Common problems with roofing and cladding include corrosion, lack of underlay, cracking in masonry, rising damp, and corrosion.
It was common for the wall and roof cladding of villas to be installed without the use of a building paper or underlay. Many villas are likely to have been reroofed without the roof underlay being installed.
Options are to:
- when replacing roofing, install underlay
- for existing roofing, install underlay to the underside of the rafters – while not ideal, it will act as a temporary condensation absorber and restrict air flow into the roof (Remember that a 25 mm gap is required between a flexible roof underlay and the insulation.)
- for walls where access to the back of cladding is possible, install underlay folded into the framing cavities.
Where there are cracks in brick masonry walls, foundations or chimneys, the first task is to determine the cause of the cracking and if the crack is likely to get wider.
Settlement of the ground over time
With settlement, the key question is to determine if it is still occurring. This can be done by monitoring the width of the crack. If static, then the decision is whether to accept the movement that has occurred and work around it or attempt to underpin the building.
Past earthquake damage
Cracked joints may able to be repointed, and it is possible to replace bricks that are cracked. If the crack is still widening or a repair is proposed, specialist engineering advice and design is required.
Shrinkage and swelling in expansive clays
Expansive clays will always swell and shrink in response to the amount of rainfall so it is likely that these cracks will open and close regularly. While joints can be repointed, they may crack again as the clay moves.
Corrosion of reinforcing in lintel beams
Corrosion of reinforcing usually means some significant damage, which will need to assessed by an engineer. Where the damage is minor such as a small amount of spalling to the lintel, a specialist epoxy repair may be possible. Corrosion that has also resulted in cracking of the brickwork will generally require an engineered solution.
Moisture being drawn up through brickwork can be a problem with chimneys (almost all villas had one, and many had two) and within the walls of villas constructed with brick.
With chimneys, the problem of the moisture can be avoided by inserting a DPC between any timber and the brickwork – it was common for original timber to be in contact with the brick, and this timber is commonly rotted and in need of replacement with new H3.2 treated material.
For brick wall construction, the problem is more difficult to remedy as the rising moisture occurs because the DPC, if inserted originally, has failed over time. A sign of moisture being present is efflorescence on the walls and/or paint bubbling from the surface. Repair is difficult because inserting a DPC into an existing wall requires substantial and progressive removal (and replacement) of bricks. One option that may give some success is the application of a proprietary waterproofing system to the face of the bricks.
Corrosion of a metal component such as roof cladding, fixings, flashing or accessories can be caused by:
- moisture plus one of more of salt spray, dirt or hydrogen sulphide from coal-burning fires or geothermal activity
- contact between different metals in a damp environment (such as galvanised steel, copper, zinc/aluminium alloy-coated steel)
- contact or run-off from copper-based timber treatments over steel.
Villas close to the sea are likely to be affected by salt or chloride contaminants. Areas most likely to be affected are the subfloor, cladding nails, roof and window flashings and external pressed metal panels.
Corrosion may appear as the familiar red rust or as a white discolouration on the surface of materials containing zinc, which is called white rust.
Rust can also chemically attack timber around an affected fastener – something known as ‘nail sickness’ (Figure 1). The dark staining around nails in old floorboards may be unsightly and indicate a slightly weakened part of the timber, but is not generally a structural risk.
Flashings, fixings and accessories badly affected by rust (with a pitted surface or pinholes) should be replaced. The risk of future corrosion can be reduced by painting steel, specifying factory-coated steel and using hot-dip galvanised steel or stainless steel fixings and brackets.
Where corrosion on mild steel is only on the surface and can be removed by sanding, the steps are:
- sand with grit paper to expose shiny metal
- prime with a zinc-rich primer
- apply a solvent-borne metal primer
- apply two finish coats.