Avoidance of Leaking Buildings

Many of the building techniques leading to problems with waterproofing homes have been addressed and incorrect building processes should be picked up at inspections, however, there are definitely things you, as the homeowner, can be aware of:

• Beware of decks enclosed by solid walls with a lack of drainage and perhaps a handrail attached to the top of the top of the wall – water cannot drain and the weather proofing skin may have been pierced by the handrails.
• Wall cladding materials finished hard down onto a deck surface or paving or paths: the cladding will absorb water from the surface it’s finished onto.
• Wall cladding extends below ground level or landscaping materials, including mulch, are built up against the wall – materials that are continuously damp will quickly deteriorate.
• Waterproof decks that are constructed to the same height as the internal floor, with no fall for drainage, compounded by an outlet that can get blocked.
• Suspended timber floors need space below the floor for ventilation to remove moisture evaporating from the ground.
• Leaving the underside of profiled steel roofing exposed at overhangs or eaves – this will void your manufacturer’s warranty.
• Using sealant instead of properly designed flashings.
• Make sure head and sill flashings are installed over windows and joinery.
• Parapet walls need cap flashings or a slope to drain water.
• Kick-outs or diverters to apron flashings where roofs abut a wall surface are necessary to ensure that water flows into the gutter and down inside walls.
• Design features that penetrate the cladding, such as projecting timber beams or handrails, are almost impossible to effectively waterproof.
• Monolithic claddings and tiled finishes require movement control joints that allow building movement to occur without cracking.
• Eaves and drip edges at the base of claddings and above windows are strongly recommended.
• Ensure adequate detailing on junctions between materials.
• Check the difference in levels between the surface outside and floor inside and/or that there is good drainage – without these the building may well fail to meet the performance requirements of the Building Code in regard to external moisture provisions.

Information supplied courtesy of BRANZ

Websites to visit for more information:

www.weathertight.org.nz
Weathertight Homes Resolution Service (WHRS) www.weathertightness.govt.nz