Around 60% to 70% of solar installations are not installed correctly.
The most expensive mistakes begin at the foundation: mounting the substructure on the roof.
On detached houses, solar panels should generally be installed in portrait orientation. On barns, halls and commercial buildings, landscape orientation is often preferable.
Why does orientation matter?
It can save a considerable amount of material, labour and money.
A panel measuring approximately 1.8 metres by 1 metre requires only about 1 metre of rail length when installed in portrait orientation. In landscape orientation, the rail requirement can be around 1.8 times higher, requiring more rails, roof hooks, screws and related components.
On a typical detached house, the upper load-bearing roof timbers are rafters. They run from the ridge down to the eaves.
Barns, halls and commercial buildings often use purlins as the load-bearing structure. Purlins run horizontally, so the solar mounting rails are commonly installed vertically. The mounting rails therefore run at a 90-degree angle to the load-bearing roof structure.
The roof hook is fixed to the rafter or purlin beneath the battens.
For clay roof tiles, material is sometimes removed with a hammer to provide clearance for the roof-hook bracket. This can cause microcracks in the tile. Concrete tiles are generally cut with a suitable cutting tool.
Required clearance between roof hook and tile
Maintain a clearance of 2 mm to 4 mm.
If the roof-hook base plate must be packed or levelled, use only hardwood, stainless steel or rigid plastic. Multi-adjustable roof hooks are preferable because they can eliminate the need for packing.
Important screw requirements
- The screw must remain surrounded by at least 3 mm of timber on each side.
- For screw diameters greater than 8 mm, pre-drill with a 7 mm bit.
- The screw should be embedded at least 4 cm—and preferably 6 cm—into the rafter.
Conclusion: Installing solar panels as a DIY project is possible when the work is planned correctly. Modern mounting systems are robust and straightforward to handle. Roofers can also install solar roof hooks and panels efficiently. If you have questions, use the free technical guidance backed by 30 years of experience.
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