Bricklaying and Blockwork: Why the Trade Behind Your Build Decides How It Ages
The bricklaying is the part of a build you can see for the next fifty years, and it is the part that decides whether the structure stays dry. Mortar mix, cavity detailing, wall ties, damp proof course laps and cavity trays are all set by the bricklayer during the build, and none of them can be corrected afterwards without taking the wall down. That is why the trade behind a build matters more than the finishes.
Key Takeaways
- Mortar mix strength should suit the brick, not simply be made as strong as possible.
- Cavity trays, weep holes and DPC laps are built in as the wall goes up or not at all.
- Wall tie spacing and fall are what stop water crossing a cavity.
- Coursing and perp lines are the visible test of whether the work was set out properly.
- Brick matching on an extension is a sourcing job as much as a laying job.
Bricklaying is our main trade. That is not a marketing line, it is the reason we approach a build in a particular order and the reason we are fussy about details that are invisible once the plaster is on. Over 25 years across Widnes, Liverpool, Runcorn, Warrington and St Helens has taught us which shortcuts come back.
Why does the mortar mix matter so much?
Because mortar is meant to be the weakest part of the wall. Its job is to bed the units, accommodate small movement and, when something has to fail, to fail in the joint where it can be repaired rather than in the brick face where it cannot. A mix that is stronger than the brick reverses that relationship. Moisture and frost then attack the brick itself, and you get spalling, which is the crumbling brick face you see on badly repointed older houses.
So the mix is chosen for the brick and the exposure, not made as strong as it can be. A dense engineering brick in an exposed position takes a stronger mix than a soft handmade facing brick on a sheltered elevation. On older solid walled properties a lime based or lime enriched mix is frequently the right answer rather than a cement rich one. The Brick Development Association publishes technical guidance on mortar selection for exactly this reason.
What is happening inside a cavity wall?
More than most people realise, and almost all of it is built in as the wall rises. A cavity wall is not simply two leaves with a gap. It is a designed system for keeping water on the outside.
| Component | What it does | What goes wrong if it is rushed |
|---|---|---|
| Wall ties | Tie the two leaves together so they act structurally as one wall | Wrong spacing weakens the wall. Ties laid with a fall towards the inner leaf carry water across the cavity |
| Damp proof course | Stops moisture rising from the ground into the wall | Insufficient lap at joints or a DPC bridged by mortar droppings lets damp through |
| Cavity trays | Divert water out of the cavity where it is interrupted, such as above a lintel or where a roof abuts | Omitted trays are the most common cause of damp appearing above openings |
| Weep holes | Let the water a cavity tray collects escape to the outside | Without them the tray fills and the water finds another route inwards |
| Insulation | Provides the thermal performance the building regulations require | Gaps, slipped boards and mortar in the residual cavity cause cold spots and condensation |
| Perpend and bed joints | Bed the units and keep water out of the joint face | Unfilled perps are a direct water path and are visible from the pavement |
None of this can be inspected once the wall is finished, which is why building control inspects at defined stages and why the reputation of the trade doing it carries real weight. It is also why our extension work is sequenced so the masonry is not rushed to hit a date.
How do you match brickwork on an extension?
Matching is a sourcing exercise before it is a laying exercise. Four things have to line up.
On genuinely old or unusual brick an exact match is not achievable, and we say so at survey stage. The options are then reclaimed stock, a close modern equivalent accepted as a deliberate contrast, or a design that separates new from old with a recessed joint so the junction reads as intentional. Our guide to brickwork restoration and repointing covers matching on repair work.
How can you judge finished brickwork yourself?
You do not need to be a bricklayer to spot good work. Stand at the end of a wall and look along it. The bed joints should run dead level and the perps should line up vertically in alternate courses, with consistent joint thickness throughout. Look at the joint faces: they should be filled and finished the same way across the whole elevation, with no missing perps. Look at the reveals around openings, because that is where setting out errors show up as tapering joints.
On a cavity wall look for weep holes above openings and at the base of the wall, which tell you cavity trays were fitted. Look at where the wall meets the ground for a visible DPC at least 150mm above finished ground level. Look at whether mortar has been kept off the brick faces, since heavy smearing usually means the work was rushed. And on an extension, look at the junction with the existing house and check whether the courses line through.
Building regulations set the performance requirements the wall has to meet, and GOV.UK sets out the approval process that verifies them. The visual checks above tell you about workmanship, which is the part that regulations cannot police on your behalf.
Frequently Asked Questions
Is bricklaying really different from builder to builder?
Substantially, and it shows up in two places. Visually, in whether the coursing runs level, the perps line up and the joints are consistently finished. Functionally, in whether the cavity detailing, wall tie spacing and DPC laps were done properly. The second matters more and is the part you cannot see, which is why the trade behind the build is worth asking about.
Can bad brickwork be fixed later?
Cosmetic issues such as poor pointing can be raked out and redone. Structural and weathering issues generally cannot, because wall ties, cavity trays, weep holes and DPC laps are built into the wall as it rises. Correcting a missing cavity tray after the event usually means taking down the masonry above the opening, which is why getting it right first time is not a small point.
What is spalling and why does it happen?
Spalling is when the face of a brick crumbles or flakes away, exposing the softer material inside. The usual cause is moisture in the brick freezing and expanding, and the usual reason the moisture is there is a mortar mix harder than the brick, which forces water into the brick face rather than the joint. It is very common on older houses repointed with a cement rich mix.
Do you do blockwork as well as facing brick?
Yes. Most modern cavity walls are a facing brick outer leaf and a blockwork inner leaf, and internal load bearing walls are frequently blockwork. Both are part of the same trade and both need the same attention to coursing, joint filling and tie positions. Blockwork being hidden is not a reason to build it carelessly.
How long does the brickwork stage take on an extension?
On a typical single storey extension, brickwork from damp proof course to plate level is usually two to four weeks depending on size and the amount of detailing around openings. Weather affects it, since mortar should not be laid in freezing conditions, but the practical effect in the North West is normally a day or two rather than a stopped programme.
Do you take on bricklaying as a standalone job?
We do masonry work as part of the projects we manage, which covers property extensions, structural alterations, and interior and exterior remodelling, along with residential and commercial renovations. If your job is masonry only, such as rebuilding a damaged section of wall as part of wider renovation work, that fits comfortably within what we do.
The part of the build that lasts longest
Finishes get changed every fifteen years. The masonry is there for the life of the building, and it decides whether the wall stays dry.
We provide free designs and quotes across Widnes, Liverpool, Runcorn, Warrington and St Helens. Our case studies are the best way to judge the standard of the work.