Damp patch on chimney breast

Damp patch on chimney breast

Monday 16th November 2020
Lea Streat BSc Hons

Structural building Survey November 2020

Location: Pinner, North West London

Issue: Birds nesting within chimney breasts of unused chimneys causing damp internally

Tayross Associates recently undertook a structural survey on a 1930's detached three-bed property.
Whilst conducting the initial walk around to get a feel for the property, one of the bedrooms had a round wet patch which could be seen to the centre of the chimney breast. We noted on our external inspection that the chimney pot, which appeared to be of compressed asbestos cement, had no cowl sitting on top of it.
The property had been sitting empty for a while and the chimneys were not being regularly used. This has allowed birds to drop twigs down into the chimney breast and nest within. When it rains the trapped twigs become saturated and the brickwork soaks up the trapped moisture, which seeps through to the other side of the wall.
Solution - If the property is in use regularly, using your chimney will deter birds from nesting within. However, if the property is not being used regularly, placing a cowl on the top of your chimney pot will stop birds from being able to nest.
This chimney breast will need to be cleaned using a chimney sweep to knock out the birds' nest. A cowl should be placed on top of the chimney pot. The chimney breast will then need to be properly ventilated using hit and miss vents to allow good airflow to dry out the bricks and plaster.