A.Rob Corbo, a general contractor in
Elizabeth, N.J., responds: After you've double-checked the
dimensions of your window to verify that it meets egress window
code, I'd recommend that you also double-check the conditions
around the proposed opening in the foundation.
If excavation will be required to accommodate the new window,
be aware that making grade changes could introduce
complications. You don't want water running toward the house,
so you may need to add money to the budget to address that
issue. You'll also need to temporarily support loads over the
opening with a 4-by-8-inch header that's long enough to hold up
the joists above the window opening plus two extra joists on
each side. Install the temporary header close to the wall, but
leave enough room — 2 or 3 feet should be enough —
While you can build the permanent header out of
concrete-filled lintel blocks supported by angle irons, an
easier option is to use a precast reinforced-concrete lintel.
These are available at most building yards, and will need to be
sized to your specific opening and cut to length on site.
Because these lintels may develop cracks over time, I like to
reinforce them with angle iron as added insurance against
callbacks (see illustration).
When cutting an opening in an existing
block wall, try to align it with existing mortar joints, and
size the new lintel so that it is supported by at least 6
inches of block on either side. Though structurally
unnecessary, a pair of angle irons provides extra support that
helps eliminate minor cracking in doubled-up precast lintels
The first course of block below the mudsill will house the
lintel, which should extend roughly 6 inches in either
direction past the window's rough opening. Using a level, mark
the lintel and window roughs on the foundation wall, aligned if
possible with existing mortar joints. The outline will resemble
a rather fat T. Using a masonry drill held as level as
possible, drill through the wall at all six corners to mark
your roughs on the exterior wall of the foundation. Use a
circular saw or a grinder equipped with a masonry or diamond
blade to score the wall on the interior and exterior markings.
This will create plenty of dust, so be sure to protect yourself
and the room.
Once the wall has been scored, start to chip away, starting in
the center of the opening and working toward the perimeter. We
use a rotary hammer but always have a 3-pound lump hammer and
cold chisel close at hand; we periodically remove the debris
underfoot to keep the work area clean.
Once you've opened up the wall, you'll have a number of
partial concrete blocks that will need to be filled or
replaced. Repair the opening as required, adding wire mesh to
the cavities to give your mortar something to hold on to.
Finally, install the lintel, shimming or jacking it flush to
the sill and packing the bearing shelves you've created
underneath with mortar.
Once the lintel is secure and the mortar has set, you can go
ahead and remove the temporary header and posts, apply stucco
as required, and install the window.