches, plus the rim joist, plus friction.
As I may or may not recall correctly, I felt overall the plywood deck could play only a minor role in offering meaningful lateral support for the foundation wall.
The owner of a local excavation company did my backfilling.
He was a small old man, bowlegged and lame, but his machine was nimble and quick when he was at the controls. I remember watching him work and thinking he could have gently tied his granddaughter's shoelaces with the bucket. When I suggested we get the deck on before he did any backfiling, he said in his opinion it really didn't matter much.