View Full Version : Masonry block advice please

John Elliott
15th February 2006, 08:50 AM
Can anyone advise me about blocking in a box a/c hole in a masonry wall?
I can get the blocks to fit the hole but is there a standard method of tying them in? And what sort of mortar should I use?

As these box a/cs are now on their way out, as part of our commitment to lower greenhouse gasses, this should become a popular pastime!

I would also like to block in an arched window, roughly semicircular in shape, about 1.5m wide by about .9 high. A bit trickier. Is this possible or should I get an expert in?

Thanks.....John Ellliott.

15th February 2006, 11:31 AM
Why not use glass blocks and let a bit more natural light in

19th February 2006, 08:25 AM
You dont need an expert you can do it yourself pretty easy.
Are they blocks or bricks? I presume being in townsville they are blocks.
You dont need to tie in as the mortar will be strong enough. Just use a ratio of 3:1.5:0.5 sand, cement, lime and you will be fine.
Use string lines for each course and practice getting the mud mix perfet consistency before you start.

19th February 2006, 11:39 AM
Is it renderred or face blockwork? Do you need to cut the blocks to make them fit? If it's face work and the opening does not exactly suit blocks, you may end up with odd cuts, which can make it look messy. Is the wall 200 series (8")? What is the exact dimensios of the opening? A bit of bondcrete on the surface of the blocks of the opening probably would'nt hurt either. Also, is there any power wires in the opening? Another idea might be to lay 100 series blocks flush with the outside, leaving a recessed opening 100 deep on the inside (or outside) as a feature to display somthing in.
For the arched window, the problem is cutting the blocks to the arch, and if its faced blockwork, it will probably look a bit wierd even if an 'expert' does it.

John Elliott
19th February 2006, 08:16 PM
Thanks. I appreciate the input so far.

The wall in question is masonry block (though there are plenty of brick homes in the neighbourhood - even in Townsville!) rendered on the outside and plastered on the inside.
The a/c hole is pretty easy being exactly 2 courses high (400mm) and 660 wide, so I just need to get 2 blocks cut. Do I need to put anything on the outside surface before rendering? Or on the inside surface before plastering?
Thanks for the mud mix recipe! ;)
Any hints on a recipe for render?:confused:

The semi-circular window is more difficult. It is 900 high and 1600 wide and has a masonry sill built in.
Will there be a bond beam above the arch?

For a small job there sure are a lot of questions....

Thanks........John Elliott.

20th February 2006, 02:39 PM
wouldnt expect a bond beam above an arch. bond beams are usually in the top course of walls built to cyclone code.
the semi-circle can be traced and transferred to the block and trimmed with an angle grinder. accuracy can be rough because you are rendering anyway.
if the sill is protruding i would remove it 1st.
no need to put anything on outside or inside before rendering. the render will adhere via what is called a "splatter coat" or "scratch coat". however i dont know too much about rendering. standard thickness is 19mm thick render to the exterior and 15mm to the inside. i