Damp chimney wall with soft mortar

[scoobydoo]

We've just moved into a small semidetached house - approximately 1820'ish.

It has some visible damp in the upstairs bedroom at the top of the chimneybreast wall, above the sealed fireplace. The fireplace downstairs is open, and there doesn't seem to be any damp downstairs nor any signs of water. I had the chimneybreast replastered while we were getting some other work done so that it would be really clear where the water is coming in. The exposed beam joining the chimney breast to the ceiling looks like it's gotten damp at some point, and the top of the wall looks to be the worst, but the rest of the wall doesn't seem to have dried as well as I would have expected (wonder if the majority is coming through the top and not making it's way down the wall)?

The wall never gets wet, but does feel damp and cold to the touch after it's rained (at the top where it's worst). Today I went into the loft to look at the chimney bricks above it and, whilst it looks ok, the mortar is very(!) soft! I could push the mortar inbetween the bricks (only did it once then panicked!). Again there are no visible signs of water anywhere but I take it this isn't right?..... One of the bricks seemed a bit soft too - uh oh!

So, my senses tell me that water is somehow getting into the chimney (it has a very basic cowl on it but looks visibly ok from outside), then somehow getting through the chimney and into the wall. I had a roofer pop round and have a quick look and he said the roof looks ok. There are no visible signs of water anywhere which is making this hard!

Can anyone suggest what to do now (other than staying well away from the chimney?!) The only things I can think of are:

--- Have the chimney breast wall in the loft repointed

--- Consider ripping all the plaster off the chimney breast in the bedroom and repointing the whole wall (even though I don't know if there's a problem with it)...

--- Get a different chimney cowle to try to stop the water (is this even possible?)

--- Consider getting the chimney relined (don't really want to do this if it's going to be really expensive - would it really be required?)


Help! Can anyone give me some pointers (excuse the pun), guides to cost and / or reassurance that the house will still be standing tomorrow(!)?

Can anyone recommend a professional who could come and have a look at it in West Sussex (near Crawley)? Hopefully this isn't that uncommon - most houses have chimneys and bricks

Many thanks!

 

[Lime]

--- Have the chimney breast wall in the loft repointed

Not much to be gained really unless it is particularly bad and would allow fumes and smoke to escape. The water will not be getting in the brickwork here unless there is a leak in the roof.



--- Consider ripping all the plaster off the chimney breast in the bedroom and repointing the whole wall (even though I don't know if there's a problem with it)...

The plaster may have to come off once the water ingress has been stopped but pointing the chimney breast would not stop water seeping through.



--- Get a different chimney cowle to try to stop the water (is this even possible?)

Some cowls are better designed than others to stop rain falling directly down the chimney. However modern chimney pots are decidedly smaller in diameter than older ones so you would need to hunt out a suitable salvaged pot.



--- Consider getting the chimney relined (don't really want to do this if it's going to be really expensive - would it really be required?)

This may or may not solve the problem.




There are six basic ways plaster can become damp on a chimney breast.
1 Rain falling down the chimney and soaking the brickwork.
2 Water entering the flaunching (the mortar surrounding the chimney pot and holding it in) and soaking the brickwork.
3 Rain entering the bricks outside on the stack if the pointing is poor.
4 Rain entering the junction between the roof and the stack and running down the brickwork within the roof.
5 Condensation and lack of ventilation within a flue.
6 High humidity within a room causing condensation to form.

Often it is a combination of two or more of these things as in your case.

You need to open up and ventilate the sealed fireplace.

You need to have the chimney stack inspected (you can do this yourself using binoculars) to see if the pointing needs replacing. Sometimes it is discovered that the pointing has all but disappeared.

The flaunching and pot/pots need to be inspected for soundness. That does require climbing up to the pot/pots.

Although you have had the roof inspected it is quite possible for water to enter next to the stack in a way that is difficult to see. Perhaps in a heavy rain storm you should climb in the loft and take a close look at the junction between the underside of the roof and the stack.

You need to ensure that the wall covering (paint or paper) in the room allows water to evaporate too.