On Monday, 27 August 2012 20:25:55 UTC+1, RJS wrote:
The cause of a loose socket has been traced to loose bricks (or their remains). The socket pattress was held loosely in by plaster around its edges..



As the fragments of brick were doing nothing more than sitting on the cavity wall foam I have removed them.



I now have a rather intimindating void to fill.



Do I (a) re-fill the hole with brick that must be shaped to fill the hole, (b) ditto but with easily shaped lightweight block rather than brick or (c) contrive suitable shuttering and fill the hole with concrete.



A and B are least appealing because of the difficulty of properly filling the crevices with mortar when pointing in the new brick(s) and the difficulty of cutting them to fit. C is most appealing because of its gap filling properties.



TIA



Richard

I have replaced bricks in a cavity wall before. The brickwork forms a 'corbelled' arch if you don't take out too many bricks horizontally at the top. Probably you don't want to take out more than one brick at the top though maybe you could take out the two directly beneath it if they need replacing, but you want to form a fairly tall 'arch' as it were, not a very flat arch.. You need to do your own homework on that.

Knock out damaged bricks if it is safe to do so then lay new ones in the usual way - the only difficult one is the one at the top - using mortar (soft sand + cement, maybe 5:1 or so).

The top brick lay the brick in the void on a base of mortar laid in the normal way, chop in needs a rather stiffer mix (less water) to fill the mortar joint above the brick else as you puch mortar into the joint it'll all fall out the back into the cavity.

This takes a little technique not to push it all out the back and down the cavity. Maybe sharp sand would help instead of soft (I used sharp). You find the mortar will 'lock up' at the back of the mortar joint if you are careful and you just gently pack more in with an appropriate bit of wood until the top mortar joint is filled.

You *could* make up a sort of tool to back the mortar joint if that doesn't work for you, even just a bit of mesh pushed to the back of the joint, lots of different possibilities...