I carried out an interesting survey in Gloucestershire this June. The weather at the time of the inspection was warm and sunny. This proceeded several weeks of warm, relatively dry weather (which usually makes penetrating or rising dampness harder to find).
The property I was surveying originally started life as a public house. Part of the bar can still be seen within the living room. It fronts onto a busy main road. The property was most likely constructed circa 1600 is of solid Cotswold stone construction.
An extension has been constructed to the rear of the property and there is now a central valley to the roof between the original and extended part of the property.
Externally, the subject property had been recently redecorated, in what appears to be an impervious masonry paint. This was likely covering structural defects which may have recently been repaired. It also appears that repair works, and repointing have been carried out in a cement-based mortar. This is a big no-no.
Cotswold stone is a form of limestone formed of sedimentary rock. It is therefore porous by it’s very nature. The cement pointing is likely to cause damage to the surrounding masonry over time. Moisture becomes trapped in the masonry and when there are freezing conditions, the water content expands, which causes the face of the masonry to perish.
The external ground level to all elevations was significantly higher than the internal floor level, particularly to the rear and side of the property.
With the above issues in mind, you would not be surprised to learn that significant dampness was found to be present throughout the ground floor.
The rear wall of the property had been recently tanked and replastered. It also appeared that previous damp proofing work to the base of the wall to the front elevation has also been carried out. However, the front wall above the bottom 1-m was completely saturated, as were a number of the internal and boundary walls.
Properties of this age and built in this manner should be able to breathe. Due to poor maintenance works carried out over the years, the ability for the building to breathe has slowly been removed. Our recommendations were;
1. To remove all of the external paint which will be trapping moisture within the masonry and exasperating the rate at which it deteriorates.
2. We recommended that an experienced Stone Mason rakes the joints out to a depth of around twice the width of the mortar joints, and re-point the masonry with lime mortar, which should allow it to breathe.
3. Where feasible, we recommended that the ground levels are lowered by the installation of a boxed drain gully. This should help to reduce the likelihood of rising dampness, and at least give any damp proof course which may be in place a fighting chance.
4. Internally, we advised that at the ventilation throughout the property is significantly improved.
5. We recommended that the walls are re plastered using a lime-based plaster and decorated using a breathable paint.
The subject property was also affected by serious structural issues.
Significant distortion was noted to the property, particularly to the rear elevation, where the top of the wall is bulging outwards significantly. This is likely to be the result of roof spread, due to a combination of oversized rafters and replacement concrete roof tiles, which would be significantly heavier than the slates which would have originally been in place.
Roof spread occurs when the downward pressure of the weight of the roof starts pushing against the rafters enough that the structure itself begins to move either the roof starts moving downwards, or the walls start pushing outwards. This is a prolonged process but can cause severe damage to the integrity of a home.
We recommended that a Structural Engineer is appointed to compose a specification for the installation of additional restraint to both the walls and roof structure in order to prevent this movement from continuing to the point where the external wall needs to be completely rebuilt.
By Daniel Hickman.