When it comes to leaks, low pitch roofs are the most vulnerable.
Roofs between 1 and 4.9 degrees are considered to be low pitch. Only a few types of roofing profiles are made to be installed at such low degrees, including mono clad (Trim Deck) and concealed fix (Klip Lock, Speed Deck, and Top Deck). There are more options than these, but if budget is a priority, the profiles listed above are the best value.
Why do we build almost flat roofs?
Why we build low pitch roofs really depends on what the building is being used for. Here are a couple of common reasons:
- To save money. Commercial and industrial buildings are generally very large and constructed using a steel structure. Built to as tight a budget as possible, the less material used, the better.
- To create architectural interest. Residential houses and architecturally-designed commercial buildings often use a low pitch roof to add a modern design element. A low pitch roof can also be hidden behind walls known as parapets and usually involve a box gutter.
Will low pitch roofs leak?
If a flat roof is not properly installed, it will leak — guaranteed. Only work with the best of the best to ensure your low pitch roof stands the test of time.
Here are five critical control measures to use to stop a flat roof leaking.
5 control measures to stop a flat roof leaking
- Install roofing material to the manufacturer’s recommendations. This may seem straight forward, but it’s something we see time and time again on DIY projects and extensions. Most manufacturers will recommend turning up the top of the sheets and turning down the bottom, which must be completed using a turn up and turn down tool.
- Extend roof sheets further into the gutter. The more overhang you can achieve into a gutter, the less chance you have in capillary action of water creeping back up the roof sheet and entering the roof. The minimum standard is 50mm. On a flat roof, we suggest starting at 100mm of overhang. If you can, aim for 150mm. Just make sure you leave enough room for gutter maintenance.
- Install a gutter flashing between the gutter and the roof sheeting. This flashing rests on the front edge of the lowest batten with a squash fold to direct any possible water flow sideways instead of back into the roof. This flashing is also a must when installing profile filler at the gutter edge.
- Profile fillers at the tops and bottoms of sheets. At the gutter edge of the roof, install a pre-formed foam filler between the roof sheet and the gutter flashing. This will act as a physical water barrier. Install a profile filler at the highest points under a ridge cap or apron flashing to stop water ingress into the building.
- Under seal all flashings with a substantial amount of quality silicone. Rivet the joints of the flashings at 40mm increments and fill the rivets with silicone.
6 things to be aware of that could cause problems
- 1* Roof pitches are never a good idea. If it’s not built properly, there’s potential for negative pitch. If your roof features an under 2 degree pitch, a maintenance schedule must be recorded to attain your warranty from Bluescope.
- Cheap silicone will break down quickly and create easy access for water.
- Roof and gutter maintenance must be carried out to ensure no debris is blocking water flow.
- Any additional items installed onto the roof can increase the chance of leaks if not installed correctly.
- Commercial roofs will always leak where mechanical equipment is installed if penetrations through the roof have not been installed and sealed by a qualified roofer or plumber. We strongly advise a thorough water testing process is undertaken after penetrations have been sealed before mechanicals are connected.
- Solar panel installation must be done using proper mounting brackets that clip over the roof sheeting but don’t penetrate the roof.
Find out more about low pitch roofs today
Low pitch roofs that are installed properly by skilled tradespeople and have a high level of control measures in place will create a fantastic result that no other material can duplicate. Low pitch roofs certainly represent metal roofing at its finest.
UPDATE: As per QBCC Guidelines –
Apron flashing over skillion patio roof extension to an existing roof.
When water can enter through a lap, it must be compressively sealed with an appropriate sealant.
The solutions provided are typical only and have been gathered from current and relevant building codes and Australian Standards. The methodologies described aim to achieve water-tightness by mechanical means rather than an over-reliance upon the use of sealants.
Building projects may often require the adaptation or development of ideas and solutions using the principles of sound waterproofing and flashing techniques as described in this fact sheet.