Flat or V-Groove Jamb Extensions: How to Choose
A replacement window, new drywall over old plaster, or insulation added to a wall all leave the same problem: the frame stops short of the finished wall surface, and the casing will not sit flat against it.
A jamb extension fills that depth. It fastens to the edge of the existing jamb and brings it out flush with the wall, so the casing has something to sit on.
Flat extensions
A flat, square profile in finger-joint pine, primed on all sides. We carry it in two thicknesses, 23/32 in and 3/4 in, so measure the thickness you need as well as the width.
| Face width | Thickness | Length |
|---|---|---|
| 1 5/8 in | 23/32 in | 192 in |
| 2 3/8 in | 23/32 in | 192 in |
| 3 1/2 in | 23/32 in | 84, 96 or 192 in |
| 4 5/8 in | 23/32 in or 3/4 in | 192 in |
| 5 1/2 in | 3/4 in | 192 in |
| 7 1/4 in | 3/4 in | 192 in |
| 9 1/4 in | 3/4 in | 192 in |
V-groove extensions
The same idea with a shaped edge, all 3/4 in thick and 16 ft long. If you are replacing a piece, the edge has to match as well as the width and thickness.
| Face width | Thickness | Length |
|---|---|---|
| 1 3/8 in | 3/4 in | 192 in |
| 2 3/8 in | 3/4 in | 192 in |
| 3 3/8 in | 3/4 in | 192 in |
| 4 5/8 in | 3/4 in | 192 in |
| 7 1/2 in (special order) | 3/4 in | 192 in |
| 9 1/2 in (special order) | 3/4 in | 192 in |
The two ranges do not share every width, so check the table for the one you are matching. See the V-groove extensions.
How to measure
- Depth to cover: from the face of the existing jamb to the finished wall surface. That is your face width.
- Thickness: match the existing jamb or extension.
- Length: the two sides and the head of each opening.
- Replacing a piece? Bring an offcut or a photograph of the end so the edge can be matched.
We cut extensions to size. Give the counter the finished cut list and ask about cutting and delivery. For the trim that goes over the extension, see door and window casing.
Bring the profile or an offcut, the sizes and the number of lengths to the counter in Concord, Barrie or Mississauga, and we will confirm the order before you travel.