In an ideal world, foundations would be level and square, and
all the anchor bolts would be in exactly the right places. Of
course, nothing is ever that easy. Setting sill plates onto a
less-than-perfect foundation can be a time-consuming process of
measuring, squaring, and shimming.
A few years ago, I came up with a method that works better for
me. Before the foundation is poured, I cut and assemble the
sill plates. I do the framing layout on them, and I drill and
install the anchor bolts in the plates exactly where I want
them. Then, just after the concrete is poured, I set the plates
in place, bolts and all. I do a little thumping and tweaking,
and soon the plates are ready for framing.
I can already hear the structural engineers saying, quite
correctly, that foundation bolts should be held in place and
the concrete poured around them. Pushing bolts into partially
cured concrete displaces the stone and coarse aggregate,
leaving them sitting in a soup of cement, water, and fine sand,
a mix weaker than the design strength of the rest of the
The method required on engineered structures in seismic or
high-wind zones is to position the bolts before the pour, which
is typically done with scrap lumber, wire, or a specialized
product like Simpson's AnchorMate connector.
Often, though, on less demanding sites, anchor bolts are placed
into wet concrete. If this is done immediately, before the
concrete begins to tighten up, the aggregate flows back around
the bolts and little strength is lost.
Advantages of Wet-Set Sills
We're all aware of the things that can go wrong with anchor
bolts, no matter what method is used to set them. The most
careful preplacement rarely survives the process of pouring and
pulling the concrete through the forms — and handing a
bucket of bolts and a tape measure to the average laborer is a
recipe for disaster.
Bolts often end up under studs, joists, or posts; as a result
they get cut off or the framing members get notched. Others end
up in doorways and are cut off. If bolts are set too deep, the
sills have to be chiseled out to install washers and nuts, a
code violation. If the bolts are set too high, there might not
be enough thread length to tighten them down completely. With
my method, the bolts always end up at the proper height.
We've all experienced out-of-level foundations. Shimming sills
level or packing mortar under them can add hours to the framing
schedule. Wet-setting the sills eliminates this problem.
For simple frames, it's enough just to start the layout and
locate the bolts so that they don't land in the same places as
the joists or studs. On more complicated jobs, you need a
detailed framing plan showing the location of every piece of
wood in the first level of the structure.
I used to draw the plan on paper, then give the foundation
contractor an anchor-bolt plan worked out to the inch. But I'd
still have to fit the sills to the bolts and the framing to the
sills, and hope that everything lined up. Now I do the initial
framing plan directly on the sills, eliminating several steps.
This saves time and minimizes errors.
Probably my biggest challenge used to be setting
engineer-specified bolts for anchoring hold-downs. Making a
mistake would require an expensive, time-consuming fix using
epoxy and threaded rod.
On the project shown here, a simple two-story garage, the plans
required hold-downs in shear walls at every corner. With the
layout done ahead of time, the anchor bolts were perfectly
aligned for the hold-downs to attach to the wall framing.
Prepping the Sills
To begin, I cut the sills and assemble them in the lengths of
the framed floors or walls. I'm careful to use straight stock,
because there isn't any way to brace the sills straight in the
In our area, we use double sills; the bottom one is
pressure-treated, the upper one standard framing lumber. If
there will be a conventional floor frame on the sills, the two
layers can be permanently spiked together; if the upper sills
are wall bottom plates (as on the slab foundation in the
photos), I just tack them so that I can later remove the upper
sill and build the walls lying flat.
Next, I establish a common layout for the building in both
directions, which keeps the joists, studs, and rafters in line
from sill to ridge. As I mark the layout on the sills, I can
often shift other framing elements slightly to reduce waste and
avoid odd-sized bays (see Figure 1). For example, all the
double studs for the shear walls in this garage incorporated
one stud on the common layout.
With the garage-wall bottom plate
tacked to the mudsill, the author marks the stud layout, making
adjustments as needed so that the anchor bolts don't interfere
with the framing (top). He checks the placement of a hold-down
bolt (middle) using the actual hardware, and labels each set of
plates (bottom) in preparation for concrete.
I locate and mark any critical hardware, such as shear-wall
hold-downs, so that no framing ends up in the way of these
connectors. It's best to have the actual hardware on hand, or
at least exact specifications, so the bolts can be set at the
right distance from the members they attach to. I also locate
any bolts specifically called for by code, such as those within
12 inches of beam pockets or corners.
If the top sills are also wall bottom plates, I lay out the
framing for the entire wall, including studs, cripples,
openings, posts, shear-wall studs, and any other framing
members. Then I locate the anchor bolts where they meet code
and make sense. For example, the building code or an engineer's
spec might call for anchor bolts 32 inches on-center, but at a
doorway it's clearly better to place the bolts just beyond the
king studs on either side.
When I'm satisfied with the layout, I drill the holes and
install the bolts in the sills. I label, organize, and store
the completed sills, then wait for concrete.
During the Pour
The guy who does my concrete formwork does a good job of
stringing, squaring, and straightening the forms. To keep the
sills square, I follow the forms, but I check his work with
diagonal measurements. As each section of the forms is filled,
I trowel the wet concrete smooth, working to grade nails set in
the forms (Figure 2). Then I'm ready for the sills.
Figure 2. As soon as a section of wall is
poured (top), the author trowels the concrete to the correct
level (top right). The plates — bolts and all — are
then set into the wet concrete (bottom).
Handling the sills usually requires a couple of helpers.
Together we set the sills in place inside the forms. Where the
sills overlap at the corners, I tack the lapped corners
together, squaring and straightening them carefully as I go.
When I'm satisfied with the placement of the sills, I carefully
push the bolts into the concrete as plumb as possible, making
sure the nuts are threaded on the bolts consistently (Figure
As the pour proceeds, the crew works
quickly to position the plates (top) and push the anchor bolts
into the concrete (bottom two photos).
Next I station a crew member on a transit or laser level and
check the sills for level. When I've found the lowest point, I
go around and thump the rest of the sills down to that level
with the head of a sledge hammer (Figure 4). I drive a nail
through the forms every few feet to hold the sills in place
while the concrete cures. Occasionally, I'll need to use a
brace or block to hold a sill straight.
Figure 4. While the concrete is still
plastic, the crew finds the lowest point on the foundation,
then uses a sledge to tap all the plates to that elevation
(top). Here the author checks the short garage-wall plates for
After the forms are stripped, I check the sills for square and
level again. If minor adjustments are needed, I can always shim
or plane them a bit. Small lateral adjustments can be made by
shifting the upper sills and elongating the bolt holes slightly
if necessary. But generally none of these tweaks are
The concrete tends to ride up along the sides of the sills,
particularly in areas where they had to be thumped down. On the
inside, this is not a problem, but on the outside, I flake off
the excess concrete with a hammer claw so that the wall
sheathing can be run down and nailed to the bottom plate
Figure 5. After the forms are stripped
(top), the author uses a claw hammer to remove the irregular
ridge of concrete along the side of the sill (middle). The
finished result is accurately placed hold-down anchors and
foundation bolts (bottom).
On the garage shown, the entire sill-layout process took me a
couple of hours before the pour. (I was working alone with no
distractions.) Setting and adjusting the plates during the pour
took less time than just measuring and setting the bolts would
John Spier owns Spier Construction on
Block Island, R.I., with his wife, Kerri Spier.