You can’t walk directly on the polycarbonate. This will dent and damage it. If you do need to get on top we recommend using a walk board at least 2-3m long across the sheets on top of the purlins. Take care not to scratch the sheets with it.
Here is a recent question:
Is there thicker polycarb roofing which is safe to walk on? With all the health and safety madness we have nowadays I’m a little concerned that someone will walk on the skylight and fall through, and blame me.
I guess from your reply, its not a great idea to have two sheets to increase the thickness. Will this cause over heating, and damage to the polycarb?
We don’t recommend walking on the polycarbonate. There aren’t many options as far as that goes. It’s called being ‘trafficable’ and is a requirement for schools etc. just in case kids get up there and walk on them.
There are commercial options of the fibreglass roofing, which have a mesh built into them. These are very expensive, and generally specified for schools.
The other option is to put roofing mesh (similar to chicken wire) underneath it first. This is also a generally accepted practice. That way, even if the sheets deteriorate after many years, the mesh is still there to stop anyone falling through.
We don’t recommend putting two sheets together to increase the thickness. Mainly because of the heat that can get trapped between them, but it also gets very difficult to clean in-between them if any water / sediment / mould gets in there.
The roofing mesh might be the best option for you?