Dry Rot but can't find source

[Sam Fairlie-Clarke]

I live in a terraced house (approx. 100 years old) and I've found some Dry Rot (mould with rusty coloured centre) coming out of the adjoining brick wall between my neighbour's property and mine. I cannot however find any infected wood. I've stripped back all the plaster, wood, etc. right to the external and adjoining wall. I've also been and checked my neighbour's house who does not have any sign of it. I'm no expert but it was my belief that Dry Rot needs wood to feed on and shouldn't be able to grow on mortar. I'm at a loss to think where the Dry rot may be feeding.

The rot is in the corner of the house where there was originally a press cupboard so has affected one wall which is external to the rear of the property and the other which is the adjoining wall to the neighbour.

There has been a bit of rot in a joist and in the lintel above the press cupboard which I am getting replaced but I think that was wet rot as didn't have any of the cracking associated with dry rot. All other wood I can see looks pretty sound.

There had also been some leaking in the roof above the area affected which has been repaired. The pointing was also repaired in the portion of the external wall that was damp and is slowly drying out. (This is taking ages as it is the external sandstone wall and it never stops raining in Scotland!) The only thing I can think of where water could still get in is the chimney flue. One of these has not been capped and the fireplaces have not been vented where they were blocked up. Could this be the source of the Dry Rot?

I've searched for rotten wood round the affected area to a distance of a couple of metres; should I be looking further away as well? All the strands from the rot seem to be coming from the adjoining wall. Does it sometimes travel in circuitous routes?

I would be very grateful for any help/suggestions people could give as it's driving me crazy!

 

[Burnerman]

The hyphae from the dry rot fungi can happily travel through masonry Sam, but its pretty difficult to determine where the source has been.
Have a look for the various treatments that are around for spraying onto the brickwork.
Have you looked beneath the floorboards near the affected area?
John

 

[gregers]

your wall plates may well look ok from the front,but may well be totally rotten behind where the rot has traveled.
you need to do more investigation to the surrounding area.

 

[DaveHerns]

Sorry to be thick but what is a press cupboard?

 

[JohnD]

press means cupboard. more often heard in the Northern parts of the British Isles.

e.g. hot press means airing cupboard

cf "linen press"

 

[vinn]

It could be that the roof leak has infected the wood at the eaves and the fungus has travelled down the wall behind the plaster infecting other wood on the way.
Go into the loft as close to the eaves as possible and search for signs.
If you have a cavity wall then it can travel through a cavity.
It could be that the unvented and maybe unswept flues have been the route for the dry rot. Open the blocked fireplaces and look.
Do you mean a first floor joist (not a lintel) above the press?
Why not lift some floorboards and examine the joists in what seems to be the chimney breast recess in the 1st and GF floors, and also remove and examine the skirting.

 

[Sam Fairlie-Clarke]

Thanks for all the suggestions.

I've checked the floor joists in the loft and they are all structurally sound. There is a small amount of rot in the lintel above the cupboard. It is a wooden lintel and supports the brick wall above it. An end of the roof truss that fixes into the rear wall also has rot. Both of these are rotted for a couple of inches of wood, however, there was no sign of the dry rot fungus or hyphae around them. Could they be the source? if that's the case, would they still have dry rot around them?

I'll give opening up the fireplace a shot as it may shed some more light on the affair.

 

[vinn]

You can have wet rot and dry rot in the same area.
The idea in the loft is to get tight to the eaves and look at the area where the leak was.
Do you have a room with floor joists in the loft? Or do you mean the ceiling joists?

But its hard to get a picture of what you have without some photo's?

 

[Sam Fairlie-Clarke]

Sorry, meant the ceiling joists. I've looked as tight as I can to the eaves and the wood there is ok. Had a problem with water getting in under the slates that run next to the skew between my house and the neighbour's. It's been fixed but I can't get in to see if any of the wood there has been rotted as it sits on top of the adjoining brick wall. All the wood I can see there looks ok but there is about 6+ inches that I can't see. I'll get some photos uploaded tomorrow to try to make it clearer.