I'm going to install a through-wall air conditioner using a purpose-built sleeve. The instructions from the manufacturer say to install it such that it angles slightly downwards to the outside (about six degrees) so any condensation or rainwater will run off and drain outside the house.
All the instructions and how-to guides I've read show the framing (header, supporting studs, etc.) installed level and at right angles. The only thing I've seen that gives any indication of how to properly arrange the frame to support the downward installation is to install the header 1/4" above the actual size needed for the sleeve opening so that it falls back and down to the outside a bit.
Is this the correct way to do this? Should the sleeve be shimmed at the bottom or should the horizontal studs be installed at a slight angle so the sleeve sits flush with the header and horizontal support stud?
I haven't done this before so any insight on how to get the installation angle correct and still maintain a proper safe and secure installation is appreciated.
Best Answer
It's much easier to check that something is level than to check that something is 6 degrees or 1/4 inch higher.
Build it level. Then add a 1/4 inch strip of wood (a length of lath or trim) across the inside edge of the horizontal framing member.
You are correct that the sleeve will be sitting on two edges, the added trim strip and the outside edge of the exterior horizontal member. But the air conditiner is quite rigid and the sleeve sufficiently so to resist flex. The weight is not so great that the boards will be compressed or the machine flexed.