Attaching polycarbonate to a cold frame

[Johnny Penstemon]

Hi all, I want to top my new cold frame with 10mm twin wall polycarbonate, which will be screwed to a wood frame to form the lid.

To attach poly to frame I bought the fancy cushioned button fixings (left of pic 1) but they are expensive monsters at 40mm wide and need wider lid timber than is ideal.

Question is, can I use the smaller button screws (right of pic 1), which are only ever listed for use with corrugated polycarb rather than twin wall? The screws are the same length in either case. I don’t want to compromise the twin wall in future, but with no wind lift/structural integrity issues as it’s a ground-hugging cold frame the smaller style fixings are tempting. Anyone used them with twin wall polycarb successfully?

Thanks Johnny

 

[scbk]

It won't need much to hold it, normal countersunk woodscrews and metal washers would do (both stainless if you want to be fancy). Or pan head screws. Or TEK screws.

Or even normal countersunk screws on their own, if you're careful.

 

[Johnny Penstemon]

Cheers scbk. I think my main concern is water getting in around the screw holes and discolouring the poly flutes inside. The fancy big ones are (over?)engineered to prevent that.

 

[Why Not Indeed]

Dab of silicone?

 

[catlad]

The smaller clear ones are perfect.