It is crucial to keep chimneys in good order, especially in older properties. With the widespread usage of central heating and rarity of log fires, many chimneys are at present an unnecessary addition to your property. A component of a stack could be prone to fail in high winds and other inclement weather, which might well lead to untold damage to property (or individuals) below.
Never try any repairs to chimneys unless the stack is little and easy to reach from the roof ladder or if you’ve hired correct chimney scaffolding.
Because chimney stacks are in a really exposed place, it’s common for the pointing between the bricks to crumble away. This might lead to dampness and also make the heap unstable. Damaged joints will need to be re pointed:
First rake out the old mortar to a depth of about 20mm and lightly wet the points. A garden sprayer is ideal for this. Then press fresh mortar in position and smooth it off at a small downward angle. The mortar should contain one-part cement to five parts sharp sand, with a little bit of PVA adhesive added to enrich its workability and adhesion.
An added vulnerable place is the mortar (known as flaunching) round the chimney pots. Supposing that there are cracks however, the pots themselves are still held securely in place you can fill them by injecting nonsetting mastic. Use one-part cement to four parts sharp sand, once again with just a little PVA adhesive. Distribute the mortar around the pots, building it up around the foundation and smoothing it so that it slopes down to the edges of the stack. This may permit any rainwater to drain off immediately.
Cracked chimney pots can occasionally be fixed with silicone mastic; otherwise they must be replaced. In the event you’ve got an old house you may manage to have acceptable pots from a demolition contractor or architectural salvage yard. To match the new pot, chip away the old flaunching and replace it with new mortar, as described above.
When the flues are no longer used, you can to suit ventilator caps for the pots to avoid rain getting in. Instead, you can to eliminate the pots and make the flues rainproof by bedclothes airbricks around the sides at the top and laying paving slabs within the flues to throw rainwater free from the stack. The airbricks ensure a gentle supply of air to the flues to keep them dry.
Back gutters and metal flashings could also be a source of moist issues around chimney stacks.
Once repairs to the chimney stack have been completed, this is a wonderful idea to paint the brickwork and the flaunching with silicone water-repellent sealer to safeguard against freeze damage and prevent rain penetration. The sealer dries colourless and doesn’t influence the look of the stack.