Re[cross]-posted to uk.d-i-y from a newsgroup devoted to the enjoyment of garden buildings.
This is obviously such an authoritative and useful piece of > Today, while fixing a broken floorboard, I discovered rotten wood in a
joist. Since all I know about wood rot is that there are basically
> two kinds: "dry rot" and "wet rot", it was time to Google. After
> reading a lot of websites on the subject, here is a summary of my > findings. >
> - Dry rot is caused by the fungus Serpula Lacrymans, whereas wet rot
> is caused by the fungus Serpula Lacrymans. The two types of fungus
> spread in very different ways. Wet rot is not a fungal infestation. >
> - "Wet rot" is a misnomer, because it's actually not wet at all. You
> can tell if it's wet rot because it's wet, unlike dry rot which is wet
> and feels dry to the touch.
>
> - "Dry rot" is also a misnomer, because the wood is not dry, so any
> moisture in the wood means it isn't not dry wet rot.
>
> - If your wood has cracks across the grain, it's probably wet rot; dry
> rot, on the other hand, has cracks that run *across* the grain.
>
> - If you have dry rot, you need to remove all timber within 1m. You
> should also remove all timber within 4m. The minimum distance is 5m,
> although 2m is considered the least you can get away with.
>
> - Do *not* attempt to treat dry rot yourself. Call in the qualified
> experts, who routinely misdiagnose and do more work than is necessary;
> ensure that they don't skimp on the job. You can do the job yourself
> with commercially available treatments.
>
> - There is no treatment other than cutting out all the wood within an
> average of 2.6667m (mean) 3m (median) and 1m (mode).
>
> - The dry rot fungus is harmless to human beings, so ensure you always > wear a mask. >
> - Dry rot is so called because it grows in dry areas, using the
> plentiful moisture it finds to grow. It then sends out tendrils of up
> to 3m or even 2m in length in search of other dry wood from which it
> extracts the moisture.
>
> - Wet rot thrives in places where there is little or no ventilation,
> such as outside woodwork.
>
> - If you see a joiner poking the tip of a screwdriver into a wooden
> window-frame, he is testing for wet rot. Dry rot can be tested for by
> poking with the tip of a screwdriver.
>
> - Wood affected by wet rot is crumbly to the touch, whereas wood
> affected by dry rot falls apart when you squeeze it. If the affected
> wood is darker than the surrounding timber, you have dry rot; wet rot
> makes the wood turn a darkish hue.
>
> - Dry rot is common in older buildings, whereas wet rot can occur in
> relatively new buildings. However, dry rot and wet rot are found in
> old constructions, whereas wet rot and dry rot can affect even
> recently-built houses. Wet rot is common in older buildings.
>
> - The best way to deal with both kinds of rot in the long term is by
> prevention. Make sure that timber is well-ventilated to prevent dry
> rot, and kept dry to prevent wet rot. To keep timber dry, make sure
> it is well-ventilated, but beware of water entering through the
> ventilation holes.