Advised my Victorian chimney is porous!??

[Deansplit]

I live in a Victorian terrace, built in 1898. I have 2 chimneys, each with 3 flues. Only the front is used (by only one solid fuel fire). A couple of yrs back I noticed damp in the ceiling and wall below the rear one, then also a smaller amount in the front one. We had the roof at the front done and I also had the flashing done to the rear chimney.

However, my neighbour is saying he has bad damp (6-8ft across!) in the area below my rear chimney. I said I had the flashing done, although noticed there was still ongoing penetrating damp in our rooms too. The guy who did the flashing said it's soaking up the water and because it's not in use, is just dripping down the walls, both sides, but seems to be worse on next doors side. The neighbour has since had a structural engineer out, who says a similar thing - that it's porous!

I'm not doubting a professional opinion, but these 2 people are friends of the neighbour!... but how can a rendered chimney let in so much damp? Surely, the rest of the rendered house would be drenched too being that it's the same material built at the same date??

If it's all true, what's my options apart from removing totally, or stripping it down, inserting new lead soakers and rebuilding a false one? Can it be re-rendered, or something applied to it to prevent the penetration of rain??

Many thx for any advice.

 

[JohnD]

are the disused chimneys (especially your neighbour's) ventilated top and bottom? Often fireplaces are bricked up preventing ventilation, and this causes condensation due to the warm moist air from the house getting into the cold chimney through the porous bricks and not having an airflow to dry it out.

this need not cause a draught, most often an airbrick is put in when the fireplace is bricked up, but it is sometimes possible to do it with ventilation under the floor.

If there is a bathroom and/or kitchen at the back these are especially prone to high humidity and damp, especially if an extractor fan is not used during and after every bath or shower, or if anyone likes to drape wet washing about the house.

The least troublesome approach I know with a (fully) disused chimney is to remove the stack down into the loft, where it can be left open, and make good the roof above it. This is a bit of a building job, though, but it removes the need for future re-pointing and flashing work.

 

[Deansplit]

Hi - forgot to mention, the breast below it on the top (2nd) floor was removed prior to us moving (6yrs ago) - but the damp wasn't apparent then (not as visible as it is now, with probs on the neighbour's side anyway). It's definitely got worse. In fact, a fair amount of the damp is visible on the underside of casing in the top room (covering the I beam which the chimney's now supported by).