Dampness on Chimney breast

[jebby]

We live in a detached 2 storey 1906 brick built (tiled roof) house. The fireplace contains a gas living flame appliance.The chimney section protruding above the roof has been removed (before our time) and a flue installed . The flue section (which does not extend the length of the chimney)was recently replaced as we gather it did not satisfy regulations (being not to a sufficient height above the roof). .Since then we have had recurring problems with dampness in the chimney breast in the first floor bedroom.

We have had 3 contractors to try and resolve the issue. Tiles have been reset around the flue and the join (around the flue) sealed . In September last year the contractor decided to cement around the join (between the flue and the roof) and this has worked (with the dampness disappearing virtually immediately )until this August when the problem has recurred. There is a cowel with mesh sides on top of the flue .The same contractor thinks there may be water coming through the mesh sides on heavy driving rain. Although we don't discount this entirely as a potential contributory factor (the cowel was fitted by a gas engineer) we consider that there may well be a need to re cement the join (but this only seems to be a temporary solution) . We have made further enquires about the cowel and are given to understand that the one we have installed is correct. Is it however possible to use a cowel with side vents (but no mesh sides) for the gas fire and can anyone consider what else possibly we should do please?

 

[joe-90]

You are chasing shadows.

Look at this logically:

There are millions of houses out there with open chimneys that have not the slightest issue with damp.

Therefore logic should tell you that a tiny gap around a cowl etc isn't going to make any difference whatsoever.

This mean you must look elsewhere for the problem.

The most likely cause is that you have a difficult chimney and the gas fitters couldn't get the flue liner in so they just 'top and tailed' it. Put as much in from below as they could and then stuck a cowl on the chimney.
Either that or they damaged it during installation.

The damp you are experiencing is the flue gasses condensing on the inside of your chimney breast and permeating the bricks.

Take a look around the suburbs where you see a brick chimney on the outside end of a semi or terrace and you'll often see a clear line of damp up the chimney.

As Sherlock Holmes used to say:

Eliminate the impossible, and whatever remains, however improbable - must be the truth.

 

[catlad]

cement will not stick to aluminium for very long if you are convinced thats were the water is coming in then you can try a thick roofing paint called acropol about £50 for a 5ltr tin.