Timber decay, dry rot, wet rot and woodwormUK building guidance
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Treatments and costs

What Affects the Cost of Replacing Rotten Floor Joists?

A damaged suspended floor needs repair and the homeowner wants a realistic quotation.

What Affects the Cost of Replacing Rotten Floor Joists? — illustrative timber damage or inspection photograph
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What might be happening

Price depends on accessibility, how many joists are affected, whether bearings or walls are damaged and how much flooring must be lifted.

Before agreeing to treatment or extensive replacement, it is reasonable to ask what has actually been found, how far the damage extends and what is allowing it to happen.

What you can look for

Ask contractors to itemise investigation, temporary support, timber work, moisture repairs, making good and waste disposal.

You do not need to start taking the building apart yourself. If access is difficult, ask the person inspecting it to explain what needs to be opened up and why. Photographs of hidden defects are useful, especially when you are comparing quotations.

Putting it right

Seek comparable written quotations after the cause and extent are reasonably established.

Be wary of a quotation that deals only with the damaged wood and says nothing about the water or building defect behind it. Once the cause has been dealt with, the remaining timber can be checked and the necessary repairs planned.

When to call someone in

An apparently cheap quote may exclude plastering, floor finishes, plumbing moves or structural design.

A carpenter or joiner may be right for a local timber repair. If the problem involves a leak, you may need a plumber or roofer first. Where supporting timbers have moved, sagged or seriously weakened, get advice from someone qualified to assess the structure.

Questions worth asking

  • What evidence supports the diagnosis and proposed treatment?
  • Which parts of the work are essential and which are optional?
  • Will you put the findings, scope and exclusions in writing?