Damp on chimney in bedroom... condensation?

[Lago Jardin]

Hi I live in Spain but still have my house in Leeds. There is an external chimney which runs from the kitchen (the old fireplace has been bricked up) through a bedroom to the roof. Before I bought the house it was capped below the roof tiles. In the bedroom I have quite sever damp, following the line of the chimney(on the flat wall as the chimney is external). This does not show in the kitchen which is below the bedroom. I am pretty sure no water is getting in either through the wall into the chimney or through the top (it is well sealed). There is an inspection point into the chimney about 5 foot above ground level on the outside (now covered with a vent). I have put a small vent in the bedroom directly into the chimney.I thought the problem might be condensation which is why I put in the vents. The house is now empty and without heating the problem has become much worse. I have a tenant moving in very soon.

My Agent for the house asked a local builder to call and he seemed to advise the opposite to what I did...to totally brick up all vents. I always understood that u need an air circulation within the chimney.

So do I need more ventilation or none???

Any help would be much appreciated

Thank you

Nigel Smith Torrevieja Alicante Spain

NB

Thanks for all the help with my consumer unit wiring in Spain posted about

10 days ago

[Christian McArdle]

Well, loads of ventilation isn't working, so you could try having none.

If there is already an external vent, I would be inclined not to have an internal one. Ensure that the design of the external vent doesn't encourage water to penetrate inwards.

Also, check the capping at the top, you may be mistaken about its integrity.

Christian.

[stuart noble]

I think the rule is that if the chimney is capped (and sealed) you have no vents at all. If it just has a ridge tile or something over the top, you should have vents. That said, I still get a bit of damp on internal breasts due, I think, to the single course of brick between the inside of the chimney and the elements. Not something you have to worry about down your way I hope. Isn't Alicante supposed to have the best climate in Europe? Beats Malaga by a short head IIRC.

[Lago Jardin]

Hi

A little extra info...

When I first moved in the house there were no vents at all and the problem was there. The chimney is well sealed at the top (with slate and mortar) under the roof tiles. I wouldn't say that I have vented it with massive vents, just small ones. Since I put the very small vent high up on the outside of the chimney a small drier patch has appeared in the bedroom on the same level as the new vent but it hasn't spread out. As I've a tenant coming in I've got to rely on the Agent getting a builder in as I'm a 1000 miles away. I just don't want them getting it wrong!!!

Question is...do I enlarge it....or seal them all up??

Yer Torrevieja is supposed to have best climate but guess what...its raining heavily today after a pretty wet Spring!!!!! LOL

Thanks

Nigel

"stuart noble" supposed to have the best climate in Europe? Beats Malaga by a short head

[Andrew Gabriel]

You need a vent at the top and bottom of each flue, so air flows through them and allows moisture which comes through the brickwork to dry out (and water which comes down the pot if not capped off).

I recently found the plaster all blown on a chimney breast where the fireplace had been bricked up. A vent had been left at the bottom but subsequently wall-papered over. The pot had been removed from the top (was loose) and capped with a slate (no ventilation). As the chimney started getting wet, the gypsum plaster came away from the brickwork and then stayed remarkably dry. I noticed when stripping paper that the whole chimny breast would move if you pressed on it -- rather worrying;-) but this turned out to be just the plaster. I removed the plaster (pretty much came off in one piece, floor to 2/3rds way to ceiling). The brickwork behind was soaking wet, and has taken about 3 months to dry out with the fireplace opened up. It had probably been blocked off incorrectly for at least 20 years.

I have installed a vent at the base of the flue (to the outside) and another at the top (to the loft, as I can't get the the outside without scaffolding). The fireplace has been opened out to the room as a feature but sealed off from the flue.

[Hugh]

hi Nigel, might bump into you sometime - as I'm buying a property for refurbishment not too far from you in spain! Back to Leeds - have you ruled out all other sources of damp other than condensation? Is a gutter overflowing and running down the wall? Or a roof problem? Is the pointing in sound condition - could driving rain penetrate the brickwork? Looking at the brickwork outside may give a clue. If it's a victorian house - make sure there's no lead pipes buried in the wall just under the bedroom floor and leaking water from a tiny 'pinhole'. If there's a bathroom close by, it's a possibility. Hope that helps Hugh

[Lago Jardin]

Hi Hugh

The outside is brickwork covered with render and recently painted. Looks totally sound. The new external air brick at the top is only small, because of the height and only using ladders we could only drill holes thru with a long bit. The plumbing is all new copper...no pipes anywhere near the problem. New square section plastic guttering which again seems OK. There are 6 Tudor style detached in the Crescent. Others with similar capped chimneys seem to have the same problem even after the attention of builders!! That's what worries me. You see why I lean towards the condensation theory??

I'm inclined to take Andrew's view at the moment but welcome any ideas so that I know what to let the Agent actually do. They just want to send anybody and spend my money!!

Thanks for replying and thanks to Andrew, Stuart, & Christian too for their suggestions.

Nigel

[Al]

Was there a slow burning solid fuel stove or range originally in the kitchen venting into the chimney? If so it may be that acidic flue gases condensed in the upper part of the chimney and created a hygroscopic sulphate that absorbs moisture from the atmosphere and causes a growing damp patch. Does the damp patch grow black mould on it? If not this is an indication that the damp may be slightly acidic. I believe that sealing the plaster may be a possible cure, but the certain way is to replace the plaster. I have a similar problem. The flue is ventilated top and bottom but I think that this might have made the problem worse. Maybe sealing the flue is the answer.

hth

Al