Compressive Stress Values for Bricks and Blocks

Sounds like breeze blocks. I would treat them as 2.8N/mm2 blocks (this is the crushing strength: the actual stress you can put on them is a lot less than this)

Fletton near Peterborough was the place where the clay used to make them was first found. It contains shale that burns during the firing process thus reducing the amount of fuel required significantly (and this making the bricks cheaper). On spec housing they are generally laid frog down (to save mortar) so should be treated as 7N. Laid frog up the full 21N crushing strength can be assumed.

Lots about Fletton bricks in a (PDF) Competition Commission report at

Tony

Thanks for comprehensive reply!

One or two points arising:

Yes, now you mention them, the term breeze blocks is familiar - pretty sure that's what I'm dealing with. How can I use 2.8 N/mm2 for these, if the actual capacity is a lot less? Do you have reference links/texts for figures quoted? What is spec housing?

Phil

"Tony Bryer" wrote

Basically by reference to BS5628: the net allowable stress will be a function of the block material (as above), thickness, mortar, bearing type and assumed standard of workmanship. 0.7N/mm2 should be a safe conservative figure for 100mm blocks.

Thanks Tony Much appreciated

Phil