In our climate, the primary requirement for a building is to prevent the penetration of moisture into its envelope. The envelope must shed rainwater away from the building like a tent.
Penetrating dampness in a house can lead to dry and wet rot in structural timbers, woodworm infestations, and an unhealthy atmosphere and mould growth.
Sign of long-term penetrating damp
Which will lead to extensive structural timber decay
How the climate affects a building
The southwesterly building walls and roofs are most affected by rainwater. It can damage the fabric of the roof and chimneys. It carries leaves, which block gutters and downpipes and drive rain into cracks in the masonry and gaps around windows and doors. On the lee side of the building, the pressure draws moisture into the building. In urban areas, the effects of driven rain are variable. In high-rise buildings, wind strengths and directions may change with height. By the coast, onshore winds have an additional impact due to the salt carried in the air (salt damp). This has significant effects on buildings constructed using lime mortar.
Ice, frost, and snow (water in its solid state) can damage masonry pointing and cause spalling on brick faces, leaving them porous and more susceptible to rapid decay. Any flashings embedded in pointing attacked by frost can become loose and allow water penetration. The frost action (combined with salts) on one side of a chimney over time may cause the joints in the stone/brickwork to open wider, causing the chimney to lean.
The sun’s heat can blister flat roof-felting fabric, leading to defects, rainwater penetration, and insulation failure. Timber windows, door frames, etc., shrink away from the masonry overstretch sealants, allowing rain penetration.
Some effects on a building’s envelope
Typical defects include blocked downpipes, guttering with an incorrect fall or a belly creating overspill, and guttering standing beyond the drip line of tiles or slates.
This results in damp patches and, in some cases, mould inside buildings. This is often caused by water from faulty rainwater goods, roof leaks, and defective masonry. These factors are responsible for most wood rot in buildings, and all timbers abutting the affected walls must be investigated.
OG-style cast-iron wall head gutters are prone to hidden leaks and are a significant cause of structural timber decay.
The cast iron gutters are susceptible to rust as they age and become vulnerable if they are not regularly maintained with fresh paint. Protecting your investment is essential to addressing this issue proactively before it becomes a costly problem. Additionally, regular maintenance will extend the lifespan of your gutters, ultimately saving you time and money.
Cast iron rainwater downpipes rust and crack over time.
Frost can split rainwater downpipes.
Broken or missing rainwater downpipe shoes can cause drainage problems. Instead of directing water away from the building, it may flow towards the wall.
Valley and parapet gutters pose serious risks of wood rot if not maintained and free from leaks; clogged areas may also allow water to escape the flashings and seep into the building’s masonry core, causing dry rot in timber.
Additionally, lead used in valleys and gutters can deteriorate over time due to pollution and acidic rain.