Brick up a window like a pro
insulation value. In the post-war building boom, cavity walls became the norm, later adding insulation in the cavity to give the walls we have as standard now. You can tell the difference quite easily. If the outside wall is 22-25cm deep, it is most likely a solid wall construction. This means the wall is two bricks thick, so you’ll need to use double the amount of bricks if you’re counting them from the outside. If the wall is closer to 30cm thick, it is most likely a cavity wall, in which case you’ll need to count the number of bricks on the outside skin and build the internal skin with breeze blocks. The gap between the breeze blocks and the bricks makes the cavity.
3. Are the bricks imperial or metric sizes? When we changed to the metric system in the 70s, our brick sizes changed too. Old imperial bricks were 9 inches by 4 1/4 inches (225x107.5mm), new metric bricks are 215x102.5mm. They are not compatible, so measure your bricks before you go buying. You can buy both types from most building suppliers, but imperial are often harder to match for colour.
4. For bricking up a window, is there a concrete lintel (horizontal support) and do you want to keep it? Windows are vulnerable points in walls that would weaken the brick work if they weren’t supported by lintels or arches. In cavity wall construction, you will most likely have a steel lintel with a facing brick on the front of it that matches or complements the rest of the wall – leave this in.
If you have a concrete lintel over your window, you have the option of taking it out and re-filling the space with bricks. Now lintels are deceptively heavy, so be careful. Do not attempt to take one out without professional advice if your window is more than 70cm wide. If you do want to remove the lintel, I’d wait until you’ve laid bricks up to within two courses of the top of the window. Then, use a masonry drill bit mounted in a hammer drill to carefully rake out the mortar surrounding the lintel. Avoid hitting your wall with a hammer, as this will dislodge some of the bricks that the lintel is holding back.
Once the lintel is free, take it out and continue building up to the top. Even with the most skillful of raking out, you may still dislodge a couple of bricks above the lintel. Knock off the mortar from these and build them back into the wall.
The tools you’ll need: Hammer, wood chisel and panel saw (to get the old window out); a brick trowel; pointing trowel; some string; a few masonry nails; a club hammer; a bolster (for cutting bricks); a hammer drill with a masonry bit; a shovel; a bucket; an area for knocking up mortar; a jointing tool, or a small piece of 15mm copper pipe; a soft brush – paint brush or dustpan brush will be fine; PPE Gloves, and goggles.
The materials you’ll need: Bricks (counted by using the rest of the wall as a guide – remember to use double if it’s a solid wall); breeze blocks if required; cement – one 20kg bag per 0.75m2 of a single skin brick wall. Remember, cement is the grey dusty stuff and mortar is cement + sand + water; soft sand (sometimes called building sand) 2x25kg bags per 0.75m2 of a single skin brick wall, and plasticiser – an additive that makes the mortar easier to use.