Other considerations for the rainscreen veneer attachment systems available on the market are accommodating the installation of the continuous insulation and the fastening requirements for the insulation. Cutting and trimming the insulation to fit within or around the attachment system requires additional labor. Installing fasteners through the insulation results in holes in the air and water (and vapor barrier) membranes installed on the exterior sheathing.
While manufacturers of the membranes have claimed them to be self-sealing or self-healing, their claims are based on testing done under ASTM D1970. This standard contains a nail seal ability test whereby the membrane is applied to a piece of plywood, a nail is driven through the membrane and plywood, pulled halfway back out and then the water tightness of the penetration or the nail through the membrane is tested by creating a horizontal reservoir of water around the penetration for a period of time.
This in no way simulates the penetration through the membrane of a screw type fastener which then penetrates the gypsum sheathing, stalls in inward progress while self-tapping a hole through the LGMF member and kicks out the gypsum core of the gypsum sheathing due to the action of the threads of the screw type fastener. The industry is aware of this issue and ASTM is currently working on a standard test method for determining fastener seal ability through these types of membranes.
What are the properties needed and wanted for a rainscreen veneer attachment system that can be used for all construction types?
- Does not burn
- Does not rely on plastic insulation to bear any imposed loads
- Installs easily with few parts to assemble
- Provides required adjust-ability without having to shim
- Reasonable cost
- Does not require cutting and fitting of insulation
- Provides for the mechanical fastening of the continuous insulation.
Results in minimal thermal bridging through the continuous insulation.
We searched for such a system but did not find it. So…….we invented it.