What it is called, by market
One concept, four markets. Where a name means something else locally, the card says so rather than leaving you to find out on site.
United Kingdom
Same word, different thingwall plate
also sole plate, head plate
In masonry construction a wall plate is the timber bedded on TOP of the wall that rafters and joists sit on — not the top of a stud wall, which is the American sense.
Australia
Close, not identicaltop plate
also wall plate, bottom plate
Australian framing usage follows the American top/bottom plate convention, while wall plate survives for the member on masonry — so both senses are in use.
United Statesyours
Same word, different thingtop plate
also double top plate, sole plate, bottom plate, sill plate
Names the member at the top of a STUD WALL, commonly doubled. The bottom one is the sole or bottom plate, and the treated member on a foundation is the sill plate.
Canada
Same word, different thingtop plate
also sill plate, bottom plate
As the United States, with sill plate the anchored member on the foundation — a word that also means the bottom of a window opening, in the same set of drawings.
The governing standard, by market
United States
IRC Chapter 6
Wall construction, including plate sizes, splices and anchorage.
United Kingdom
BS 8103 / Approved Document A
Structural design of low-rise housing, including wall plate bedding and strapping.
Calculators for this
Each works in either measurement system, and the terminology on the page follows whichever market you have selected.
Frequently asked questions
- Which member does an unqualified 'plate' mean?
- It depends on what the wall is made of and who wrote the drawing. In British masonry construction, the wall plate is the timber bedded along the top of a masonry wall, strapped down, on which the rafters and ceiling joists bear — so it is the interface between the masonry and the roof. In North American light-frame construction, the plates are the horizontal members of the stud wall itself: a top plate, usually doubled so that joints in the two layers are staggered, and a bottom or sole plate the studs stand on. The two conventions describe different members in different positions, and a detail that says only 'plate' is ambiguous the moment it crosses a border.
- Why is the top plate doubled in North American framing?
- Because it does two jobs that a single member does poorly. It carries and distributes the load from joists or trusses above, which may not land over studs; and it ties the wall together in its length, which matters at corners, at intersections and across openings. Doubling it lets the joints in the two layers be staggered and lapped at corners and partitions, so the plate is continuous even though no single piece of timber is. British masonry practice achieves the equivalent differently, with a single wall plate lapped at joints and strapped down to the masonry at intervals — the restraint comes from the strapping rather than from a second layer.
- What does 'sill' mean here, and why is it confusing?
- Two unrelated things that appear in the same set of drawings. In North American framing, a sill plate is the timber bolted to the top of a foundation wall, usually treated because it is in contact with masonry, on which the floor structure sits. In every market, a sill is also the horizontal member at the BOTTOM of a window or door opening — a completely different component with a completely different job, and the one most readers think of first. A drawing note about the sill is therefore ambiguous unless it says which, and the ambiguity is worst in exactly the documents that mix structural and joinery information.