Cutting rough opening in a cinder block wall
I would like to know how to
install a steel door (already purchased and pre-hung) into my basement
cinder block wall. There isn't a hole there so we'll need to cut
a hole through the concrete block wall. I need to know the best
way to do that. We won't have to move any outside dirt; the opening
is already at ground level. Please get back to me about this, thank
Installing the pre-hung door will be breeze compared to cutting the opening
for the door. If you had a concrete wall I would suggest that you
hire a company that specializes in concrete cutting. Cutting cinder
blocks will be a project but it can be handled in a weekend. The
question is, where should you begin? First, get a building permit,
and second, determine your ceiling height. This is important because
you need to know if you have the proper height for a pre-hung. Also
check to see if the cinder blocks are below ground level and how
many blocks will remain above the door (header area). Most likely
you will need to take the blocks all the way up to the underside
of the sill plate and only down far enough to be level with the
finish floor in the basement.
Start by putting up a temporary wall under and across the joists
where the exterior wall will be opened up. Leave enough space between
this wall and the cinder block wall so you have enough room to work.
This project will require you to cut the wall on both the exterior
and interior sides of the cinder block wall, so it is important
to know the rough opening of the wall. To determine this, measure
the overall width of the pre-hung doorframe and add 1/2"
and another 6". (Your header will be this width measurement
minus 3". The 3" is for the two studs that will be nailed
to the ends of the header. The other 3" is for trimmers to
be nailed to the studs under the header to support it. The 1/2"
is the space needed to adjust the pre-hung door using shims.) Take
this measurement and mark it on the wall both on the exterior and
interior sides. Use a straightedge to draw the cut lines and make
sure that the cut lines are level and plumb and the measurements
between them are the same. Take care so the cut lines land on the
outside of the center support of the cinder blocks.
Hang plastic from ceiling to floor around the work area
to help contain the dust. Now, make sure you are wearing safety
glasses, hearing protection, and a mask when you begin this next
phase of the project. Take a 4- or 5-pound hammer and punch
about a 10" (or larger) hole in the wall to the outside in
the center of the rough opening. This hole is necessary for fresh
air and helps move the dust to the outside while you cut the wall.
Then use a circular saw and masonry saw blade to score/cut the cut
lines. Once the cut lines have been scored/cut on both sides, you
can start breaking out the blocks. Take your time and be careful
when breaking out the blocks near the cut line. You may need to
use a masonry chisel to break any cinder blocks that are attached
in the center of the block.
Once this area is clean, it's time to access the opening for framing.
It is possible that your rough opening landed in the center of some
cinder blocks. If this is the case, then concrete can be poured
from the top into these areas, but you will need to build a form
in front of these areas to hold the cement while it cures. The form
can be supported by 2x material wedged into place horizontally within
the rough opening—i.e., up against the form and the cut cinder
block on the opposite side. You may need to form up both sides.
Before you start this, do a quick double-check on your rough opening
measurements. Before pouring any concrete is a good time to enlarge
the opening if necessary.
The frame including the header can be pre-built and placed within
the rough opening with the trimmers added last; however, before
building the frame, temporarily attach your studs (2x) to the cinder
blocks using lead anchors and at least 3 lag screws per stud. This
will require a masonry drill bit and wood bit. Once you've done
a trial fit, build your frame and reinstall the lag screws. The
heads of the lags will stick out so you will need to drill a hole
large enough on the backside of the trimmers in order for the trimmer
to lie flat up against the studs. Consider using screws instead
of nails and pre-drill when attaching the trimmers.
When completed, you will have a wide rough opening that will require
jamb extensions unless your pre-hung door is custom-built to fit
that width. As you install the pre-hung door, keep in mind that
if the door is going to swing to the exterior side, the door's frame
needs to be flush to the exterior wall. If the swing is to the interior
side, then the door's frame needs to be flush with the interior
wall. If your door is custom-built, it is already fabricated for
the proper installation. If you are going to build your own jamb
extensions, putting the door in either of these positions will prevent
you from butting the jamb extension up against the hinges. It will
force you to put the jamb extensions on the opposite side of the
frame, where it is required. Good luck with the project—you'll
have your hands full on this one!
2001 & 2006 LAF/C.R.S., Inc. All rights reserved.
Question answered by Leon A. Frechette.
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