I have to replace a rotten mudsill at the front of my house. I have read that timber frame sills have to be spliced in with a half lap joint. This makes sense for a timber frame sill, but do you need to splice old and new (2x6) sections of mudsill together? If so, how would you do this. BTW it is really only the mudsill that is damaged. The rimjoist above is fine.
Thanks for the help.
mudsills are usually held in place by anchor bolts which are cast into the concrete foundation. i think it would be best if the splices were anchored by bolts on either side, but in practice, noone around here does that--they just toenail the splice together. in a retrofit situation, you would probably be fine just pusing in a section of sill and toenailing the rim joist to it.
however, if you live in a seismic zone then anchoring the house to the foundation is a much bigger deal, and you would need to likely retrofit some seismic anchors. in any case, it's the attachment to the foundation that counts more than the splice in the sill.
snipped-for-privacy@veriz> I have to replace a rotten mudsill at the front of my house. I have
Thanks,
When you say splice them together, do I have to use any particular kind of joint to join them or can I butt the new section right up against the old one?
Thanks again.
Ok, thanks.
The foundation is on hollow cement blocks. It seems like it would be easy to fill the hollow spaces with concrete, push the predrilled sill in place, then jam some threaded rod through the holes into the concrete...intstant sill anchors.
Thanks again.
It's nice when things turn out to be easier than normal. You're lucky. I'd probably revise the threaded rod in mortar, though. There's not much uplift resistance with such an installation. If you drilled the sill plate holes a bit oversize, say 5/8" or 3/4" holes, you could insert a wood or plastic dowel while the concrete sets up, then remove the dowel and use anchor bolt setting epoxy (comes in caulking tubes from the Borg or other home centers and is absurdly strong) to set the threaded rod.
If you're a belt and suspender type of guy you could use stainless threaded rod. It's the preferred material when the fastener is in contact with ACQ treated lumber. Larger diameter fasteners don't necessarily have to be stainless, but threaded rod has that minimal plating and that doesn't last too long.
Another alternative would be to cut elongated holes in the plate that would let you insert hot-dipped galvanized anchor bolts, commonly called J-bolts, in the wet concrete. Use oversized galvanized washers to cover the enlarged holes. Let the concrete cure for a few weeks before cranking down on the nuts.
R
Just butt them together. Here are some notes about anchor bolts:
Sill anchor bolts shall be hot dipped galvanized or stainless steel, 1/2" minimum diameter, with a minimum embedment of 7 inches, unless noted otherwise on Shear Wall Schedule or Foundation Details. Bolts shall be tied in place prior to pouring concrete and shall not be "wet-set" or "stabbed" into wet concrete. Bolts shall be spaced at no more than 48 inches o/c. There shall be a minimum of two bolts per piece of sill plate, with one bolt located not more that 12 inches and not less than 7 bolt diameters from each end of the piece. Field drilled Hot-dipped galvanized or stainless steel concrete wedge-type anchors of the same diameter with a minimum embedment of 3-1/2" may be substituted for embedded anchor bolts. Wedge anchors, if used, shall be installed with a square plate washer as noted below.
Anchor bolts for treated sill plates shall be provided with 3"x3"x1/4" hot-dipped galvanized square steel plate washers between the sill plate and the nut. The hole in the plate washer is permitted to be diagonally slotted with a width up to 3/16" larger than the bolt diameter and a length not to exceed 1 3/4", provided a standard cut washer is placed between the plate washer and the nut.
Hey Bob. Why do you require such a large plate washer when anchor bolts generally have ~1.5" washers? Is that a seismic design requirement?
R
I would suspect that is the case. Here is an excerpt from my last NSPE electronic newsletter.
Matt
Researchers at the University of Buffalo recently used a pair of "shake plates" simulating California's 1994 Northridge earthquake to test a
1,800-square-foot three-bedroom house, the largest wooden building that has ever been subjected to such a simulation. According to engineering professor Andre Filiatrault, at least 80 percent of buildings in the United States are made of wood--and 90 percent of residential buildings are so constructed--"and yet we know very little of how they perform in earthquakes." In the simulation, the windows shimmied, the stucco cracked in a few places, and a station wagon moved a few inches on the garage's concrete floor, but there was no evident structural damage. "If the contents were properly anchored, you would have survived in that building, no doubt," said Colorado State University professor John W. van de Lindt, the principal investor on a national project that seeks to improve wood-frame construction's safety and economics. An infant's swing in the house stayed upright in the simulation, and a full water pitcher on a table did not spill its contents, indicating that there would not even have been much cleanup necessary. Built with West Coast-style stucco siding and clay roof shingles and up to California housing codes--including the use of some techniques common since the 1994 quake, such as larger washers for bolting a sill plate to the concrete floor--the house had already stood up to several test quakes. The next step in the four-year project, financed by the National Science Foundation, will be to analyze data from the house's 250 sensors to help with designing larger wooden structures.
IBC2003 Section 2308.12.8 and IRC Section R602.11.1 require a 3"x3"x1/4" size plate washer for Seismic Design Category D (or C in the case of townhouse construction). Note: for IBC this was changed from 2"x2"x3/16" in the 2004 amendments.
Because 99.8% of my designs occur in Seismic Design Category D, the large washer has become a standard part of my specs.
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