How To Square New Building Walls

[EViS]

We are about to start constructing the cavity walls of our 9mx9m outbuilding where only the front and one half of a side wall (which currently adjoins the front wall) is being retained. We quite crudely measured out our 700mm wide footings off these existing walls, but now need to make sure the new walls are dead square and level.

Without a laser level, what's the best technique to get our first course of blocks down onto the footings to run square and level all the way around. I would imagine that the footing isn't going to be mm level from one corner of the site to the other and will not be dead square either.

In the below sketch, the black lines are the new footings and in red are the existing walls.

Untitled

• EViS
• 6 Dec 2014
• 1

 

[theprinceofdarkness]

From the corner B mark of along towards A a distance divisable by 3 , say 3.6m (Z). From B towards C mark of a distance 1 1/3 time Z which in this case is 4.8m. If the corner at B is true, the the two marks will be 1 2/3 times the distance measured on A = 6.0m. The ratios of the sides will be 3 : 4 :5.
The best way is to use corner A as a start to get the angle towards B, Then corner C to get another corner B. Then figure out what to do? This will reflect how good angle the old corner A is.
Use a water level? Or just use bricks and bits of wood and vinyl flooring and a 2m level to carry a level from corner A to D in both directions. If there is a bad error, try a direct diagonal a to D?

Frank

 

[Alastairreid]

http://www.wikihow.com/Use-the-3-4-5-Rule-to-Build-Square-Corners

 

[jeds]

Mark out corners as close as possible using a square. Check diagonals and adjust accordingly.

 

[EViS]

That all makes perfect sense and easy to follow. How about making sure that the first course of blocks is level all around? Is a water level or bricks/timber the easiest and accurate solution?

 

[jeds]

Hire or borrow a device. Or you could make a water level from a hose pipe and some clear tubing.