For maximum frame & fastener life use redwood, cedar or cypress. Avoid sap wood.
Seal high moisture areas of frame with satin marine spar varnish or Varathane. This protects top & bottom plate, and areas where polycarbonate contacts wood. This decreases wood rot, stops wood discoloration and creates a barrier between the chemicals in pressure treated and the polycarbonate. The smooth, nonporous surface is ideal for placement of foam tape. See last page of Franung Guide and Install Manua for info on use of foam tape.
#300 series - 18.8 stainless steel screws should be used with ACQ Treated Lumber. Other screws will corrode
Our standard screws are hardened carbon steel with a special Organic Polymer Coating. This screw is appropriate for all species of wood. The ACQ chemical will corrode the screw, so we do not recommend using ACQ if possible.
We do have an option for fastening polycarbonate to ACQ pressure treated, should you need to.
The option is separate, unpainted and unassembled, pan head - style 18.8 series stainless steel screws and separate washers. These screws are softer and one has to set carefully or the screw will snap. Cost is about twice the cost of of our standard steel screw assemblies, and are sold in the same 250 bag qualtity.
Simple solution is avoid ACQ.