Rotten door frames and sills: repair, splice or replace

Test the extent, not the surface

Push a bradawl or a screwdriver into the suspect area. Sound timber resists; rotten timber takes the point with no effort. Work upward and sideways until you meet firm timber — that boundary is what decides the repair.

• Soft only in the bottom 100–150mm of the jamb: a splice is usually viable.
• Softness rising up the jamb or into the fixings: replacement is the sensible route.
• Sill soft along its length: replace the sill, then re-check the jamb feet.

Why it happened matters more than the repair

The usual causes are a failed or missing drip detail under the sill, a raised external ground level bridging the threshold, a blocked weather bar, or paint applied over damp timber and sealing the moisture in.

A repair that ignores the cause simply resets the clock. Where the ground level is the issue, the frame repair has to be paired with a drainage or threshold change.

Splicing done properly

A good splice cuts back to sound timber on an angled scarf, uses a species and section that matches the original, is fixed and bonded rather than filled, and is primed on all faces — including the hidden ones — before it goes in. Two-part filler over soft timber is not a repair; it traps water behind a hard shell.

When to replace the whole frame

If the frame is out of square, the fixings have lost their hold in a rotten section, or you are already changing the door, a new frame gives you a proper weather detail and a door that closes evenly. It is also the point at which insulation and draught detailing around the reveal can be corrected.

Questions we're asked about this