Timber decay and woodworm
There is wet rot in the sole plate of a timber porch. Does that mean the floors inside the house are decaying?
No. Wet rot in a porch sole plate is a porch repair, because that timber sits in the weather, and it is not an inspection of the floor joists or a reason to treat the house. The Property Care Association puts moisture first: stop the plate staying wet, and replace timber that has failed. The floors were not opened because the porch was soft.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
A sole plate is the horizontal timber at the bottom of a stud wall or a porch frame. Against paving, in splash, or without a damp-proof separation, it rots. That mechanism stops at the timber that is wet. The internal floors may be metres away and dry. They may also have their own problems, hidden under coverings, which this porch does not reveal. A surveyor who writes “wet rot to porch sole plate” has named a piece of wood. They have not named the lounge joists. Do not let a quote enlarge the job from the porch to every void.
Ask whether the rot stops at the porch or whether the plate continues under the main wall, and what was actually seen. If the plate runs through, the sentence must say so, and the unseen part must be called unseen. If it is only the porch, price the porch: new plate, the weathering, and the studs that have gone soft. Do not spray the subfloor. Do not inject the house walls for a porch that stands outside them. If you want the internal floors checked, that is a separate look under the coverings, not a deduction from a soft threshold.
What should you ask your surveyor?
- Does the rotten plate stop at the porch, or does it run under the main wall?
- What is keeping it wet?
- Did you see any internal floor timber while reporting the porch?
What are the typical next steps?
- Price the porch timber and the detail that wets it.
- Do not buy a house-wide timber treatment from a porch plate.
- If the plate runs into the main wall and could not be seen, say that, and do not guess the floors.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Is a soft porch post dry rot until proved otherwise?
No. Outdoors, in wetting and drying, wet rot is the usual reading. The survey should not upgrade the fungus without evidence. The PCA still wants the moisture stopped.
Can you sister the plate and leave the rotten wood?
Only if the new timber is isolated from the damp. Burying rot in the same wet detail fails. Ask a joiner to deal with the cause.