How to detect dry rot

Written by smokey yokems
  • Share
  • Tweet
  • Share
  • Pin
  • Email
How to detect dry rot
Damp wood timbers can be a source of devastating damage throughout your home. (Wood image by filipkaluzny from

Dry rot is the common term for the decay of wood caused by the presence of the fungus Serpula lacrymans. Serpula lacrymans spores are common, flourish in wood with a moisture content of 25 to 30 per cent, and are active in temperatures between 18 and 32 degrees Celsius (65 and 90 degrees Fahrenheit). Dry rot usually starts in enclosed damp locations, under floor boards, at baseboards and in ceiling joists. In advanced stages, the fungus sends out strands that can travel through dry concrete and masonry to attack distant wood sources. This extremely damaging fungus can literally suck the structural integrity out of a building from the inside out. Early detection is key to preserving your property.

Other People Are Reading

Things you need

  • Torch (Flashlight)
  • Screwdriver
  • Metric drill
  • Dry rot sensors

Show MoreHide


  1. 1

    Examine the underside of floor boards, deck floors and roof timbers for source fungus. In early stages, dry rot looks like white cotton sheeting. Fungus exposed to light may have a silkier appearance. Advanced dry rot will create a mushroom smell and may produce an orange/brown pancake type growth on the wood exterior.

  2. 2

    Examine neighbouring timbers for extended spore activity. Dry wood that has been attacked internally by dry rot may have dark stains or pale stains. Affected wood may also appear abnormally dry or cracked. Fully damaged beams or boards will easily break apart in your hands.

  3. 3

    Knock on wood beams that appear healthy further from the source fungus. If dry rot exposure has started from within, a beam with normal appearance may sound hollow. Use a screwdriver to penetrate the wood. If damage is developing, the tool may easily break through the surface.

  4. 4

    Insert dry rot sensors into areas you suspect may be in early stages of dry rot that is not yet visually or manually detectable. Dry rot sensors have been treated with a chemical dye that changes from blue to yellow when exposed to oxalic acid, a byproduct of dry rot activity. The test will require you to drill a 7 mm (1/4 inch) diameter hole in either wood or masonry to a depth of 100 mm (4 inch) and insert the dowel. The chemical reaction takes up to 14 days and will detect the presence of dry rot prior to any notable damage.

Don't Miss


  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.