As the majority of low-rise residential buildings are constructed using traditional platform frame construction, moisture that penetrates the cladding to the interior wall cavity can cause significant damage to the performance, finishes and structure of a building. How can I control rain penetration? Bear in mind also that tarpaulin can damage thatch that could often otherwise be repaired, despite pressure frequently for complete renewal. Douglas Kent, SPAB Technical Secretary, explains. Roofs renewed with inadequate eaves overhangs or oversailing verges should be extended if jeopardising earth or timber-framed walls. Bear in mind also that tarpaulin can damage thatch that could often otherwise be repaired, despite pressure frequently for complete renewal.
Partial rain penetration or the wetting of the rain screen materials can be minimized by reducing the surface porosity and absorptivity or by control of the forces necessary to produce it. Partial water penetration of a wall by capillarity is difficult to overcome, but complete penetration can be controlled by introducing a discontinuity or air gap in the capillary, the joint, or the wall. Rain Penetration and its Control. Figure 5B: Air Pressure Differences. Provided the air barrier does not get wet, minor air leakage through it will not be accompanied by rain penetration.
Although there may be problems regarding adequate ties and support of the rain screen when this principle is applied to the total wall covering, it should be noted that the exterior cladding is relieved of much of the normal wind load. Several conditions can agitate the problem by creating higher levels of interior moisture and pressure. Bear in mind also that tarpaulin can damage thatch that could often otherwise be repaired, despite pressure frequently for complete renewal. The solution in Figure 2b, shows how a labyrinth shaped opening interrupts the flow of water.
They are just as likely to indicate a leak higher up, as damp descending through the core of a wall will pond when it reaches the damp course. Avoid, though, tanking, plastic-based paints and colourless water-repellent treatments on old masonry, except in certain circumstances below ground. Old buildings need to breathe. The society operates a technical helpline , produces advisory publications and runs various courses. For example, replacing cleft shingles with the same, rather than sawn ones, will ensure both a close visual match and better resistance against rain penetration because the surface fibres suffer less disruption, with the grain tending to shed water quicker. Sometimes a compromise may be possible, perhaps just by removing the render at the base of walls or hollow-sounding patches where localised detachment has occurred.