How Can I Tell If I Have Dry Rot?

Updated: Sep 17, 2021

A Down and Dirty Visual Guide To Dry Rot in Roof Beams

Look for these signs of dry rot in roof beams:

paint that is peeling, wrinkled, or bubbled
cracking (especially the beam ends), sloughing, or divots in the wood
any discoloration, mold, or mildew
changes to the normal shape of the timber
anything growing on or out of the beam

Not all of these indicators will necessarily be present, but the more there are, the more likely there is significant decay.

Breaking It Down

One telltale sign of dry rot is often bubbled, distorted, wrinkled, or peeling paint:

Hidden dry rot under layers of distorted, wrinkling paint.

Bubbled up paint is a sure sign of water damage—which is the harbinger of dry rot.

Cracking on the end of the beam with a checked appearance is an indicator of significant rot (usually a brown rot):

This telltale checked appearance of dry rot in a roof beam is iconic.

Deep radial cracking is not only an indicator of dry rot, it is an avenue for spreading the problem. It can take on a variety of forms as seen in this slideshow (use the arrows or swipe):

Any change in the typical rectangular shape of a roof beam is a clear sign of dry rot affecting the structural integrity of the wood:

A roof beam will collapse in on itself when the dry rot fungus consumes all the yummy parts of the wood.

Here is a graphic example of a rotten beam being crushed under the weight of the roof load above.

Sloughing and divots also are telltale signs of extensive dry rot:

A rather wicked brown rot infection in this roof beam leaves it crumbling to dust.

This beam, which once shouldered the weight of a giant fir tree, can hardly hold itself together once dry rot had set in.

Discoloration can be the fruiting body of a dry rot fungus:

Bizarre surface growths, deep cracking and discoloration are signs of a deep fungus rot infection.

Nothing should ever be growing from your beam:

Moss and dry rot fungus thrive with moisture; this roof beam clearly drinks too much...

This roof beam clearly has a growing problem: a fungus infection old enough to produce offspring.

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