If your chimney is leaking, then you will need to repoint it. Repointing involves fixing the mortar joints that have crumbled away.
Some joints may have split, so you must also repair them. Other joints may have crumbled away, so you only need to repoint them.
If your roof is leaking, then there are several other causes for the leaking, and you may choose to leave the roof for a later date.
How to repoint a chimney
1. Step One
If your fireplace or flue is on the roof, it might not be easy to access. It would help if you moved furniture and put plastic sheeting down over the carpet or flooring. You can also use an old blanket as a drop cloth.
2. Step Two
Cover up any windows with newspapers or cardboard. If you are working in a room with a lot of furniture, then cover it up with plastic sheeting to protect it from brick dust and cement splashes.
3. Step Three
Clean out the fireplace and flue. Use a brush and vacuum to eliminate as much soot and dust as possible. Some soot will inevitably remain in the flue and is not a problem.
4. Step Four
Use a pair of pliers or a wire brush to remove any mortar still adhering to the bricks. Scrape around the edges of any mortar joints, taking off any loose mortar
5. Step Five
Flatten out any cracks in the mortar joints with a cold chisel, but do not hack at them with a heavy tool, as this might make it impossible for the new mortar to adhere properly to the bricks
6. Step Six
If repointing the joints, use a mortar rake or a pointed trowel to firm up the mortar joints between the bricks. Use as little mortar as possible, and try not to get any on the surface of the bricks.
7. Step Seven
Do not add too much water to your cement mix. It should be like a thick cake batter – too runny, and it will never set properly; too thick, and it won’t be easy to work with. If the mortar is too hard, then you can use a little water to help it become easier to handle
8. Step Eight
Sponge down the bricks with water while they are still wet. If they are too heavy to move comfortably by hand, use a trowel or pair of pliers to skim them off the mortar bed.
9. Step Nine
If you are repairing some of the brickwork around your fireplace or flue, use a dampened cloth to wash them gently, so they do not crack as you repoint them.
10. Step Ten
Build up the new joints with mortar similarly to the old ones. Firm up each layer of joint with a trowel or a mortar rake until you have reached the point that you have started again
11. Step Eleven
Remove any excess mortar by using a razor knife or electric sander to scrape it off from around the bricks.
If this is not possible, use a worn-down chisel to carefully scrape off the excess mortar from around the edges of each brick. Avoid pressing too hard, as this might crack the brick face.
12. Step Twelve
Once you have finished repointing, you can use a dampened cloth to wipe off any excess mortar. Once again, do not press hard on the bricks, or they might break.
13. Step Thirteen
Repair any splits or cracks in your joints with a small piece of patching compound. This can be applied with a brush, pushed into the crack, and left to set.
Alternatively, use a pair of pliers to push the patching compound into the cracks with a twisting action that makes it difficult to shift out of position.
14. Step Fourteen
Ensure you leave your repointing mortar for at least six hours before testing it for strength. If it is not strong enough, use a moistened finger to apply some water to the joint. If the mortar still does not set properly, use a dampened cloth and sponge in a little water.
15. Step Fifteen
If you are only repointing some of the joints in your chimney, you can apply a small amount of cement to as many as five or six bricks at once. Apply this with a brush, and take care not to get any on the surface of the bricks
Chimneys can be repointed easily, although you must ensure that the right mortar mix is used. Otherwise, it may not be set properly. It would help if you also covered the surrounding areas before you began.
Ask an experienced bricklayer or builder for some advice and assistance if you are unsure about the process or can not carry out the repairs yourself.
Repointing your chimney may seem daunting and difficult when tackling it for the first time. However, it is, in fact, a fairly straightforward task and is something that can be achieved by almost anyone who has basic DIY skills.