Air brick / Vent for sealed chimney question

nobile

Hi. In one of my ground floor rooms, the chimney has been totally sealed/bricked up. We have had a few damp patches on one side of the chimney wall.

After painting we noticed that the paint become dry/flaky...that was a few years ago

I had the chimney capped so no rain etc falling through now but the damp issue stated above still there....contained & not getting worse

There is NO vent or air brick in the chimney - I know there should be one!

My question is as a first response, would drilling a few holes in the chimney wall & covering with a vent suffice OR does there need to be an air brick fitted?

Or none of the above?

Many thanks

Davesnave

There is nothing magical about an air brick; it just ensures there's enough air entering relative to the area it takes up. If you make a good, almost brick -sized hole and cover with a vent that will do much the same job.

But what's behind the chimney wall at that point? Is it a neighbour's house or the great outdoors? If outdoors, look for causes of damp in things like raised garden levels, or a leaky downpipe, drain, or soak away.

Apodemus

...and even an adequately vented but unused chimney can be damp - the residue of all the coal and wood burned in the fire is hygroscopic and absorbs moisture from the atmosphere, which can lead to damp patches in the adjacent wall.

nobile

Davesnave wrote: »

There is nothing magical about an air brick; it just ensures there's enough air entering relative to the area it takes up. If you make a good, almost brick -sized hole and cover with a vent that will do much the same job.

But what's behind the chimney wall at that point? Is it a neighbour's house or the great outdoors? If outdoors, look for causes of damp in things like raised garden levels, or a leaky downpipe, drain, or soak away.

Its a terraced house with neighbour on other side. They have no damp patches etc.

illusionek

When I bought my current house I was advised by my surveyor not to makes any vents inside as it may cause damp.

Davesnave

illusionek wrote: »

When I bought my current house I was advised by my surveyor not to makes any vents inside as it may cause damp.

I can't see how ventilating a chimney could cause dampness, unless the air in the house itself was laden with moisture for some reason.

Warm, damp air condensing on cold walls? Seems odd.

People sometimes have problems when they stop using the chimneys on older houses.

nobile

Hi guys. Me again

I've decided to install a vent in the chimney. Would drilling 4 or 5 holes (16mm) about 20-30cm above the skirting suffice, and then cover with plastic vent cover with fly guard?

I know an airbrick would be a better option but I imagine I'd have to call someone out...then we are looking at a fair bit of cash.

Thanks

FreeBear

Four 16mm holes will be more than enough. Saves having to chip away at the plaster to find the mortar joints between the bricks.

An air brick isn't that difficult to fit once you know where the mortar joints are. Use a long drill bit and drill holes all round the mortar. Then with a hammer & chisel, break up the brick & mortar. Allow a decent gap all round the air brick & surrounding brickwork, and pack the space with a fairly weak cement/sand mix. Probably a mornings work compared to 20 minutes to drill four 16mm holes.

nobile

FreeBear wrote: »

Four 16mm holes will be more than enough. Saves having to chip away at the plaster to find the mortar joints between the bricks.

An air brick isn't that difficult to fit once you know where the mortar joints are. Use a long drill bit and drill holes all round the mortar. Then with a hammer & chisel, break up the brick & mortar. Allow a decent gap all round the air brick & surrounding brickwork, and pack the space with a fairly weak cement/sand mix. Probably a mornings work compared to 20 minutes to drill four 16mm holes.

How much would such a job cost if I got someone in (an approx figure if you would know?)

FreeBear

Very rough guess... Including materials, probably around £150-200 (seems to be the typical day rate).