This is our first attempt at a modest addition to our house. We will be screening in our front porch, however the existing beam on the corner has a sheet metal cover on it. I am able to press the metal in an inch or two before it actually hits wood. My question is, won't my measurements be off if I measure from the edge of the metal? I feel like there needs to be some compensation for the metal beam covers, or should it maybe be removed all together before installing? I've done a fair amount of research on framing, however I never seem to find anything specific to my situation. Thanks in advance!