Llanelli · Dyfed
Floor joist repairs in Llanelli
Floor joist repairs in Llanelli start underneath the boards, not on top of them. We look at the joist ends, the sleeper walls and the ventilated void before suggesting sistering, splicing or replacement, so the price reflects the timber you actually have.
Guide price from£230per joist inc VAT

- Postcodes
- SA15
- Population
- about 50,000
- Area
- Dyfed
- Pricing region
- Wales
Is Dyfed prone to ground movement?
Llanelli is in Dyfed and takes in postcode districts SA15. About 50,000 people live there. Nearby, we also cover Gorseinon (5 miles), Swansea (10 miles) and Ammanford (11 miles).
Most of Dyfed is on firmer ground than the clay belts of the south-east. Parts of Dyfed lie on a former coalfield, so a coal mining search is worth checking if movement has no obvious cause. What you mostly find across Dyfed: stone cottages, Victorian terraces in Llanelli and Carmarthen, and post-war estates.
From first photo to finished repair
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.
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.
Relay and ventilate
Boards are relaid or replaced, skirting refitted and air bricks cleared or added outside. We point out anything that would let damp back in, such as soil heaped against the wall, so the repair lasts.
Symptoms that point to floor joist repairs
- A musty smell, or fungal strands showing between the boards
- Soft or spongy boards near outside walls, hearths or the bathroom
- A gap opening up between the skirting board and the floor
Guide prices for floor joist repairs in Llanelli
The ranges below reflect typical Wales costs for floor joist repairs, including VAT. Scaffold, access and making good can push a job to the top of the range.
| 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 |
Methods for floor joist repairs
Replacing joists and boards
When rot or woodworm runs through most of a floor, it is usually cheaper to replace the joists, strutting and boards together. Where joists run parallel to an outside wall, restraint straps tie the new floor back to it so the wall keeps its lateral support.
Best for: Widespread rot, or a whole floor that has dropped
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
Rules 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.
Frequently asked questions
What is the price of floor joist repairs in Llanelli?
Guide prices for floor joist repairs in Llanelli start from about £230 per joist, including VAT, on Wales rates. Your fixed written price follows photos or a survey and depends on the extent of the work and access.
Do you carry out floor joist repairs in Llanelli?
Yes, Llanelli is covered, along with postcode districts SA15. We also cover nearby Gorseinon and Swansea.
Does the ground around Llanelli cause cracking?
The western edge of the South Wales coalfield lies beneath Llanelli, Ammanford and parts of Pembrokeshire, while the rest of the area is older hard rock with glacial deposits in the valleys. Only an investigation can say why a particular building has moved.
Will my insurance pay for rotten floor joists?
Usually not, because rot, woodworm and gradual wear are standard exclusions. Damage from a sudden escape of water, or a floor that dropped through subsidence, may be treated differently. Check your policy, and tell your insurer before permanent repairs start if either applies.
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.
More repairs we carry out in Llanelli
- Crack stitching
- Structural crack repairs
- Subsidence repairs
- Extension pulling away repairs
- Mining subsidence repairs
Floor joist repairs near Llanelli
Each joist, sleeper wall and air brick at your Llanelli property is itemised in the written quote, then fixed in price once the repair is specified.