Resolving Damp Issues

Damp is the most common issue we come across, and it can make living in an historic building a cold and miserable experience. Solving damp in period properties requires a thorough understanding of old buildings, the wide variety of materials used in them and the way all of these work, both independently and collectively.

Causes

Damp problems can be caused by something as simple as a blocked downpipe or a missing tile. However, they can also be a sign of a longer-term issue. Moisture can be trapped within a masonry wall by cement render or pointing outside, and/or gypsum plaster inside. Sometimes the external ground levels are higher than the internal floors, which creates severe damp in the ground floor rooms. It is essential to understand and address the cause of the damp issues, both for the structure of the building and for your own health, as mould growth in damp properties can be very harmful.

Damp-proofing Historic Buildings

It is worth mentioning here that regardless of what some people (who do not specialise in older properties) may tell you, it is impossible for a damp proof course to work in an old building. 

This is because the very nature of an older property is that it has an intimate relationship with its environment, including moisture, whereas modern techniques (including a damp proof course) are quite the opposite, being focused on sealing and isolation. Old properties are specifically designed to allow moisture to pass through them and any attempt at introducing a damp barrier of any kind only increases the probability of trapping damp in the first place.

Water-proofing sealants should not be used on period properties even if they are advertised as being ‘breathable’ as they not only can trap moisture within the walls, but once used, the surface of the stone or brick is rendered permanently impermeable.

Solutions for Damp Issues

Replacing cement renders and pointing with lime will allow the walls to dry out over time, although it can take months or even years to dry completely. Removing paints made from plastic, non-permeable materials from the internal and external walls of a building can also help the walls to dry. Meanwhile, installing ‘French Drains’ can also alleviate water pressure on the base of the walls, creating a cavity into which the water can drain.

Wanstrow – Resolving Damp Issues

Here we removed cement pointing and re-pointed in lime, with lime render and limewash over. We recessed the windows, and reinstalled them with proper sills with drips. Inside, we removed wet gypsum plaster and replaced it with lime.

Before work started.
The modern windows had been installed virtually flush with the exterior wall, and did not provide adequate protection against driving rain.
The pointing was cracked and failed in places.
Poor installation enabled damp to penetrate the wall.
The interior plaster showed signs of damp.
The windows are recessed correctly and a stone window sill with drip has been installed.
Drip detail – this is very important so that rainwater is cast away when it hits the drip and can’t track back to the wall.
Traditional 3-coat lime plaster – this is the 2nd (float) coat.
The walls are ‘dubbed out’ with lime before applying render.
Limewash in the process of drying.
Lime render in progress.