By Ethan Bickford
A few years ago fastener manufacturers started making screws with reverse threads near the head of the screw to prevent “mushrooming” in composite and plastic building materials like decking and PVC trim.
I’ve used the The Cortex Concealed Fastening System many times before and have found that is is one of the fastest and easiest way to conceal the fastener heads when installing PVC trim boards. It totally eliminates wood filler and sanding. The cortex system comes with screws, plugs, and setting tools. Available in a 50, 250 and 750 lin ft box.
These screws do a great job at prevent mushrooming but they also have another unique characteristic.
Expensive shims but worth it!
When fastening PVC trim around flanged windows the window flanges prevent the trim from sitting flush against the house. So you get some unwanted reveals and ugly joints. But this can be corrected by just slightly backing out some of the screws used to fasten the trim. When you back the screw out it pulls the fastened material away from the substrate. This characteristic can be frustrating when you’re trying to remove a screw but it can also be used to your advantage.
Read more about these fasteners and plugs here: Installing Hidden fasteners in PVC trim