Construction glossary · Wood framing
What is sill plate in construction?
A sill plate, also called the mudsill, is the bottom horizontal member of the frame that sits directly on top of the foundation wall or slab and anchors the building to it. It is pressure-treated lumber bolted down with anchor bolts and is the first piece of wood the framer sets. The takeoff is the linear feet of foundation perimeter plus the anchor bolt count from the bolt spacing.
Updated June 2026 · Reviewed by the Ruh construction team
Sill plate on foundation
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Book a walkthroughThe sill plate is the pressure-treated bottom plate that bears on the foundation and transfers the wall loads down while tying the structure to the concrete against uplift and sliding. Because it contacts concrete, code requires it to be naturally durable or pressure-treated lumber, and a sill sealer or capillary break goes between the wood and the concrete. It is fastened with cast-in-place anchor bolts, or epoxy or wedge anchors in retrofit, set at a maximum spacing set by code, commonly 6 ft OC, with a bolt required within a set distance of each plate end and at every plate splice. In seismic and high-wind zones, plate washers and tighter spacing or hold-downs are added per the structural notes. For the estimator the sill plate is two takeoffs that run together: linear feet of treated plate around the foundation perimeter, and the count of anchor bolts and their washers and nuts driven by the spacing and the end and splice rules.
Sill plate is taken off in linear feet of treated lumber equal to the foundation perimeter, read off the foundation plan. The anchor bolts are counted from the bolt spacing called out in the structural notes, commonly 6 ft OC maximum, plus one bolt near each end and at each splice. The bolt count is the perimeter divided by the spacing, then add bolts for ends and corners per the notes. Pull the bolt diameter and embedment, the plate washer size, and the sill sealer width from the foundation detail. Treated plate is ordered by linear foot in standard lengths; sill sealer is ordered by the roll to match the perimeter and plate width.
Worked example
A 160 lf foundation perimeter, single 2x6 treated sill plate, anchor bolts at 6 ft OC. Plate lumber = 160 lf of treated 2x6, ordered in standard lengths. Anchor bolts by spacing = 160 lf / 6 ft = 26.67, round up to 27 bolts for the field spacing. Add 1 bolt within 12 in of each plate end and at the corners; for a simple 4-corner rectangle that is roughly 4 to 8 extra bolts, so call it 27 + 8 = 35 anchor bolts with 35 plate washers and 35 nuts. At an illustrative 2.75 dollars per bolt with washer and nut, hardware is 35 x 2.75 = 96.25 dollars before the treated plate and sill sealer.
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How Ruh handles sill plate
Ruh reads the foundation plan, takes off the sill plate as linear feet of treated lumber around the perimeter, and counts anchor bolts from the bolt spacing in the structural notes plus the end, corner, and splice rules. It prices the treated plate, bolts, plate washers, and sill sealer on your own price book. The estimator confirms the bolt spacing, embedment, and washer call against the structural notes and seismic or wind requirements, then signs off.
See framing estimating softwareSill plate: frequently asked questions
How many anchor bolts for a 160 lf foundation at 6 ft OC?+
160 lf divided by 6 ft is 26.67, so 27 bolts for the field spacing. Then add one bolt near each plate end and at corners and splices, which usually brings a simple rectangle to the low-to-mid 30s.
Why does the sill plate have to be pressure-treated?+
It sits directly on concrete, which holds moisture, so code requires naturally durable or pressure-treated lumber to resist rot. A sill sealer or capillary break goes between the wood and the concrete as well.
Is sill plate the same as a bottom plate?+
No. The sill plate or mudsill sits on the foundation and is treated and bolted down. The bottom plate is the untreated bottom of an interior or upper wall framed on the subfloor above. They are taken off and priced separately.
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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.