I have cut a window opening for installing a new window in an exterior
concrete block wall.

The window brochure says this is a "H33" window, the size is 26 1/2" W x 38
3/8" H and it called for a rough opening to be 1/2" larger in either
dimensions. This means the rough opening need to be 27" W x 38 7/8" H which
is what I cut the concrete opening to be.

However, when I looked at other window brochures, I see more terms - CALL
size, BUCK size, FLANGE size and they are all a bit different...

Also, I talked to one window contractor and he told me he has to fill in the
concrete block voids with solid concrete then screw the window onto the
concrete with Tapcon. Another window contractor told me he would install an
interior frame of PT lumber around the concrete opening, attach the wood
frame to concrete and then attach the window to the wood frame. The first
contractor says this does not work as the window would be blown away during
a hurricane.

Now I am wondering, what does the "rough in" mean, it means the concrete
opening or the opening after installing the wood frame? Do I really need a
wood frame?

Confused.

Thanks in advance,

MC