Every year people suffer injury when chimney stacks collapse. It doesn’t take a serious event such as an earthquake to make it topple; it is more likely that the elements cause damage over many years and strong winds push it over.
There is a lot of weight in a chimney stack; sometimes several tons, so the damage is extensive. If it should collapse onto the roof, it will snap the structural timbers and fall straight through into the house. It might kill anyone who is in the way as it drops.
Damage to the chimney should be identified and dealt with early so that it will never undergo a catastrophic failure. for the complete novice, here is how to inspect and repair your chimney before the next storm comes along.
Basic inspection is simple. Get a good pair of binoculars and move to a position where you have an uninterrupted view of the chimney. The further away you are, the more difficult it will be to hold the binoculars steady when you zoom. If that is the case, mount them on a tripod. The tripod is available for less than ten pounds in shops, and it does a marvelous job. Look for cracks in the chimney stack; faults will be obvious. Then turn your attention to the mortar courses. Compare them to those in the walls of your house to see if the mortar has been worn away by the elements. That is a common fault with the brickwork. Don’t be alarmed by it at this stage. Inspect the lead flashing where the roof meets the stack; does the joint look clean or is there moss growing in it? If something is growing there, it could show a problem with the seal. Check the mortar around the chimney pot. If there are signs that some of it is loose or missing, you must repair it. Finally, use a plumb line at arms length to see if the chimney is leaning. If it is, there might be a problem with the structure or subsidence.
The first stage to repair the chimney is to get safe access. Ideally you will be able to use a ‘cherry picker’ which is a truck that has a lift on the back of it. Most people will use a ladder or scaffold. If you are using ladders, make sure to tie them off and make them secure.
Most of the repairs involve replacing old mortar. Use a mortar mix calculator to determine the quantity that you need. Before you point the chimney, remove the crumbling mortar. If you find it is crumbly all the way through, stop work immediately. The damage is too severe, the stack must be taken apart and rebuilt. If you can, put new mortar in the courses and refit the chimney pot. Clean the joint where the flashing meets the brickwork if necessary and use a tube of rubber sealer to fill any gaps and make it watertight again.
As you can see, it isn’t complicated to repair your chimney, so inspect it every year and do the little jobs as they occur. It will outlast you if you take care of it.