What is a dutchman repair?

A dutchman repair is a traditional timber repair in which the decayed part of a component is cut out and replaced with a closely fitted new piece of wood, the dutchman or insert. It keeps as much original material as possible and is widely used on windows, doors, frames and sills of historic buildings. In Dutch the technique is called ‘uitstukken’.

Method

Find the extent of decay: probe with an awl or screwdriver to see how far the rot goes.
Cut out: remove the affected wood generously, back to sound timber, with straight, clean faces.
Make the insert: use the same species, the same grain direction and, ideally, a similar moisture content to the existing wood.
Fit and fix: fit the piece tightly and fix it mechanically, for example with timber dowels or stainless steel screws.
Profile and finish: plane the insert to match the existing moulding and repaint.

The five steps of a dutchman repair, from finding the extent of decay to profiling and repainting the insert.

Removable or glued?

The Dutch heritage agency (Rijksdienst voor het Cultureel Erfgoed) prefers removable, unglued joints for historic windows and doors. The part can then be taken out again for a later repair, and a new sill, for example, is easily fitted into an old frame. In everyday renovation, inserts are often glued or epoxy is used. For a listed building elsewhere, check with the relevant heritage authority which approach it expects.

Approaches as described in the article. The preference for removable joints is that of the Dutch heritage agency (Rijksdienst voor het Cultureel Erfgoed) for historic windows and doors. For a listed building elsewhere, check with the relevant heritage authority which approach it expects.

Dutchman or splice?

With a dutchman, the new piece sits within a component, where the decayed wood was removed. With a splice or scarf repair, a component is lengthened with a new piece at its end, such as the foot of a frame post.

Application

Typical spots are the feet of frame posts, bottom rails and sills, sash corners and the bottom rails of doors: anywhere water tends to sit.

Tips and points of attention

Screws on the inside: place screws only on the inner side of the rebate, so no water can track along a screw into the wood on the outside.
Same species: a different species moves differently, causing cracked paint or open joints.
Fix the cause: repair weatherboards, sealant and paintwork too, or the rot will return.
Listed buildings: work on a listed building may need consent.

Related terms

Wood rot
Restoration
Listed building
Door sill
Wood joints

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