Child Item

How to water-proof large chimney cap?

I have an old mid-century home with a large chimney that has a cap on it that is quite degraded and crumbled. We have had a mystery leak for some time and I am pretty sure it's getting in through the top, and slowly running down the walls into the house. I know that the ideal solution is to completely replace the chimney cap, however it's a bigger project that will trigger other works that I currently don't have the time or budget for.

I wanted to know if anyone has experience applying a sealant of some sort that might help in reducing ingress of water? I don't want to use anything that is an opaque grey or black rubber, as the cap is visible from the front of the house (we are on a steep block). I'm thinking of a pond or concrete sealant of some sort but not too sure if there are other better options.

If anyone has experience with this I would love to know.

Find more posts tagged with

Repairing

Plumbing

Accepted answers

All comments

EricL

Hello @Glyph

Thank you for sharing your question about your chimney cap. Because this involves a high temperature appliance, it’s important that any repair work is carried out by a professional chimney repair person to ensure safety and compliance. Any product used on your chimney must be fire and heat rated as ordinary sealants or paint will not be compatible. I wouldn’t want to risk giving advice that could be incorrect or potentially unsafe, so it’s best to avoid attempting any DIY repairs in this case. I propose obtaining a few quotes or getting one of the professionals to assess what a minimal repair will cost. This would possibly include either a patch or temporary cover of sorts that will stop the leak but still comply with fire safety regulations.

If you need further assistance, please let us know.

Eric

Glyph

Sorry I should mention this chimney is dormant it hasn't been used for 12 years. So I simply need a water proofing solution for now.

EricL

Hello @Glyph

Thank you for sharing that extra information about your chimney. If it is dormant and is no longer to be used or activated, I propose looking at using https://www.bunnings.com.au/dakaflash-300mm-x-1m-terracotta-lead-free-flashing_p0565649 . It can be cut into strips to patch unusual shapes and can be painted over especially if you are wanting to match your chimney colour so that it does not stand out. My best advice is to clean the surface of the chimney of rust and wash it down so that there is no residual dust or dirt on its surface before you apply the flashing.

Please note that this suggestion is given on the condition that the chimney will remain dormant and will no longer be used.

If you need further assistance, please let us know.

Eric

Glyph

Thanks Eric how would you fix this flashing to the actual chimney cap? It says self-adhesive but I'm not convinced it can adhere to a crumbling surface?

EricL

Hello @Glyph

The surface must be thoroughly clean before you attach the flashing to the cap. Any dirt, dust and debris or irregularity must be removed from the surface before you apply the flashing. It has a self-adhesive butyl backing that will adhere to almost any surface. You can use a tennis ball and roll it on its surface while pushing down to force the flashing to stick to the surface. There are other flashing products, but this one was terracotta coloured and thought it would be a close match to your brick colours.

Eric

Glyph

Ok thanks I will look into it. The chimney cap is grey concrete, so my hope was to be able to apply a seal of some sort over that and maintain the age and character. I can still use the flashing idea, and paint it grey, but the challenge is it will be very visible from the front of the house and will look like a repaired chimney cap - which I am trying to avoid.

EricL

Hello @Glyph

Just to add to the suggestions made, there is the https://www.bunnings.com.au/crommelin-4l-exterior-grade-brushable-waterproofer_p0961599 and https://www.bunnings.com.au/bastion-4l-exterior-waterproof-membrane_p0363842 which are brush on waterproofing agents. Both products are grey in colour.

Eric

Child Item