How do I lay bricks so the wall comes out level and plumb?

The reason amateur brickwork looks amateur is almost never the mortar. It is that the joints get progressively thicker or thinner along the wall, and the face is not in one plane. Both problems are solved by the same method, which is that you build a small amount very accurately at each end and then use a string line to transfer that accuracy across the whole wall. The drawing shows the gauge rod, the racked-back corners and the line, and what a correct bed and perpend look like next to a bad one.

What you'll need

• A 1200mm spirit level
• A brick trowel
• A line and pins or corner blocks
• A gauge rod marked at 75mm intervals
• A level, cured concrete foundation
• A club hammer and bolster for cuts
• A jointing tool for the joint profile you want

Step by step

1. Make the gauge rod first.A straight batten longer than the finished wall height, marked every 75mm from the top of the foundation — 65mm brick plus 10mm joint. If the bricks are a non-standard size, measure them and mark the rod to suit.
2. Set the first course out dry.Lay bricks along the foundation with a 10mm gap between them, without mortar. It tells you whether the length works out in whole bricks, where the cuts have to fall, and how the bond arranges itself around any opening or return.
3. Build the corners first, racked back.Build each end up several courses, stepping back one brick per course so it forms a staircase. Everything about the wall's accuracy is decided here, so take as long as it needs.
4. Check the corner three ways at every course.Level along the course, plumb up the face, plumb up the return, and against the gauge rod for height. Correct now, while the mortar is soft. A corner one brick out at the third course is a wall that is out for the rest of its height.
5. Stretch the line between the corners.Line pins driven into a joint at each end, or plastic corner blocks hooked over the brickwork, with the line pulled taut at the top edge of the course you are laying. Set it a couple of millimetres clear of the brick face so it does not touch and drag.
6. Lay the bed properly.Pick up mortar on the trowel, roll it onto the wall in a bed about 15 to 20mm thick before compression, and furrow the middle lightly with the trowel point. Do not spread the bed so far ahead that it dries out.
7. Butter the perpend on the brick, not the wall.Put mortar on the end of the brick before you lay it, in a wedge, and push the brick up to its neighbour so the joint squeezes full. This is the step people skip and it is why so much amateur brickwork has hollow vertical joints that let rain in.
8. Tap the brick down to the line.Lay it, then tap it down with the trowel handle until the top edge is level with the line and just clear of it. Aim for a joint of about 10mm once compressed. Never pull a brick back up once it has been bedded — take it off, clean it, and re-lay it with fresh mortar.
9. Cut the squeezed mortar off cleanly.Run the trowel along the face at an angle to cut off the extrusion, and return it to the board. Do not smear it up the brick face, which stains it and is very hard to remove once set.
10. Check every few bricks, not every brick.The line does the levelling. Check plumb across the face with the level every metre or so, and check the gauge at each corner as you rise.
11. Joint up when the mortar is thumbprint firm.Too soon and the jointing tool drags the mortar out; too late and it will not compress. Test with a thumb: it should take a print and hold it. Do the perpends first, then the beds, so the horizontal lines run through cleanly.
12. Brush the face off after jointing.A soft brush over the whole face once the joints have firmed further, to remove the crumbs left by the jointing tool. Brushing too soon smears mortar into the brick and stains it.
13. Protect the work overnight.Cover the top of the wall and the new face against rain and frost, holding the sheet clear of the face on battens.

Tips

• Mix a batch you can use in about an hour. Mortar that stiffens on the board and gets retempered with water is weaker, and it changes colour as well.
• Reverse your spirit level end to end on the same spot occasionally. If the reading changes, the level is out and everything you have built to it is out with it.
• On a garden wall, work out where a movement joint should go before you start rather than after, and set out the bond to suit.
• Keep the mortar off the face from the beginning. Cleaning brickwork afterwards is far harder than not staining it.

Common mistakes

• Building a long wall course by course from one end — Without corners and a line there is nothing to hold the accuracy, so the courses drift and the joints thicken to compensate. The method is not slower — it is what makes the job possible.
• Adjusting a brick after it has started to stiffen — Moving a bedded brick breaks the bond that has begun to form and it never recovers. Lift it, clean both surfaces, and re-lay it in fresh mortar.
• Letting the line touch the brickwork — The line stretches and drags against the face, so it no longer runs straight and every brick after that point is laid to a curve. Keep it just clear.
• Smearing squeezed mortar up the face — It stains the brick and, once set, cannot be cleaned off without acid or abrasion. Cut it off cleanly and put it back on the board.