Decking repairs: is it the boards or the frame underneath?

The five-minute condition check

You can learn most of what you need without dismantling anything.

• Walk the whole deck and note where it flexes — flex means bearing failure, not board wear.
• Push a screwdriver into the joist ends where they meet posts or the house wall.
• Check whether the frame sits directly on soil or paving with no gap or airflow.
• Look at the fixings — corroded screws in a treated frame will keep failing.

Why joist ends fail first

Pressure treatment penetrates the outer zone of the timber. Every cut made on site exposes untreated core, and unless that cut is re-treated, it becomes the entry point. Add a joist hanger holding water against the end grain and decay is quick.

Repairing sensibly

Isolated soft boards over a sound frame are a straightforward swap. Localised joist decay can be sistered or replaced in sections. What rarely pays off is laying new boards — especially composite — over a frame that already moves, because the new surface will telegraph every bit of that movement.

Rebuild triggers

Consider rebuilding when the frame sits on the ground, when joist spacing is too wide for the board you want to use, or when the deck was built without ventilation beneath. Composite boards in particular have specific joist centres that a timber-era frame often does not meet.

Questions we're asked about this