Bricklaying Question

How many blocks do i need to build a extension 3.5mx3.5m x 2.4mhigh with a cavity

7 Answers

Best Answer

Hi, the amount of blocks you would need ,would be 588. its 10 blocks per square metre.

3.5 x 3.5 = 12.25m (lenth)
12.2 5x2.4 = 29.4 m (lengh x height)
29.4 x 2 = 58.8 m (x2 for cavity so two skins)
58.8 x 10 = 588 blocks (x10 -10 blocks per squre metre)

Also add 5% for wastage.

Answered 28th Feb 2011

ace plastering & building services

Member since 5 Jan 2009

standard blocks are 450mm x 225mm high so its 10 to a square mtr. so i expect your extention has 3 side so 3.5 trs x 2.4 mtrs = 8.4 mtrs x 10 blocks = 84 blocks x 3 walls = 252 blocks skin x 2 = total 502 blocks. and then you need to take away the area of your windows and door.
hope this helps you.

Answered 28th Feb 2011

tom harveyassociates

Member since 30 May 2010

I would agree with Tom .
If you get the higher amounts at least you will have some spare blocks to sit your spot boards on.

Answered 1st Mar 2011


Member since 29 Oct 2008

520 blocks will cover the job ,

Answered 28th Feb 2011


Member since 7 Jun 2008

you would need 50.4 metres=504 blocks less windows and doors

Answered 10th Mar 2011

dpc builders

Member since 18 Nov 2010

If i was you i would add another
3.5 +3.5 +3.5 =10.5 length
0.9 depth of footing (depending on ground conditions)
sub total =9.45 x 2 skins =18.9m2
@10 block m2 =189 without waste
call it 3packs @ 72= 216 allowing for waste,

unless your not having any footings on your extension.
Even better get someone who knows what they are doing to come round and have a measure up unless it probably will cost you in the long run.

Answered 19th Mar 2011

SS Masonry

Member since 20 Feb 2009

10 blocks per m2

Answered 18th Mar 2011

Coates Construction

Member since 26 Nov 2010

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