I would like to build an egress window in my basement as there is
currently only one way out and that is right next to the furnace. It
doesn't seem like it would be too difficult as the material is readily
available. The one thing I can't figure out is how to cut a straight
line through the cement block for the opening. Is there a saws-all that
cuts through cement? Any ideas?
I've used a circular saw with a masonry blade on a basement floor. Would
probably be my choice for block wall as well.
Do a little research. Maybe call a rental center...
- jbd in Denver
I've cut concrete and terracotta that way also but it
kills the saw. Abrasive dust quickly erodes the bearings
and commutator. If you have an old saw that deserves to
be tossed anyhow, go for it, but don't risk a nice saw.
Yes, there are abrasive blades and diamond tipped blades. If you have a lot
to cut, it may make sense to have a pro do it. Some will give you a price
on the phone if you give them the thickness and size to cut. Not cheap, but
A perfect cut is nearly impossible in concrete block walls because the
block is hollow leaving holes you can't fasten bucks or windows to.
Just break out the entire blocks and lay in new corner(smooth ended) and
cap (smooth top) block cut to size with a diamond blade or abrasive
blade in a throw away skill saw. Don't forget to look at the head of
the window to determine if a lintel or header is needed to carry the
load from above. It doesn't take much weight on top of the window to
I put down some Bluestone and bought a diamond blade to cut them.
Later I needed to cut some 8" block and the thing goes through them
like butter - well almost.
Mine is a Continuous Rim blade and I paid about $60 for it.
I agree with others, the diamond continous rimmed blades work well.
I've got one for the 4.5" angle grinder, and worm drive saw...and both
work extremely well. And yes it's hard on the grinder and/or saw.
I've probably cut as much concrete as wood with the saw...and now it's
a dedicated concrete cutter. I don't know how the blades work with a
traditional saw. Another tool that works VERY well, and doesn't cost
much money is the little pneumatic air hammer, the flat bit smooths up
the cuts and the pointed one removes material very quickly. It acts
like a mini-jackhammer.
When making your rough opening...depending on the size of the window
and it's desired placement, try to stay away from the middle webs, and
ends of the block, it's much thicker there. Don't forget, cement block
chips easily with a 3 pound hammer, so you don't have to cut it all,
concrete chisles work well. By the way, give yourself at least an
additional inch on the block side of your rough opening mateial...don't
make it too tight otherwise you'll be fighting the framing material
when squaring up. Great stuff seals any large non-structural gaps
Don't worry if there's reinforcing metal webbing, the saw blades zip
right through them.
The first window I installed, I used the chainsaw type concrete
saw...man that baby stinks up the house and just about kills the
operator outside in the hole, not recommened, overkill.
By the way, one last thought, I would stay away from the item called
scape-well, it's a plastic surround, that bolts to the exteior basement
wall. not a very well built product. I use PT material and the seem
to hold up well, with backfilled with large stone.
A couple of other thoughts, make sure you wear adequate air masks,
safety glasses and use lots of fans to make sure you control the dust.
I have on occasion sledged out a medium sizied hole in the block where
the window will go, and wired a regular window fan into the hole which
helps pull the dust out.
Most rental centers have concrete saws for that job- and that is
really the way to go. But that's a kind of a nasty job you've got in
mind there, lots of noise and dust- and then you have to worry about
making sure it's sealed properly once you've got it done. If you
haven't thought of it, there are pull-down stairs that will go between
two floor joists with some minimal framing and cutting for an
There might be a reason why you prefer the window option, but the
stairs are a reasonable alternative if you concern is mainly about
having a second exit- I know for myself, I'd rather mess with the
foundation of my house as little as humanly possible.
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