I'm helping a friend install hurricane panels over the windows in their house. These panels are 5/8"-thick extruded clear(ish) plastic sheets, dimensionally similar to 5/8" plywood. These panels are removable, obviously not mounted and stored (usually in the garage) when not in a hurricane situation.
There are two typical anchor methods for these types of panels (or other similar panels):
- Permanently install threaded studs into the wall. These threaded studs are often (usually?) Tapcon SG into the wood or block substrate, with a 1/4"–20 machine thread sticking out, so that the panels can be attached with washered-wingnuts. When the panels aren't installed during a storm, the exposed machine threads are usually covered with a plastic or nylon cover.
- Permanently install female machine thread anchors, to receive "street bolts" or other large head 1/4"–20 machine screws to hold the panels onto the wall. When the panels aren't installed during a storm, short street bolts, or plastic bolt-shaped inserts, are placed into the threads to protect them from dirt and moisture.
My friend wants to use method 2 (permanent female threaded inserts) for aesthetic reasons. My friend's house is block construction, but in my experience hanging plywood over the windows in previous years, I don't believe the block voids surrounding the windows are filled with poured concrete. At least, I can't assume they are.
The anchors will be about 3 inches beyond the stucco corner. I believe that for the most part, I will be drilling to the block voids, not the web or the mortar between blocks. Given that, what is the best type of anchor to install?
From what I understand, ''single-expansion'' anchors only expand from the bottom, which provide no hold in block voids (because the expansion occurs beyond the thickness of the block, and also because the block will tend to spall when drilled into the void, reducing the effective thickness of the wall of the block). ''Double-expansion'' anchors, from what I've read, can be okay in the void of the block, but I wonder if they're good for non-permanently installed threads/screws?
Is an epoxy female thread anchor the best option? Again, only the female anchor will be permanently installed, threading in a bolt only when needed during storms. I've also seen lead+brass sleeves that expand during installation, leaving a reusable female thread.