CRF Services Ltd
Window board fitting and internal sill replacement
The window board is the shelf on the inside of a window, often called the internal sill. It gets sun, condensation, plant pots and the odd cup of tea, and over time timber boards split, MDF swells and uPVC yellows or cracks. Window board fitting means removing the damaged board and fitting a new one that is level, tight to the frame and neatly finished at the ends. CRF Services Ltd fits window boards around Rochester and Medway, either on their own or as part of a room refresh.
Choosing the material
Three materials cover most homes, and each suits a different situation.
- Softwood or hardwood: suits period homes, can be painted or oiled
- MDF: smooth, paints well, but must be sealed against moisture
- uPVC: easy to clean, resists condensation, suits plastic windows
- Bullnose or square edge profiles to match the room
Why boards fail
Condensation is the usual culprit. Water runs down the glass, pools at the back of the board and soaks into any bare end or joint. MDF swells and lifts, timber turns black and splits. Old boards also come loose when the packing underneath shrinks. If the cause is condensation, ventilation is part of the answer, and a uPVC or well sealed timber board will last much longer than bare MDF in that position.
How a window board is fitted
The old board is carefully cut or levered out, trying not to damage the plaster or the window frame. The base is cleaned and checked. The new board is cut to length, with horns at each end scribed around the plaster returns so it fits tight into the reveal. It slides under the window frame's lip or butts tight to it, is packed level and fixed down, then the gaps to the frame and wall are sealed. Timber and MDF are primed on all faces, including underneath, before fitting.
In older houses, the reveals are rarely square, so each end is scribed separately. A board that fits well at both ends looks much better than one filled with a thick bead of caulk.
Finishing with the trim
Below the board, a small apron or architrave often finishes the junction with the wall. If the skirting and architrave are being renewed too, matching profiles across the room give a consistent finish, as covered on skirting and architrave.
What affects the cost
The number of windows, the length and depth of each board, the material, whether the old board comes out cleanly, the condition of the plaster underneath and the finishing needed all affect the price. Bay windows, with angled joints, take longer than straight boards. Window boards are part of the carpentry service. Send photos of each window and rough measurements through the contact page.
This work is part of our Carpentry service.
Common questions
Window board fitting and internal sill replacement questions answered
Useful guides
Boxing in pipes: a neat finish that still lets you reach them
Hiding soil stacks and pipe runs without trapping the valves you will one day need.
Door frame repair: what can be fixed and what needs replacing
Split linings, loose stops, broken keeps and rot at the foot, and how to tell a repair from a replacement.
Have a job in mind?
Tell Danny what needs doing and get a clear, no-obligation quotation.