I think I have dry rot under my sink.

Hiya Blue moon, not a very nice thing dry rot? common place for it to establish its self as it gets damp and is not very well venterlated? not hard to recognise it rots the wood so it just breaks when U touch it, is powdery and flakey and sometimes you get organic growths with it! Its very contagious and spreads, it has living spores? to eradicate it, it must be removed compleatly and the at least a meter from the point of origin? that means cutting out all affected timber upto around a meter, then treating the area with a dry rot killer including the brickwork ect, replacing timbers with treated timbers and making sure that the area is left venterlated if required. Its a must that you have it done as it will in time spread and start to affect other Timbers ect thru out the kitchen and you could have a very expensive job on ur hands? Dry rot is one of the Nasties that affects buildings? If its only a smell thats coming up it could be a lack of ventilation that is cousing it? there may just be some wet rot that is easier to deal with as you only need to remove the affected timber and a few inches past it and replace it and treat area? Hope this helps Blue moon.

There are a few things you have to look out for with dry rot (serpula lacrymans) there is normally a pungent odour that accompanies dry rot also look for fruiting body normally orangy brown fungus there will usally be brown spore dust in and around the area you will have mycellium strands in timber and brickwork dry rot has been likened to a cancer of the building as it can spread through walls and timbers causing wide spread structural damage so i would suggest calling in an expert There is aphoto on my profile of a dry rot fruiting body also you can google dry rot images hope it is not dry rot and just wet rot Good luck Steve

Superb answers from both SL solutions and Pimco, only thing to add is check extensively for leaks, even drips, the fact this is only happening under the sink could suggest you have an escape of water (thus entitling you to the cost of repairs on your contents insurance). Try filling the sink with the plug in then release it and check all the wastes while it's draining. Good luck tell tale signs other than puddled water is if the unit has swelled. Most kitchen units (strangely) don't react well to water. the edges will swell and de-laminate.