West Glamorgan · Wales
Floor joist repairs in West Glamorgan
If you live in West Glamorgan and are looking at floor joist repairs, the first question is why the wall moved. West Glamorgan has a mix of ground, with clay in some places and firmer rock in others; historic coal workings are recorded beneath parts of West Glamorgan, and a coal mining search is worth checking where movement is unexplained.
Guide price from£230per joist inc VAT

- Area
- West Glamorgan
- Pricing region
- Wales
- Ground
- Clay in parts
- Towns listed
- 4
Is West Glamorgan prone to ground movement?
Swansea and Neath Port Talbot lie on the South Wales coalfield, with historic workings, tips and steep valley sides, and softer estuarine ground around the docks.
Historic coal workings are recorded beneath parts of West Glamorgan, and a coal mining search is worth checking where movement is unexplained. What you mostly find across West Glamorgan: hillside terraces, Victorian villas in Swansea and post-war estates.
What to look for before calling about floor joist repairs
- Floor dipping towards an outside wall or in the middle of the room
- Soft or spongy boards near outside walls, hearths or the bathroom
- A musty smell, or fungal strands showing between the boards
- A gap opening up between the skirting board and the floor
Floor joist repairs prices in West Glamorgan
Guide prices below are for homes in West Glamorgan, on Wales rates and including VAT. A survey or good photos let us turn them into a fixed written price.
| Item | Guide price | Per |
|---|---|---|
| Splicing or sistering a damaged joist | £230 – £370 | per joist |
| Whole room of joists and boards | £1,850 – £5,500 | per room |
| Sleeper wall rebuild and ventilationest. | £370 – £1,400 | per room |
How we usually approach floor joist repairs
Sistering a joist
A new length of treated timber, the same depth as the original, is bolted or screwed alongside the damaged joist so the two share the load. It is the quickest fix for a notched, cracked or sagging joist that is otherwise sound, usually after lifting a few boards.
Best for: Cut, cracked or sagging joists with sound ends
Splicing ends and fitting hangers
Where only the end has rotted, it is cut back to sound timber and a new piece is fixed alongside, bearing on the wall or on a new joist hanger. Missing or under-nailed hangers elsewhere are replaced at the same time. The damp in the wall must be fixed too.
Best for: Rotten joist ends in damp solid walls
Sleeper walls and ventilation
Settled or damp sleeper walls are rebuilt on a sound base with a damp-proof course under new timber plates. Blocked air bricks are cleared, extra ones added where the void has dead spots, and soil or paving heaped against the outside wall is lowered.
Best for: Damp ground floor voids or joists on poor supports
What happens during floor joist repairs, step by step?
Lift boards and inspect
On site we lift a few boards where the floor is worst and check the joist ends, sleeper walls and void with a moisture meter. Outside, we look for high ground, blocked vents and leaks keeping the timber wet.
Written quote
You get a no-obligation written quote listing which joists are sistered, spliced or replaced and any sleeper wall or ventilation work. It becomes a fixed price in writing once the repair is specified.
Repair the structure
Boards are lifted and numbered if they are going back, and rotten timber is cut out. New treated timber is fixed and checked with a level before strutting, hangers and any restraint straps go in.
Do you need approval for floor joist repairs in Wales?
In Wales, small like-for-like repairs do not usually need approval, but work that alters or strengthens the structure needs building control under the Welsh Building Regulations, and the Party Wall etc. Act 1996 can apply to shared walls.
Find floor joist repairs in your West Glamorgan town
Questions about floor joist repairs in West Glamorgan
Why do houses in West Glamorgan crack?
Swansea and Neath Port Talbot lie on the South Wales coalfield, with historic workings, tips and steep valley sides, and softer estuarine ground around the docks. Historic coal workings are recorded beneath parts of West Glamorgan, and a coal mining search is worth checking where movement is unexplained. Only an investigation on site can say why a particular building has moved.
How much will floor joist repairs cost in West Glamorgan?
On Wales rates, floor joist repairs starts from about £230 per joist, including VAT. The written price depends on the extent of the damage, access and whether an engineer or building control is needed.
What is sistering a floor joist?
Sistering is fixing a new length of timber alongside an existing joist so the two share the load. It strengthens a notched, cracked or sagging joist without removing it, so it is quicker and less disruptive than replacement.
What causes rot in floor joists?
Damp causes almost all joist rot. Joist ends in damp walls, voids with blocked air bricks, leaking pipes and high outside ground levels keep timber wet enough for fungi to grow. Replacing timber without fixing the damp usually means the rot returns.
Do I need building control for floor joist repairs?
Usually not for like-for-like repairs to a few joists, but replacing a whole floor structure can be building work. In Scotland that generally needs a building warrant, and in Northern Ireland council building control applies. We deal with building control where the work needs it.