PRIVATE RESIDENCE, DISS, NORFOLK
Project: Building Defect Survey
Client: Private Client
Services provided: Building Surveying
Contract value: Undisclosed
Daniel Connal Partnership was appointed to carry out a building pathology survey of a private dwelling in Diss.
The 3 bedroom end of terrace house was constructed in 2011. Its external walls are formed of a timber frame with hempcrete infill giving a textured render finish, with timber cladding to the head of the gable elevation. The pitched roof is covered with interlocking imitation-slate clay tiles. The owner had reported a number of issues with damp.
Hempcrete is a bio-composite breathable material used in construction as an alternative to traditional lime mixes.
Our survey revealed dampness and loss of the decorative finish above the first floor bedroom windows on the front elevation of the property. The damp coincided with an area constructed in a more traditional timber frame manner and where we would have expected to see a breather membrane and vapour control layer installed.
We also found the external walls of the living room on the ground floor to be damp at low level. The use of resistant multi-pro XS board was likely to be compromising the breathability of the hempcrete causing moisture retention. The use of a breathable woodwool board, such as Heraklith, would rectify the problem.
We observed no air bricks to the front or gable elevations resulting in a lack of ventilation to the sub-floor void below the ground floor. Lack of ventilation to the floor void can lead to a build up of moisture and, subsequently, damp. Installation of air bricks would ensure adequate ventilation.
Higher moisture levels were evident at all external wall openings, raising concerns about air-tightness and cold-bridging. We used a thermal camera to confirm this cold bridging and recommended consideration be given to revising window and door detailing to rectify the issue.
During our inspection we measured the relative humidity values in all rooms. Whilst within an acceptable range, these were slightly high and we recommended that the mechanical ventilation heat recovery system (MHVR) be serviced and adjusted as necessary to reduce the relative humidity to optimum levels.