When I think of a gutter apron, two options come to mind, both being a product made by Alcoa and used as part of a gutter installation system.
One is a combination drip edge, gutter apron called a
fascia apron. The bottom edge of this apron
is where the new gutter locks into, before the hangers are installed. On the type of apron, the hangers that are most effective are roof hangers, that being hangers that lay on the roof, nailed or screwed thru the plywood and into the rafters, before installing
any other product, including Ice & Water Shield.
In this case, the gutters get installed after the roof is stripped, and before the roof system is installed.
Unfortunately, it is impossible to pitch this gutter
as it sits tight to the fascia/ sheathing and can’t be adjusted. This method of installing the hanger under the roof is the only way to get the alcoa gutter to be installed according to manufacturers
instructions and qualify as properly installed and warranteable. The gutter is 100% floating. Any hangers that attach thru the back of the gutter,
restrict expansion of the gutter and cvause the system to fail inspection.
The gutter apron, which also attaches to the fascia,
but is installed to pitch whichever way you want, should also be installed before roofing, assuming that after the apron, gutters, and hangers are installed, a drip edge and membrane will be installed before starting to shingle.
I am sure that someone can point you in the direction of a website that shows a detail that
includes a 3x3 metal edging installed in the drip edge area, prior to shingling, that prevents ice and water back up when the gutter over flows.
Some times…“looks good”…and "done correctly"
are two different finished products. I prefer to add this 3x3 edging before installing gutters, and before shingling, as an added counter flashing.
It is simple to install when done prior to gutters, etc, and a real pain, when made with the idea to notch it around gutter hangers.
The gutters need to float, any quality roofer that
suggests Spike & Ferrules or thru gutter hanger systems is not advising you as to the best method.
I know this will bring up a lot of discussion, but
I ask…“how would you do it on your own house…
not what do most builders want to pay for.?”