MiamiCuse wrote:
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?

It is common in Florida to install PT bucks on masonry to receive
windows when the ouside walls are to be stuccoed and trim around the
aluminum/vinyl windows is to be drywall. Windows properly installed
on them absolutely won't be blown away.

(The reference to flange size is for windows to be installed in wood
construction...the flange overlaps the wood structure and is nailed to
it.)

The window should be on a pre-cast sash which slopes downward from the
window and extends beyond the block wall. It has a raised water
stop/lip on the top upon which the window sits thus retaining the
window. There is also usually a recessed drip line on the underside
outboard of the block wall line. There is a lintel above the window
opening that spans it and extends onto the blocks at either side. My
lintels are precast concrete. Some builders use steel.

The bucks are a diagonal half of a piece roughly 3/4 x 3/4. One right
angle edge is against the concrete block, the other faces out. The
diagonal edge faces inside sloping from window frame to block. There
is/should be another piece of PT which extends 1/4" beyond the block
on the inside edge of the block along the vertical edges of the
opening.

To install, the window is lifted over the sash lip then screwed to the
bucks at sides and top.

The rocker shoves a piece of 1/2" drywall in against the sloping
buck...the slope pushes it toward the window frame...the rock is
nailed to the other piece of PT...the rock lays off the block because
the space is 3/4" and the rock is 1/2".

The inside surface of the concrete sash can be covered with whatever.
Builders often use polyester "marble" because buyers think it is real
marble and therefore luxurious. One can trim the other edges of the
window with materials other than drywall as well. All mine (except
one room) are Saltillo tile. The other room has butternut.

As far as rough openings goes, keep in mind the fact that all block
homes are limited in dimensions to a minimum 8" unit - a half block.
Openings in new block walls are going to be divisible by 8 and
manufacturers of stuff to go in the hole know that. Best suggestion I
can make is to call the manufacturer/distributor/retailer of the
window and ask. Best time to do that is before you chop holes in your
wall.

What I described above is normal for new construction. In new
construction, every opening is bounded by a vertical stack of blocks
with steel tied into the foundation; the top course of horizontal
blocks are "U" shaped; that "U" shaped lintel has steel put in the "U"
and tied into the steel from the posts; both the "U" and the posts are
then filled with concrete. The result is a very strong post and
lintel structure that is tied into the foundation; all the other
blocks are just "filler".

However, yours isn't new and you've cut through blocks exposing hollow
cells. Apparently, there is no lintel either. If that is the case
then you have compromised the structural integrity of your house and
I'd suggest you get someone out there that knows WTF they are doing.

--

dadiOH
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