Wotcha all, I’m having an extra skin put on the 2 storey single brick gable end wall of my house. The quote was for 7n thermalite blocks then rendering. The semi crazy patriarch of our road has just sent me word via my sister that “they’m using the wrong bricks, I’ve told ’em, but they says the regs have changed”

I’m guessing from this that it means they’re using the 3.6n blocks, as the pattern on them still suggests they’re Trenchblocks. I’m just looking for all the relevant info before I chat to the builders so that I’m less easy to confuse and fob off. I gather the 3.6 ones are more porous or somesuch – old Frank’s saying that a pinhole in the render and they’ll suck up the rain. If they are using 3.6 am I best to demand they take it down and do it with the ones as quoted, or will they be functionally fine and I just renegotiate the price (presuming the reason for different blocks was to save cash.

Thanks for any help, I’m completely out of my depth here

The building design docs you submitted to Building Control will state the type of block to be used. If you use the wrong ones potentially the wall won’t be able to take the load and you could get forced to remedy it by BC (knock it down and rebuild). The 3.6/7.2 is the load bearing ability of the block.

If in doubt phone Building Control, they’re normally very helpful.

I’d never use thermalites to render on to.

http://singletrackworld.com/forum/topic/alternative-to-thermalite-building-blocks

Cheers, all. Seems I need to tell chappy his brand choice is shit. Will talk to the bloke up the road tonight and building control fellow in the morning and try to figure out what questions I should be asking and what results I should be expecting. And it all seemed to be going so smoothly too…