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.
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.
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
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.
In a previous post email@example.com wrote...
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.
Bob Morrison, PE, SE
R L Morrison Engineering Co
I would suspect that is the case. Here is an excerpt from my last NSPE
4. 'This Is a Test. In the Event of an Actual Earthquake...'
New York Times (11/15/06); Staba, David
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.
Bob Morrison, PE, SE
R L Morrison Engineering Co
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