Dry Rot

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Dry Rot - how to diagnose

Dry Rot is extremely easy to confuse with one of the many Wet Rots, so it is important to look for several typical characteristics - a single piece of evidence can be misleading.

If in doubt contact one of our Qualified Timber Surveyors on 01626 872886 and send us some photographs of the site. Try not to destroy the evidence of Dry Rot until a firm diagnosis has been confirmed - you may also wish to advise your Building's Insurers, in case the water that caused the rot came from a leak that may be covered by your Buildings Insurance Policy.

Dry Rot must be taken seriously because it can spread beyond the area of original dampness, unlike Wet Rots which are entirely limited to the wet area and cannot travel. Always consult a Qualified expert - we can provide Contact Details for PCA Members in your area.

Dry Rot Sensors can be used to confirm that active Dry Rot is in or around the test hole - click here to look at Fugenex Dry Rot Sticks.

Early Stage Dry Rot - note the droplets  - the 'tears' of this weeping fungus

Early Stage Dry Rot - Fugenex Dry Rot Sticks react to the

Oxalic Acid produced by the fungus, by turning yellow.

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Dry Rot - main features

Look for these typical parts of the Dry Rot Life Cycle:

1. Strands - called 'hyphae' - like thin tree roots -

silvery grey to off white - brittle when dried out

(unlike Wet Rots, where Strands remain flexible).

Dry Rot strands on wood - note the deep cracks along the frain and the concave curved shrinkage

2. Skin - called 'mycellium' - dirty off white colour with

tinges of yellow or lilac at the edges (NOT brilliant white, like some Wet Rots)

Dry Rot skin hanging from a wall under a timber floor

3. Mushroom - called a 'fruiting body' or 'sporophore'

- flat rust red coloured centre area with fleshy edges in

off white to silver grey, may have flashes of yellow or purple.

The rarest form to find.

Dry Rot mushroom or 'fruiting body'

4. Dust - called 'spores' - rust red colour, like very fine talcum powder,

often covering everything around as if sprayed in a brown/red paint.

Rarely found.

Dry Rot Spores covering objects like a brown sprayed paint

5. Wood shrinkage - called 'cubing' - the wood cracks deeply

along its length and less deeply across its width, forming 'blocks' or 'cubes',

with loss of volume and sometimes curving

(unlike Wet Rots which can form lots of much smaller cubes

with even cracking along and across the wood grain).

It is unusual to find all of these together in one attack area,

so try to uncover the full extent of the rot and look closely for

each type of symptom. Remember that Wet Rots,

which require higher moisture contents,

can often be found in the same area simply because some parts are wetter than others.

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Not Dry Rot - Wet Rot examples


1. Strands - dark brown to black - flexible when dry - Wet Rot - Coniophora Puteana

Wet Rot strands of Coniophora Puteana

2. Skin - brilliant white - Wet Rot - Fibroporia vaillantii

Wet Rot skin of Poria

3. Mushroom - tiny Ink Cap mushrooms, plaster fungi

Plaster fungi Elf Cup


4. Dust - dust coming from Wood Boring Weevils -

these insects are only found in rotted timber

Wet Rot with Wood Boring Weevil


5. Shrinkage - lots of small cubing - Wet Rot - the same formation

that occurs after burning - cut our rafter feet

Wet Rotted rafter ends cut out of a roof


For more Technical Information and a Photo Gallery go to:www.timber.org.uk


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Site written by: David Moore

David Moore, B.A. (Hons.), C.T.I.S., C.R.D.S. Technical Author