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Bonding Metric Blocks with Imperial

Postby chuckp » Mon Jul 01, 2013 7:06 pm


I'm enlarging an existing shed that was built with (l)18" x (h)9" x (w)6" blocks and a 1" mortar bed.

Metric blocks have a nominal height of 225mm while my existing courses are roughly 255mm high (230mm for the blocks and 25mm for the bed). So I'm going to need a bed 40mm deep to line up the new blocks with the old.

1. Apart from the amount of mortar I'll need, is it ok to lay such a deep bed? It is just a garden shed.

2. Is is possible to buy new blocks which are closer to the imperial measurements?

3. Any other ideas?

Thanks for any help,
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Simply Build It

Postby welsh brickie » Tue Jul 02, 2013 5:26 am

you can use normal blocks, but for a bed of mortar that thick use either tiles or paving slabs bedded down first, the paving slabs have a thickness of 30mm
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Postby SMED » Tue Aug 27, 2013 9:52 pm

Hi Chuck
is the block work rendered? if it is, you don't need to "keep up" with course height.
the only reason metric face work needs to "keep up" with imperial is if you are trying to tooth into existing which seeing as this is block work I doubt you are??
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Postby chuckp » Thu Aug 29, 2013 9:52 am

Thanks for the replies. I was trying to tooth into the existing imperial courses.

In the end, and given it's a small shed, I knocked down blocks from the top of the existing walls and used them to build up the new walls - so courses 1 to 5 are all in imperial and from then on I switched to using metric blocks.

And yes, it would have been quicker to knock it all down and start again!

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