# Forum Home Renovation Brickwork  Cutting a hole in Besser Blocks

## yhenig

Hi. I need to cut a hole for a window. Wall is made of Besser and I wonder if any one got a hint for the best way to mark it so when I cut from both sides, the alignment will be good. 
Thanks in advance.

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## AIRMAN

Mark it on the out side and drill and hole in each corner the whole way through, on the inside simply mark it out by connecting the 4 holes. 
Remember depending on the wall and the window you may need to put in a lintel

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## wizard

Excellent advice from AIRMAN  :2thumbsup: 
Dont forget to check for wiring and or plumbing in the wall, and measure and mark evrything at least twice before you start. It is often handy to have the window on site before you start.... less chance of a mistake.
Cheers

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## Blocklayer

What size blocks - what saw and what size window?
Does it need a sill and what head height will the window be?
Is the wall core filled, is there a bond beam on top and if so, at what height and how many courses (drilling small holes in block cores should discover this)
Depending on the above, if you position the window so the cuts go through a block web, you'll need to cut through the entire (concrete) block, as opposed to cutting through empty cores, where you only cut through the thin wall of the blocks. 
Depending on all this, don't forget if you go through the cores, and they're say 200mm blocks, you'll end up with recesses on the edges, back inside the cores, so you may need to cut wider and trim the hole out with timber or something. 
And like Wizard said, check for wiring and or plumbing 
Also as Airman said, what about the lintel? Is anything bearing on the wall above where the window will go? 
Lots of things to consider here.

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## yhenig

thanks gusy. it's only a small window: 600mm width and i've checked for solid core, wiring and plumbing: non. it's a 200mm block and i was planning to use a big angle grinder with a concrete wheel. The idea of drilling holes sound good to me. Thanks again.

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## Blocklayer

> it's a 200mm block and i was planning to use a big angle grinder with a concrete wheel.

  Is it very far to the nearest Hospital? 
.

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## Bloss

> Is it very far to the nearest Hospital?.

  So he'll be able to hobble there when he takes his legs off at the knees?    :Biggrin:  Or he could just end up a pretty 'armless sort of bloke?  :Biggrin:

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## AIRMAN

Reading that brings back memories of when I was 17. I was a @@@@ kicker for a brickie, on one job the builder had said right at the end that one wall needed an expansion gap in it, it was a 2 story house on a slope, they sent me up a fully extended ladder with a full size concrete saw and expected me to be able to make a perfect cut the full height and perfect depth, I only made it as far as the top of the ladder before I gave up. No one else wanted to try so it went on the too hard list and was never done.  It was good to see OH&S was alive and well.

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## Blocklayer

Did you cut the hole yet? 
How did it work out? 
.

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## yhenig

Yes, no problems. Initially I didn't 'like' the responses. However, I took the 'advices' and was extra careful. I've used angle grinders before so i knew what i was doing but still, the extra care was worth it. Thanks for asking anyway.

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## autogenous

How are you going to finish the reveals? 
The blocks are cored? Are you going to render, architrave, sheet the reveals? 
This may effect the size of the opening. If any of the above are bigger than the profile of the window jamb they will protrude even potentially over the glass. 
You may have to make the opening slightly bigger? or possibly rebate the block so the reveal cover doesnt extend beyond the window jamb? 
If you have to fit a flat bar you may have to add an extra 10-12mm to the cut out height for the lintel? 
Do you have a picture? 
Does that make sense?

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