To the layperson, a 30mm shortfall in the length of a roof sheet may not seem like much. To an expert, it’s a key ingredient in causing moisture damage that could cost thousands.
Homeowner Steve Jackson renovated his 60s Castlecrag home in Sydney about 2 years ago. At the time, his builder installed a totally new roof. Soon afterwards Steve noticed that moisture was dropping down between the fascia and the back of the gutter, onto to the paving around the pool below. He also noticed that there was mould growing on the underside of the soffit - in the lining about 400mm in from the fascia
He called the builder back three times to try and find the problem. The builder told him there must be a leak in the iron. “There’s no leak!”, said Steve.
Finally, he called in another builder to investigate who found that the builder had ignored two very simple but important things. Firstly, the shallower a roof is, the more critical the overhang of the roof into the gutter. As Steve’s roof was a very shallow pitch - about 12 degrees - the roof sheet needed to overhang the gutter by about a 50mm to 60mm. Steve’s had only a 20mm overhang.
In addition, the builder’s blanket is supposed to be carried over the last batten and down into the gutter because it has to carry the condensation that forms in the roof space down into the gutter. Doing this properly though means that about 100mm from the end of the builder’s blanket the fibreglass must be removed so there’s no wick, just foil.
The new builder fixed the problem by installing a flashing 50mm down into the back of the gutter and 120mm up under the builder’s blanket. Michael, the builder, was amazed at how wet it was already.
“It was like someone had a hose running under there,” he says. “The builder’s blanket was wringing wet which meant that the last batten, the top of the facscia and the ends of the rafters were sopping. If that had continued they would have rotted - decomposition was already occurring, fungus already growing on things, and even now it may not dry out totally.”
Michael says that with the heat under the roof it’s a perfect environment for mould and rot. “It’s a dark, hot, wet environment,” he says. “Unfortunately this isn’t uncommon, because a lot of guys don’t care too much how they do it. Left untreated you’d be taking the roof right off to fix it - which would cost thousands.”
{ 0 comments… add one now }