Common Mistakes When Building with Cement Bricks and How to Avoid Them

Executive summary

Cement brickwork failures rarely come from a single “bad brick.” Most defects are created on site through avoidable errors: incorrect mortar batching, weak bonding practices, inadequate curing/protection, poor damp-proof detailing, wrong strength (MPa) selection, and careless handling/storage. These mistakes usually show up later as cracks, damp patches, efflorescence, staining, joint failure, or uneven settlement—and they can become costly disputes because workmanship and compliance obligations typically sit with the contractor/builder.

This post summarizes the most common on-site mistakes, explains why each matters (structural, durability, and legal/dispute risk), and gives clear prevention steps and supervisor checklists. It also includes short recommended specifications (10 mm joints, curing windows, and MPa guidance) aligned with authoritative sources.

Note on sources: Some widely used masonry workmanship guidance comes from the Brick Industry Association (BIA). BIA technical notes are written specifically for fired clay brick and caution that applying them to non-clay products (including concrete brick) may not yield the same performance. Use them as workmanship principles, but always follow project specs and South African standards first.

Recommended site specs for cement brickwork

These short specs are practical “defaults” for most small-to-mid projects unless an engineer/project spec requires something else.

1. Mortar selection and batching

• South African deemed-to-satisfy wall provisions reference Class II mortar complying with SANS 2001-CM1 for common masonry wall scenarios.

• Keep mortar workable but do not “water it up.” AfriSam warns that excessive water reduces strength and that mixes must not be retempered by adding water later.

• Use mortar within the workable time window. AfriSam states mixes should be used within two hours and not retempered; BIA guidance similarly sets time limits (shorter in hot weather).

2. Joint thickness

A common South African project specification requirement: mortar beds 10 mm, not exceeding 12 mm, with brickwork laid in stretcher bond.

3. Curing and protection

• AfriSam recommends keeping concrete/mortar/plaster protected from sun and wind and kept moist for a minimum of 7 days.

• For hot weather, recommended practices include fog-spraying newly constructed masonry multiple times daily until the masonry is about three days old; for cold weather, newly constructed masonry is protected/covered after completion for specified periods.

4. MPa guidance

• SANS 10400-K provides compressive strength minimums (deemed-to-satisfy) that vary by wall type and building scenario. Examples include:

  • For some single-storey/upper-storey cases: average compressive strength not less than 3 MPa (hollow) and 4 MPa (solid).

  • For lower storey of certain double-storey buildings: not less than 7 MPa (hollow) and 10 MPa (solid).

  • For certain free-standing/retaining/parapet/balustrade walls: not less than 3 MPa (hollow) and 5 MPa (solid).

• In the South African market, concrete bricks are commonly manufactured to standards like SANS 1215 and offered in strength classes (e.g., 7 MPa or 14 MPa depending on application).

  
  

The most common on-site mistakes and how to prevent them

Below are the top mistakes seen across residential, RDP, boundary wall, and small commercial work. Each mistake is paired with why it matters and what to do differently.

Mistake-to-impact table:

	Mistake	What it causes on site	Prevention that works
1	Over-sanded or over-watered mortar	Poor bond, weak joints, leakage paths, early cracking	Accurate batching; use only enough water for workability; don’t “revive” mortar with water later
2	No curing/protection after laying	Dusty/weak joints, shrinkage cracking, poor durability	Keep masonry moist and protected (minimum 7 days); hot-weather fog-spray; cover in cold conditions
3	Poor storage (on ground/uncovered)	Contamination, staining, efflorescence risk, breakage	Store off ground; cover with water-resistant materials; protect unfinished walls from rain
4	Wrong MPa selection	Structural noncompliance, cracking, failure risk	Select MPa by wall type and storey per SANS 10400-K; confirm with engineer for higher loads
5	Poor bond pattern / weak returns	Cracking at corners, “unzipping” of wall, weak panels	Stretcher bond to line and level; set out bond at first course; don’t use false headers
6	Inadequate foundation/ground prep	Settlement cracks, door/window distortion, disputes	Foundations must comply with relevant standards; don’t build on poorly prepared base
7	Bad damp-proofing (missing/bridged DPC)	Rising damp, salt movement, interior damage	Install DPC at top of slab; keep ≥150 mm above adjacent ground; avoid plaster bridging DPC
8	Poor joint workmanship (unfilled/perpends, “slushing”)	Water penetration, efflorescence, weak bond	Fully fill joints; avoid slushing head joints; tool joints correctly (concave/V)

1. Incorrect mortar mix ratios and bad batching controls

Why it matters: Mortar is the bond that turns individual bricks into a wall system. If mortar is harsh (over-sanded), too wet, or inconsistently batched, you reduce bond strength, increase shrinkage risk, and create leakage paths through joints. BIA guidance highlights oversanding as a common cause of harsh, unworkable mortar and links it to poor bond strength and water penetration risk.

Prevention steps

• Batch consistently (same container sizes; no “random shovels”). BIA explicitly recommends accurate batching and using the maximum water that still produces workable mortar.

• Use only enough water for workability—AfriSam warns excessive water reduces strength.

• Do not retemper by adding water later; discard mortar that has begun to set.

  
  

Quick spec to issue to your team

“Use within 2 hours; do not add water after stiffening; keep mix workable, not wet.”

2. Poor curing and inadequate protection after laying

Why it matters: The first 24–72 hours are when cement-based materials are most vulnerable to rapid moisture loss (hot wind/sun) or freezing (cold snaps). Poor curing reduces strength, increases surface dusting and cracking, and can permanently weaken joints.

Prevention steps

• Keep work protected from sun and wind and keep moist for at least 7 days (AfriSam).

• In hot weather conditions, use added protection such as fog-spraying multiple times per day during early age.

• In colder conditions, cover/protect newly constructed masonry after completion for the required period.

3. Improper storage and contamination on site

Why it matters: Bricks and sand stored on the ground pick up moisture, dirt, and soluble salts (a key ingredient for efflorescence). BIA’s efflorescence guidance recommends storing masonry materials off the ground and covering them to prevent groundwater and precipitation exposure.

Prevention steps

• Store bricks, cement, sand, and accessories off the ground and under cover.

• Cover sand/aggregates to avoid saturation and segregation.

Protect unfinished walls at the end of each workday (cover down from the top so rain cannot enter cores/joints).

4. Wrong MPa selection for the application

Why it matters: If the brick MPa rating (compressive strength) is too low for the wall type/storey load case, the wall may not meet deemed-to-satisfy requirements, and cracking or structural distress risk increases. SANS 10400-K gives minimum average compressive strengths that vary by wall application (single storey vs lower storey; free-standing walls; etc.).

Prevention steps

• Decide early: Is the wall loadbearing? Is it in the lower storey of a double-storey building? Is it a free-standing boundary wall? Map the wall type to the correct compressive strength minimum per SANS 10400-K.

• If your structure exceeds deemed-to-satisfy limits (span loads, panel sizes, unusual exposure), appoint the engineer and build to the engineer’s schedule.

  
  

5. Bad bonding practices and weak wall “geometry”

Why it matters: Many cracks come from poor set-out, weak corners/returns, and bond patterns that don’t properly interlock. Local specifications often require stretcher bond and correct bond set-out at first course.

Prevention steps

• Set out bond from the first course; keep perpends plumb and courses to gauge.

• Use stretcher bond as specified and avoid “false headers” where prohibited.

• Stop work by stepping back courses (don’t leave a straight vertical break).

  
  

6. Poor joint workmanship and “slushed” head joints

Why it matters: Exterior durability is often decided by joint quality. BIA workmanship guidance stresses completely filled joints, prohibiting head-joint slushing, and recommends tooling joints (concave/V) for exposed work.

Prevention steps

• Butter ends properly and fully fill perpends (head joints). Local specs commonly require joints to be flushed/solid throughout.

• Tool joints at the right time (thumbprint hard) with concave or V tooling for better weather resistance.

• Avoid raked joints in high-exposure work unless specifically detailed—raked joints are generally not recommended in heavy rain/high wind exposure in masonry guidance.

7. Inadequate foundations, ground prep, and rushing in wet weather

Why it matters: Settlement and water management failures create long-running defect disputes (cracks, damp, doors not closing). SANS 10400-K requires that the foundation design complies with the relevant foundation standard references for deemed-to-satisfy wall solutions.

Prevention steps

• Build only from a verified founding level and compliant foundation (don’t “make it work” with extra mortar).

• Manage sequencing: many specs also limit how much higher one section can be built relative to adjacent work to reduce differential movement/cracking.

• Stop masonry during heavy rain exposure and protect unfinished tops—water entering the wall during construction increases efflorescence and damp risk.

• If your project includes adjacent paving that affects surface drainage, ICPI guidance emphasizes systematic subgrade preparation and drainage control in interlocking pavement construction—these principles matter because poor drainage next to walls increases splash-back and damp load on masonry.

8. Incorrect damp-proofing and “bridged” DPC

Why it matters: Rising damp and salt movement are among the most dispute-prone defects because they damage finishes and can drive efflorescence/staining. SANS 10400-K requires a damp-proof course at the top of a ground-bearing slab and not less than 150 mm above adjacent finished ground level; AfriSam’s rising damp note quotes these provisions and illustrates common bridging failures.

Prevention steps

• Install DPC at top of slab level and keep it ≥150 mm above external finished ground.

• Do not bridge the DPC with external plaster/render; where plaster is required, detailing must prevent bypassing.

• Ensure external ground levels and paving fall away from walls to reduce water loading.

9. Improper handling and transport on site

Why it matters: Chipped edges and cracked units are often created between delivery-offload and the point of laying. Mishandling drives waste, weakens aesthetics, and can become a dispute if the load wasn’t inspected on receipt.

Prevention steps

• Move packs with equipment/methods that reduce damage; BIA workmanship guidance explicitly calls for moving site-packaged units in ways that limit damage.

• Store pallets stable, off ground, and covered before they are broken open.

• Keep facings protected from mortar droppings/paint splashes throughout the contract (a common contractual requirement).