The Sill That Suddenly Feels Soft
The window looks fine.
No misted glass. No obvious water pouring through the frame. Nothing around the handle or hinges suggests a problem.
Then somebody presses down on the internal window board.
It moves.
Paint starts bubbling around the edge and the MDF underneath feels soft enough to mark with a fingernail.
MDF Really Hates Water
Plenty of internal window boards are made from moisture-resistant MDF rather than solid timber.
That works perfectly well in a dry room.
Repeated moisture changes things quickly.
MDF is made from compressed wood fibres bonded together. Water gets into an exposed cut edge or damaged surface and those fibres begin swelling.
The board gets thicker. Corners become fluffy. Paint cracks away from the surface.
Drying it afterwards does not magically compress those fibres back into their original shape.
Bournemouth Windows Get Plenty of Moisture
The important job is finding out where the water came from.
A leaking frame is one possibility. It is not the only one.
Condensation running repeatedly from cold glass can collect along the back edge of the board. Failed sealant around the internal frame junction can let that moisture reach an unfinished MDF edge.
Bournemouth’s wet coastal weather can expose external sealing defects too. Wind-driven rain finds small gaps around frames and reveals that stay completely dry during calmer conditions.
One damp winter can leave the board looking worse every month.
Find the Wet Edge
Start at the damage.
A swollen section directly below one corner of the frame gives you somewhere to investigate. Look for water staining, cracked sealant and paint lifting away from the board.
Check the window after heavy rain. Check it again on a cold morning with condensation across the glass.
Those are two different moisture sources and they need two different fixes.
Deal with the water before replacing the board.
Badly swollen MDF normally needs cutting out rather than sanding endlessly back into shape. Fit the replacement neatly beneath the frame, seal vulnerable cut edges and finish the frame-to-board junction properly.
A new sill sitting underneath the same leak will eventually look exactly like the old one.
Trade Counter Supplies
A soft window board is usually the damage you can see. Finding the moisture behind it is the important bit.
Head down to DWC Trade Windows at 78 Alma Road, Bournemouth for window sealants, replacement components and advice on repairing the window area properly.
Call us on 01202 533126 for window and glazing supplies in Bournemouth.
