# Forum Home Renovation Heating & Cooling  double brick wall, how big is the cavity?

## wozzzzza

have to run an aerial wire and rca cables through a double brick wall soon, anyone know how much of a cavity exists in these type of double brick house? will this be an easy task? ive ever run wires through cavities in brick vaneer houses.

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## skot

You should have about 30 - 40 mm gap approx 
Overall width of wall about 250mm less 2 bricks at 110mm wide each

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## GraemeCook

> You should have about 30 - 40 mm gap approx 
> Overall width of wall about 250mm less 2 bricks at 110mm wide each

  
Mine are closer to 100mm. 
I put in an antena cable a couple of years ago using double antenae sockets.   I just drilled a 25mm hole through the skirting board and then through the plaster and inside brick (masonry bit in a hammer drill needed - heaps of dust);  then I put a fencing wire hook through that hole and shon a light into the hole to illuminate the wire.   I then went up into ceiling and dropped a length of fishing line and a small sinker down the wall cavity and moved it along until it rested against the first wire hook.   Back down ladder and pulled the fishing line through the hole in the wall.   Now had the mouse in place to pull the antenae cable through.   Quite an easy job. 
I put antenae sockets in twp rooms - wished I had done more at the time.   You need a TV splitter near the outside antena if you put in more than one wall outlet. 
Cheers 
Graeme

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## skot

Graham, 
If you have a 100mm gap, it is probably for having the room for insulation down there in Hobart , so the overall wall thickness would be greater. In QLD we just need the room to run cables down the middle and create an Air Pocket.

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## autogenous

Cavities vary, standard is 50mm 
They can vary though, brick veneer 30mm ? 
Some walls are 100 as stated for insulation, sometimes 75 
Commercial is about 100mm to take steel etc

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## GraemeCook

> Graham, 
> If you have a 100mm gap, it is probably for having the room for insulation down there in Hobart , so the overall wall thickness would be greater. In QLD we just need the room to run cables down the middle and create an Air Pocket.

  
Nope,  place was built in the 1870's - no insulation in those days. 
Here even modern houses when double seem to always have similar width cavities.   Insulation is very rarely put in such walls.   My guess is that it is to do with ventillation and moisture control. 
Cheers 
Graeme

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## autogenous

> Nope,  place was built in the 1870's - no insulation in those days.

  In that case it could be anything. In fact it may even be 9 inch solid brickwork.

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## wozzzzza

well did the job today, had a nice wall gap of arond 11 cm, could fit most of my arm down it.

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## autogenous

110mm that is a whopper of a residential cavity. Sounds like a 350mm overall wall thickness excluding render?

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## GraemeCook

> In that case it could be anything. In fact it may even be 9 inch solid brickwork.

  
Nope, again.   Exterior walls are double brick with a cavity of about 100 mm, might be 110 like Wozza's.     
Interior walls are 9 inch double brick plus solid plaster.    
Foundations are 18 inch sandstone ashlars. 
Merry Christmas 
Graeme

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## wozzzzza

well what ever it is, i wish my house had cavity that big, theres some things i would like to do but cant due my cavity only being about 4-5cm.

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## rod1949

> Nope, place was built in the 1870's  
> Graeme

  That would have been an escape tunnel :Biggrin: .

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## zacnelson

"theres some things i would like to do but cant due my cavity only being about 4-5cm. " 
I couldn't help laughing at that statement... taken out of context it's hilarious! 
Merry Xmas<!-- / message -->

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