Help! - Advice on my wall and plasma mount!

[MattMcSpirit]

Hi Guys,

The lounge redevelopment is underway, and I hoped someone could advise me on my wall, which is the wall between our place and the neighbours house, as I'm a little confused! The house is about 25 years old.

Basically, I was channelling into the wall, and went through the following layers:

Top 3mm - I presume is finishing skim plaster - chipped off easily after I scored the edges of my channels.
Next 10mm approx - quite brittle, light grey-coloured material -plaster I presume?
Next 25-30mm approx - sandy coloured material, took a while to chip through, but scrapes off quite easily and creates quite a lot of sandy dust...

Anyway, I wasn't planning to go so deep, but I managed to make a small hole by accident, going through the sandy coloured material. I expanded the hole a little to check what was behind there, and if I put my screwdriver through the hole, there was an air gap of about 40mm, with a hard surface on the other side.

If it was breeze block, I would assume the air gap would be double what is there. I tried drilling some holes in a few other places too, and with a 50mm (in length) drill bit, and it passed through the layers as described above, and hit the air gap as expected.

The question is, what kind of walls do I have, and what will be the best way to fix my 42" plasma to the wall? I currently have 60mm concrete anchors, with 60mm fixing screws, both of which were supplied with the bracket.

Any advice would be great,

Thanks guys,
Matt

[MattMcSpirit]

I've been told it could be thermal block - does this seem right?

[ched]

Sorry I dont know the answer but a total of 50mm does seem very narrow for a complete wall. Most blockwork I have seen is normally about 100mm and thats just the blocks! It might be worth taking a photo and popping down your local friendly builders merchants as they should be able to tell you what the blocks are and maybe even the best way to fix your bracket to it.

[stevey27]

wont be thermal block, the solid bit your hitting will be brick which in turn should have a cavity then brick again on the other side (the neighbours side) if your unsure cut 1 6" x 6" hole to see what the first air space is for

[mortimar]

It would be good to see a picture . The only blocks I can think of that are a sandy colour that have voids in the are of a Terracotta nature see link

http://www.fbt.ie/technical.html

I have also used Cellular Concrete Blocks which are generally 100mm thick . They can have 4 or 5 voids in a standard block . Which would give from memory a 40mm void

[MattMcSpirit]

Thanks guys,
I've got a builder mate coming around this weekend to have a look, but in the mean time, I think that the wall is 50mm, then 40mm air gap, then brick, then another 40mm air gap, then 50mm for the neighbours internal wall. Would that make sense?
Matt