Approximately 15 years ago I had the fireplaces removed from my mid-terrace house. Whenever it rains I can hear the sound of internal drips which are particularly audible from the upstairs bedroom and livingroom directly below. There is no indication of a leak in the attic, however we have noticed damp patches are appearing on the ceilings of both rooms. What is the issue here and how can we resolve it.
As we have changed the heating regimes in our homes to centralised systems, the requirement for open fires in houses has declined and often is relegated to aesthetic use or replaced by a screen. This redundancy has led to many fireplaces being closed off completely.
The advantages of closing up a flue amongst others includes reduced draft and improved energy efficiency of central heating systems.
Care must be exercised to ensure there is sufficient ventilation remaining in the house to maintain healthy air quality and there are also other pitfalls such as the one you describe if the method of closing up the flue is not understood.
When solid fuel burns, the components of combustion rise up as smoke and some of this sticks inside the chimney as soot or tar as it cools down. Some of this material is left in a flue when it is closed up and it is impossible to remove it. Under the right conditions and because it is ‘hygroscopic’, this soot attracts water from moist air and this causes damp or dirty looking patches to appear inside the house often at places of weakness in the structure such as at floor or ceiling levels.
Provision of vents at each fireplace and above roof level maintains a draft in the flue and reduces the potential for soot to react to moisture in the air as well as helping maintain a healthy air quality in the house.
You don’t say if you capped the chimney at roof level as well as closing off the fireplace, if the pots remain and are still open to the elements then this is probably the source of your ‘drip’ during rainfall?
If the chimney was closed off at the roof then another potential is that the roof flashings and ‘soakers’ have become dislodged during that work allowing rain to penetrate the chimney and drip down inside.
As a mid-terrace property it is probable that the chimney is shared so you should discuss and agree with your neighbour how best to close off at roof level if that has not already been done. Your local building surveyor can assist to track down the problem and advise you appropriately.
Fergus Merriman is a member of the SCSI Building Surveying Professional Group