Lay bricks properly

Cue 1 Two walls side by side: soft mortar cracking in the joint, hard mortar spalling the brick face.

AMARA 00:00 I would have guessed that more cement means a stronger wall.

NADIA 00:04 Everybody does, and it is the most expensive mistake in domestic bricklaying. Mortar is supposed to be weaker than the brick.

AMARA 00:12 Weaker? Deliberately?

NADIA 00:13 Deliberately. Mortar is a sacrificial material. Every wall moves, with temperature and with moisture. You want that movement to crack the mortar joint, because a joint can be raked out and repointed by anybody for very little money.

Cue 2 Victorian wall with blown brick faces after hard repointing.

AMARA 00:28 And if the mortar is stronger than the brick?

NADIA 00:32 Then the brick cracks instead. And now you are not repointing, you are cutting out and replacing bricks in a wall, which is a different job and a different bill.

AMARA 00:44 Is that why so many old houses look like the brick faces are falling off?

NADIA 00:50 Precisely why. Somebody repointed a soft Victorian handmade brick with a hard modern cement mortar. The wall could no longer move or breathe, moisture got trapped behind that hard pointing, it froze, and the face of the brick blew off. You can drive down any street and see it.

Cue 3 Bucket gauging beside shovel gauging, with the resulting colour banding.

AMARA 01:10 So what mix do I use?

NADIA 01:12 For most external brickwork in ordinary exposure, one part cement, one lime, six sand. Softer or handmade bricks and older solid walls want one, two, nine, which is gentler still.

AMARA 01:24 And when do I go stronger?

NADIA 01:26 Where it gets wet and freezes. Below the damp proof course, freestanding garden walls, copings, parapets. There you want one, half, four and a half. Everywhere else, resist the urge.

Cue 4 Trowel drawn through mortar holding a peak, then too wet, then too dry.

AMARA 01:38 What about sand? Sand is sand.

NADIA 01:41 It really is not. Use building sand, which people also call soft sand. Sharp sand is for concrete and screed, and if you lay bricks with it you will get a harsh gritty mortar that tears off the trowel and fights you all day.

AMARA 01:58 How do I get consistency between batches?

NADIA 02:01 Gauge by bucket, never by shovel. A shovel varies with who is holding it and how tired they are, and by four in the afternoon it is a different measure entirely. Same bucket, count it out.

Cue 5 Cement burn progression on skin over hours.

AMARA 02:16 Why does that matter so much?

NADIA 02:18 Because a wall built from batches that varied will dry with visible colour banding across it. It looks like stripes and there is nothing you can do about it afterwards.

AMARA 02:30 How do I know it is the right wetness?

NADIA 02:34 Draw the trowel through it. It should hold a peak, cling to a vertical trowel face for a moment, then slide off cleanly. If it slumps flat it is too wet. If it tears and crumbles it is too dry.

Cue 6 Dry cutting dust cloud beside water suppressed cutting.

AMARA 02:50 Last thing, and I want you to be blunt. What is the danger?

NADIA 02:55 Two, and both are underrated. Wet cement causes chemical burns, and because it is painless at first people kneel in it or let it sit inside a glove and end up in hospital with full thickness burns. Waterproof gloves, and wash it off immediately.

AMARA 03:12 And the second?

NADIA 03:13 Silica. Cutting bricks and blocks dry with a grinder throws out enormous quantities of respirable crystalline silica, and it causes silicosis and lung cancer. Water suppression or on tool extraction, and proper respiratory protection. It is the most serious long term risk in the entire trade and it is the one you will see ignored on almost every site you walk past.

Cue 1 Brick dimensions with the 10mm joint added, showing 225 and 215 resolving.

AMARA 03:38 Why is a brick the size it is? It looks completely arbitrary.

NADIA 03:43 It looks arbitrary until you add the joint. A standard brick is 215 long, 102.5 wide, 65 high. Add a 10mm joint to the length and you get 225.

AMARA 03:55 And the width?

NADIA 03:56 Two widths plus a joint. 102.5, plus 102.5, plus 10, gives 215. Which is exactly the length of a brick.

Cue 2 Gauge rod against a wall with four courses to 300mm marked.

AMARA 04:04 So a brick laid across the wall is the same length as one laid along it.

NADIA 04:10 That is the whole system. Without it, bonding is impossible. And the height does the same thing: 65 plus 10 is 75, so four courses rise 300mm exactly. That is your gauge, and it is the number you check against all day.

AMARA 04:27 Where do people go wrong?

NADIA 04:29 The first course, almost always, and nothing you do afterwards rescues it. If the bottom is out, you spend the rest of the wall cutting bricks and fudging joints to hide it, and it shows anyway.

Cue 3 Dry set out of a first course with the end gap being distributed.

AMARA 04:44 So what do I do before I mix anything?

NADIA 04:47 Set it out dry. Lay the entire first course on the foundation with no mortar, leave 10mm gaps, and see where it lands.

AMARA 04:56 And if it does not come out even?

NADIA 05:00 Then you adjust the joint widths very slightly across the whole run. A millimetre here and there across twenty bricks is invisible. What you must not do is take up the whole error in one place and cut a horrible little slip of brick at the corner, because that is the first thing anyone's eye will land on for the next fifty years.

Cue 4 Ends built and racked back, string line running between them.

AMARA 05:25 How do I keep a long wall straight?

NADIA 05:28 You do not try. Build the ends first, several courses high, racking them back so they step. Then run a string line between them at the top of each course and fill in between.

AMARA 05:42 That feels like more work.

NADIA 05:44 It is far less. Keeping two small stacks accurate is easy. Keeping thirty bricks in a line accurate by eye is not, and every professional on every site does it the first way.

Cue 5 Load path spreading sideways through a bonded wall, then running straight down a straight joint.

AMARA 05:57 Tell me about the bond itself.

NADIA 05:59 Stretcher bond, which is what almost every modern outer skin is. Each course offset by half a brick, so every brick spans the joint below it.

AMARA 06:10 Why does the offset matter structurally?

NADIA 06:12 Because a load coming down spreads sideways into the bricks either side instead of running straight down one continuous vertical joint. Line those joints up and you have a straight joint, which is much weaker and looks wrong the instant anybody glances at it.

Cue 6 Four bonds side by side: stretcher, English, Flemish, English garden wall.

AMARA 06:30 And how do I make the offset at the end of the wall?

NADIA 06:35 A half bat. A brick cut in half across its length, starting every other course. That is what produces the stagger, and it is the first cut most people ever make.

AMARA 06:47 Any other bonds I should know?

NADIA 06:50 Three worth recognising. English bond alternates whole courses of stretchers and headers, and it is very strong. Flemish alternates them within every course and it is the handsome one you see on Georgian houses. And English garden wall bond runs three or five stretcher courses to one header course, which uses fewer facing bricks. Which tells you exactly why it ended up on garden walls.