What is better? Rafters or deck screws?

Many installers in BC use deck screws to install solar footings to the plywood on your roof. That can be problematic for a number of reasons. A solar footing or L-foot is essentially the attachment point for the solar to be fastened to your roof. These footings are fixed to the roof using various methods, which then house the railing system to which the solar panels are clamped. It is becoming more popular to use decking screws to fix these footings to the roof as it is quicker and installers can essentially place them anywhere. At Pure Solar, we refuse to use deck screws and instead opt to drive lag bolts into the rafters of your roof using metal flashings, and here’s why…

Rafters are structurally sound, and mounting to them means fewer mounts, which means fewer holes. Applying deck screws requires at least 2-4 roof penetrations per footing, meaning 2-4x as many holes in your roof. Think of trusses like bones in the human body and the plywood or roof decking, like skin. There is a different structural value to attaching hardware to each of these properties. Roof decking or ply has a flex property which means that uplift and down force from events such as wind and snow, plays a greater impact on your system. As it moves over time, screws loosen and hardware fails.

Trusses have a far superior downforce strength and when considering the uplift forces would you rather rely on rooftop ply or your structural rafters to keep your system fastened to your roof? In windy conditions, your system acts like a giant sail on your roof. Not to mention, when using decking screws, you have no idea what the condition of the rooftop ply underlay is, or how thick it is. Would you rather have your system built into the integrity of your home through rafter mounts or risk that a small portion of thread on decking screws will hold firm through the ply underlay on your roof?

The climate in Vancouver is similar to that of a rainforest during the winter months. Eventually, cheap hardware will fail, and with it, so will the waterproof seal on your roof. With 2-4x as many penetrations, that’s a lot of opportunity for moisture to find an entry into your roof cavity.

It’s not cheaper to install with one vs the other, but it is quicker to use roofing screws as you can install them anywhere. It means installers can literally lay footings wherever they want. And so, many installers will opt for the quicker and easier method… We don’t mind taking the extra time and care to find your rafters, as we then know that we have integrated your system into the structure of your roof. 

We don’t compromise on doing things properly and we don’t compromise the integrity of your roof seal. At Pure Solar, we’ve never had a leak, never had a call-back, never had an issue, and never had an unsatisfied customer. We will NEVER stray from doing things the right way and installing systems that will outlast their warranties.

Leave a Comment

Your email address will not be published. Required fields are marked *