Damp patch on kitchen wall

Leif

When I had my kitchen redone, there was an old floor standing Potterton boiler with a flue that went into the wall. Anyway, the boiler was removed, and the hole in the wall filled with breeze block, then plastered over. A year later and a damp brown patch appeared. Clearly the hole in the wall was the opening to the gas flue (I have a gas flue, and a fireplace flue), and blocking it prevented a through draught from drying it out, so damp builds up, and breeze block being porous, the damp seeps through. What can I do?

I tried painting with Zinsser 123, not a cure I know, but I hoped it would work. Now it has reappeared, along with some fine cracks. The latter are easy to cure, a bit of paint hides them. It is possible that the patch appeared beneath the Zinsser 123 treated area. So repainting over a wide area might hide it. Or should I put in a small vent? In which case what kind?

The alternative is to hang a clock over the patch, as it is only 5" wide by 1" tall. It's arc shaped for some reason.

It does annoy me that builders are more interested in getting paid for work, than giving proper advice.

albyota

Hi leif, when the boiler was removed, was the entire flue removed too? Was it just going straight through the wall or did the flue terminate at a higher level, i.e at roof level? as you describe arc shaped I would suspect that the flue is still there in which case rain could be getting in and collecting behind the block work? Although after a year, with the rain we had last year, I'd have expected much more than a damp patch......

Leif

Hello albyota, yes there is a gas flue still in place, with an opening at the top of the chimney stack. and a cowl with nose shaped openings around its side. So yes, water is getting into the flue via the cowl, but due to the lack of a draught, it does not dry out quickly enough, and some seeps through the breeeze block in the kitchen and onto the wall surface.

I suppose an alternative to adding a vent in the kitchen is to block the flue at the top, perhaps in the summer when the flue is dry, perhaps using a balloon, or some such device. Now I think about it, this might be the best option, if there are no drawbacks.

albyota

Leif, hindsight is a wonderful thing, if it were my house, I would have had the flue completely removed and had the wall and roof? Reinstated. However, you are now where you are... I suspect it would be too disruptive / costly to remove the flue now, I would,therefore, depending on how easy it is to get to, cap off the flue terminal by riveting a cone on to it so no rain can get in.

Al

Leif

Hello albyota, what you do not know is that there are two flues in the chimney, one for the gas boiler and one for the open fireplace. That is standard for the houses on my 'estate' for want of a better word. I opened out the fireplace and had a wood stove installed, so the chimney is a permanent fixture now. Do you have any knowledge about how to block the flue at the top? I am scared of heights, but I live in a bungalow with a gently sloping roof, so even I should be able to clamber onto the roof, and access the chimney. Goodness knows how the cowl comes off.

albyota

Leif, I assume the flues are actually separated right to the top, I.e. they can be identified as gas and stove flues at the chimney stack?, if you are going to attempt to investigate, be safe, hire a proper roof ladder, and have someone foot the main ladder. Alternatively, contact a local Hetas installer to cap it off for you, wouldn't have thought it would cost too much, rather than falling off and costing more than an arm and a leg....hip.....wrists etc.
Usually using a 6mm steel drill bit in a battery driver to drill out the rivets, although you won't know how it has been fitted until you get to inspect it.

Be careful.

Leif

albyota, yes safety is of concern, however I have a flat roofed garage and connecting porch meaning I can easily get on the porch roof, and then climb onto the roof with little risk. I am not someone to take risks. Also, my neighbour is a marvel, he used to do stuff on his roof (as well as rewire his house, install his kitchen, and so on) until arthritis meant he could no longer clamber about, so I can ask his advice. Cheers.