Why Important
Penetration of water from an external source is often due to poor maintenance, allowing rain, melting snow or ice to enter.
What to look for
The most common signs are:
- Blocked or damaged gutters and downpipes, resulting in damp patches appearing after rain. External stonework may be stained and there may be signs of vegetative growth. A faulty internal conductor from a valley gutter may remain undetected for some time. For remedies, refer to Birkenhead Historic Home Guide for Gutters and Downpipes.[Link]
- Defective roof coverings, resulting in damp patches after rain or snow. The source of dampness may not always be apparent, since moisture often runs down the rafters and drips off at some distance from its point of entry. Cracked, loose or missing slates can usually be replaced, but sometimes, for example with a lead roof covering, it is preferable to replace a whole section rather than to patch and risk a repeat of the leak from an adjacent weak spot. For repairs, refer to Birkenhead Historic Home Guide for Roof Coverings. [Link]
- Defective flashings and soakers. For repairs, refer to Birkenhead Historic Home Guide for Flashings.[Link]
- Faulty stonework, open vertical joints or cracks in horizontal projections are liable to conduct water into the wall. Stone cills, cornices and string course are particularly vulnerable. For repairs refer to Birkenhead Historic Home Guide for Stone Repair.[Link]
- Faulty pointing to window frames and the absence of drips on timber cills. For repairs, refer to Birkenhead Historic Home Guide for Sash Windows. [Link]
When to look
The cause of penetrating dampness must be remedied as soon as it is diagnosed; severe occasional penetration is often less dangerous than a slow drip which may go undetected for years.
Once a leak has occurred or been found, it is essential to check all timbers for signs of decay.
The possibility of plaster ceilings collapsing some weeks (or even months) after severe water damage should not be forgotten.
How to fix
If the timbers are sound and well ventilated, they will dry out without further damage.
To be effective, damp-proofing must be thorough and must protect all floors and walls against penetrating moisture.