I'm working with a veranda roof made out of corrugated polycarbonate similar to this stuff... corrugated plastic sheet. Is there anyway of working with this material from underneath?

The roof I'm working with is enclosed on three sides by high brick walls, the only way remove the panels seems to be to climb onto the roof, crawl several meters along the top and unscrew from above.

The first question is how did anyone fit it in the first place? All the instructions (plus a few youtube videos) show the panels been screwed down by a builder working from the sides, none of them show anyone being foolish enough to climb on top - the plastic is just too thin to support anyone.

Even if I were to use crawling boards to spread the load over the panels, I'm not sure the wooden frame underneath would take my weight (80kgs)

Second question, Assuming I manage to remove the old panels (somehow) are there any fittings manufactured that would allow me to attach new panels from underneath? Maybe a threaded nut fastener that could be attached to the top (outside), and then a threaded bolt inserted from the underside? Really don't fancy climbing on top, but the limited access from the sides doesn't seem to leave any options.


2 Answers 2


The section of polycarbonate roof was done from the side, one sheet at a time, while standing on a ladder probably.

Except the last sheet...

Follow the instructions for the sheets. E. G http://polycarbonate.com.au/suntuf-installation-guide-tips/

Most commonly, make sure correct side (UV resistant) up; and drill holes first which are larger than the roofing screws

The polycarbonate shrinks/expands with temperature changes, try not to install with edges hard up against anything.

If area is perfectly regular, you can test place a sheet up, mark lines, and drill all holes when safely on the ground.

With the last sheet, half the screws will have to be done the hard way.

Perhaps sit the screws in the last half sheet and gently lower;

But how to screw the last ones in from above? Fix long pole to electric screwdriver? Feel free to suggest.

An unusual problem I have seen once (Australia) is regularly spaced burn marks on the wood underneath.


Your support frame had better be strong enough!

First, the support frame must support snow load.

Second, the roof must be able to endure wind load or it would have been torn off in that storm, what was it, 15 years ago?

So if you feel the support frame is not well sufficient for both of those, then it too needs to be replaced. You've been lucky, and that is not a plan. So my first stop would be to look at the structural engineering of that stuff. You better be able to go on top of that stuff, or the wind will take it, or the snow will collapse it.

My go-to for weight spreading on that kind of roof is 4x8 (1200x2400mm) sheets of plywood 3/4" -1" (19-25mm) thick. Whatever standard plywood size you have over there.

It's too wide for (my) comfort

What you're working against is the fact that the stuff is designed for 3 foot wide pitch (900mm + 2"/50mm overlap). The stuff I use is 2 feet wide (600mm) + overlap (so 650mm) and my arms are that long. Which means, I only have to work on the outside of the building for the last sheet (first to remove). All others, I can use a ladder from inside, pop up, and reach over to run down fasteners.

You need lots of fasteners if you don't want it shearing off under wind load, and making a huge mess (not least: chunks of sheet being propelled by the wind and impaling other building structures or your car).

So I would shop around for (I would guess 650mm?) width of the stuff.

But you still need a strong enough frame structure!

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