Chimney has stack of problems

There are chimney stacks on the roof slopes of this London home.

The mortar joints are beginning to erode and some future re-pointing will be required.

Due to an unsuitable vantage point, we were unable to inspect the haunching on the chimney.

The chimney pots appear to be in reasonable condition. As and when any works to the chimneys are carried out we would strongly urge that the cement pointing around the chimneys be checked.

Any cracked or severely spalled and damaged pots replaced and the cement appropriately angled to deflect all rainwater away from the centre of the chimney stack.

When chimneys are constructed they are required to be provided with a damp-proof course to prevent water being drawn through the brick/block work and into the construction below.

Where the chimney in centrally provided within the roof there is usually ample space within the roof void for the construction to dry out but where on the flank wall if the damp-proof course has been omitted, it can lead to dampness internally.

Unfortunately, without the aid of long ladders etc it is often not possible to ascertain whether a damp-proof course has been provided.

At the time of our inspection there was no obvious difficulty in this respect.

The junctions between the roof slopes and chimney stack are generally formed with lead flashings. These are satisfactory and seen to be watertight, however, we noted localised missing sections which will require re-dressing tight to the roof to ensure a permanent and watertight joint.

Chimney stacks very often bulge and distort as a result of natural weathering caused by wind-driven rain, sulphate attack and also attacks by condensation and the products of combustion (soot and salts etc). Such problems are very often accentuated by lack of a proper flue lining system.

There is no evidence of this defect on the chimney stack.

Post Author: Frances Traynor