Close Un-used chimney

Hi Guys,

Our 1950's fibro house also has a large brick chimney. I believe that when we have sustained heavy rain the chimney is allowing small amounts of water into the house, specifically onto the gyprock walls. During lighter rain or short storms we don't seem to have a problem. I am about to renovate my kitchen so I would like to prevent this from happening, so I am looking for advice on closing off the top of the chimney.

The only opening in the chimney is the top part above the roof line through which smoke would have once been emitted. There were other openings down in the kitchen, specifically two small metal doors (perhaps 20cm square each) that appear to have been jammed shut for decades. There is no traditional "fireplace" as such, I believe it's sole use was as a stove.

Anyway, it sounds like a simple task to just close off the top of the chimney but some quick research seems to imply that it is not this simple (as is often the case). Apparently I need to allow air to continue to flow in order to avoid damp problems? We have a damp subfloor so this seems relevant to me.

Anyway, my plan is to use a small piece of fibro (equal to the external dimensions of the chimney) to cover the top of the chimney. In order to allow air flow to continue I intend to sit it atop four bricks (one at each corner), so air will continue to flow under the fibro and over the top of the chimney opening but rain will be largely blocked.

Does this sound like a good idea? I would have like to use a concrete slab (which I can see has been used on my neighbours chimneys) rather than the fibro but there is no way I am going to be able to lug one up on top of my roof which is quite steep.

Any comments or advice ?

Are you sure it is the chimney or the flashing around the chimney that is allowing the water to seep in ?

Stewie

Hi,

I had thought it was the flashing (which was in poor condition and had puled away from the brickwork) but I have slathered the whole lot with exterior grade silicone, but the problem persists.

Well, silicon is OK up to a point. If it was me I'd just replace the flashing to make sure.

Edit : The other option is to remove the chimney above the roof and then just extend the roof battens and the roofing over the hole.
That'll depend on whether you have a tiled or steel sheet roof too.

Stewie