Creating a watertight metal roof, whether a DIY standing seam roofing project, or any other kind of metal roof, can be a far more complex process that initially contemplated – particularly if using pre colored sheeting, where painting over waterproofing is not a viable option. Here are a few of the basics you need to consider to make sure you have a leak proof metal roof.
When undertaking a DIY standing seam roof, or another metal roofing project, investigating these waterproofing tips will certainly offer a roof with a much longer lifespan!
Metal Sheet Fixings
Choosing the right fixing for your new metal roofing is critical. Factors to be considered are the base structure – is it timber or wood? The type of sheeting also plays a role, with regards to the length of fixing, as does the sheet finish – galvanized sheeting requires galvanized screws or nails, while zincalume requires a zincalume screw or nail.
Most important, choose a fixing with a built in cap. These are both weatherproof, being plastic, and help coordinate with color sheeting – the cap being available in a range of colors. DIY standing seam roofing projects in particular can be made much easier by using the right fixings!
There are a variety of sealants around, the two major groups being silicone or mastic. Silicone has the benefit of being available in a clear variant, therefore being invisible once applied. Mastic however, often offers a much longer lifespan, since it does not dry out or shrink.
Polyclosures are die cut polyester foam rubber strips, cut to follow the contour of the sheet profile. Fitted under flashings, and secured with silicone or mastic, they prevent wind driven moisture from entering the roof space under the flashings. Most companies offering wholesale metal roof materials will also offer a specifically designed polyclosure for the profile you choose.
Depending of the layout of your roof, you may require any one, or a combination of sidewall, headwall, ridge, hip or apron flashings, or perhaps another specialized flashing altogether. Flashings are generally affixed after the metal roof sheeting is completely laid and trimmed, and affixed using stainless steel or aluminum rivets. These rivets should then be sealed with silicone or mastic. Careful planning when deciding how to install a metal roof will mean that you have all of these, and other accessories on hand, and don’t experience any delays!
Where chimneys are fitted lower on a pitched roof, a special flashing is generally manufactured. Called a soaker sheet, they are designed to channel all water that would accumulate behind a chimney around the chimney and off the roof, thereby preventing water from damming up behind chimneys and damaging the metal sheeting.
Roof sheeting is always laid lengthways, so that the pan, or channels, can divert water off the roof. The sheets always overlap, known as a side lap, usually by one rib. However, on very low pitches, particularly when using a poor water channeller such as corrugated sheeting, double laps (two rib overlaps) may be a good idea.
It is also never a good idea to end lap a sheet. This means to overlap the sheet lengthways with another sheet. While it may save money in the short term, the overlap will almost always be the site of rust, since water will seep between the two sheets and accumulate there. Asking a roofing professional for metal roof installation instructions can certainly help avoid this kind of mistake!
When in doubt with regards to waterproofing accessories for your metal roof, whether a DIY standing seam roofing project, or otherwise, it would be advisable to seek out a roofing professional or sheeting manufacturer for advice. Many offer free advisory, or even estimating services, to help you make the right choices for you roof.