Find Roof Leak Near a Chimney

Roof leaks can sometimes be very difficult to find, locating the damp patch on a ceiling is the easy part but locating the source of the water penetration isn’t so simple. Leaks that are near a chimney can often be the most difficult to find.

If you are a competent DIYer then please do not spend too much time in your loft, the source of a roof leak can only be located from the outside, water tends to travel along tiles, timber and felt so finding the original source is tricky, especially when all you can see in a loft is the underside of roofing felt.

In most cases it will be because of a broken tile, you may find that the tile is hidden by a peice of lead.

Below you can a find list of typical places that produce leaks near a chimney. After 15 years of roofing this is the best checklist I can think of:

  • Check the lead around the base of the chimney, look for cracks or where it may have pulled out of the bricks.
  • Check that the tiles underneath the lead are not cracked or broken – you may need to lift the lead slightly.
  • Check condition of the ridge tiles near the chimney, remember water may travel some distance before entering the house.
  • The top of the chimney should be checked, install a cowl and replace any cracked cement.

Chimney Lead

The lead that is often located around the base of a chimney is the most common place for leaks to occur, small cracks may appear over time and occasionally the lead may pull out of the wall. Always check underneath the lead for cracked or broken tiles, these may not be visible until you lift the lead slightly.

Check The Top of The Chimney

The chimney itself should have a suitable cowl to keep out rainwater from the flue and also a flaunching of cement to protect the bricks.

The best chimney cowls are those manufactured by Colt Top, they are universal and can be used with any fuel. They are are also designed to keep out birds and encourage updraught.

Condensation

This is a problem with many disused chimneys that have been capped. The flue itself will retain some moisture and without adequate ventilation, damp and condensation may occur. Ideally, a disused chimney will have vents at the base (such as a wall vent) and also at the top (such a cowl). This creates a small amount of updraught, not enough to reduce the thermal efficiency of the property but enough to ventilate the chimney shaft and prevent condensation/damp.

Soakers

Some roofs have small pieces of lead or aluminium underneath each tile that is butted up to the side of a chimney, these (if they exist) must be checked, as they often slip and cause a leak.

Just lift up a tile that is adjacent to the chimney you should be able to locate a soaker if they have been installed, check that none have slipped. See diagram on section 5 of this pdf for more information – Wickes guide to chimney flashing and soakers.

Things to Avoid

If you are a homeowner that has just discovered a leak somewhere near a chimney, you may be tempted to start removing felt from the loft in an effort to locate the leak. Please don’t!

In 9 out of 10 cases the leak cannot be located from the loft. It is likely that the source of the leak is some distance away from where it enters the loft, so please either check the roof from the outside or if that is not a safe, then please call in a professional.

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