If you're removing a load-bearing wall from a building, you'll need to brace the structure correctly. Failure to do so risks losing the brickwork above the cut-out you intend to do -- or even worse, the partial collapse of a complete wall. Most load-bearing walls are of a cavity construction measuring 100 mm of brick, a 50 mm cavity and 100 mm block, giving a 250 mm overall thickness. When preparing to remove any kind of load bearing wall it is imperative to make sure the remaining wall above the brick work you intend to remove will stay in place. By taking your time and using the correct methodology, disaster can be averted.
Clearly mark the vertical and horizontal lines of the brickwork to be removed using a chalk line.
Ascertain the thickness of the wall to be removed. This can be measured at the door or window reveal from outside to inside; deduct 15 mm for plaster to find the thickness. Load bearing walls are normally 250 mm thick.
Measure 230 mm down your drill bit from the tip and wrap some electrical tape around the drill at this point. This will be used as a depth marker when stitch drilling.
From the top horizontal chalk mark go up 3 courses of bricks and mark another horizontal line on the mortar joint that extends past the two vertical lines by approximately 200m either end.
Stitch drill a slot at the beginning of the new line approximately 200 mm wide to the depth of the tape mark on your drill bit. Use the drill at an angle to clear all the mortar from the slot leaving a 200 mm slot that is 230 mm deep. This will go through the first skin and into the second skin of the brick work. Ensure the middle of this slot lines up with a perp joint in the brick course above the slot (a perp joint is the vertical mortar line between two brick ends).
Repeat the process in the last step roughly every 500 mm along your new horizontal chalk mark until you have a series of slots in the wall above the line of your brick work removal. Ensure that you have a slot at the end of your marked line.
Lay a long scaffold board on the floor approximately 200 mm from the face of the brick work. With a helper, stand the first Acrow prop in line with the first slot, connect a strong boy to the top of the Acrow prop and push the Strongboy blade into the slot as far as it will go. Tighten the Acrow prop until the Strongboy grips against the brickwork above. Repeat this process for every slot you have drilled out. Ensure that the centre of the Strongboy blade sits in-line with the perp joint above.
Tighten all Acrow props along your slotted line to take the weight of the load bearing wall above. As a safety measure, hammer a 100 mm nail through the base plate of each Acrow prop and bend the nail over to stop the Acrow prop from slipping. You are now ready to remove your brickwork.
The Strongboy blade is situated under a perp joint to spread the load from above by resting two bricks on the single blade creating an inverted triangle to spread the load.
There are specialist tools available from most hire shops for cutting slots in mortar joints.
Before drilling any holes, ensure there are no buried wires or pipes.