Concrete Blocks or Laterite Blocks? Choosing Walling in The Gambia
Both have been used here for decades and both work. The choice depends on the building, not on which is "better" — and in either case the quality of the individual block matters more than the material.
The two options
Most walling in The Gambia is built from one of two things: hollow concrete blocks cast in a yard from cement, sand and aggregate, or laterite blocks cut from the ground. Both are long-established, both perform well when made and used properly, and the argument about which is superior is mostly an argument about which building you are talking about.
How they compare
Swipe horizontally to compare all columns.
| Hollow concrete block | Cut laterite block | |
|---|---|---|
| Made from | Cement, sand and aggregate, cast and cured | Cut from laterite deposits, hardens on exposure |
| Consistency | High — controlled moulds and mix | Variable — depends on the deposit |
| Thermal mass | Moderate; 9-inch noticeably better than 6-inch | High — interiors stay cooler |
| Suits framed multi-storey | Yes — the standard choice | Less commonly used above ground floor |
| Cement required | Higher | Lower — mainly for mortar and render |
| Speed of building | Faster, uniform coursing | Slower where units vary |
| Typical use today | Most modern construction | Boundary walls, single-storey, exposed feature walls |
For a reinforced concrete framed building of two storeys or more — which covers most modern construction here — hollow concrete blocks are the practical choice. The frame carries the load and the blockwork infills it, so consistency and speed matter more than the block’s own compressive strength.
For single-storey buildings, boundary walls and situations where keeping interiors cool without air conditioning matters, laterite is worth serious consideration. Its thermal mass is a genuine advantage in this climate, and it requires less cement.
The thing that matters more than the choice
A well-made concrete block outperforms a poor laterite block, and a good laterite block outperforms a badly made concrete block. In practice the quality of the individual unit matters far more than which of the two materials you picked.
For concrete blocks, quality comes down to two things: the mix and the curing.
Mix
Cement is the expensive ingredient, so the standing temptation is to stretch it with more sand. An over-sanded block looks identical to a properly proportioned one when it leaves the yard, and behaves nothing like it in a wall. You cannot see this by inspection.
Curing
Concrete gains strength through hydration, which needs moisture and time. Blocks should be kept damp and left for at least seven days before being laid, and they continue gaining strength well beyond that. Blocks sold two or three days after casting have not developed their strength and never fully will — allowing them to dry out early causes permanent loss.
How to check blocks before you accept a delivery
- Ask the casting date and whether they were kept damp through curing.
- Look at the edges and corners. Heavy chipping and crumbling at the arris indicates weak or green blocks.
- Check dimensional consistency across the load. Varying heights mean more mortar, more render and slower laying.
- Look at the colour. Very pale, sandy-looking blocks can indicate a low cement content.
- Knock two together. A sound block rings; a weak one thuds dully.
- Watch how they survive offloading. Blocks that break on handling will not improve in the wall.
None of these is a laboratory test, and none is conclusive alone. Together they will tell you quickly whether a load is worth accepting.
Choosing between 6-inch and 9-inch
The number is the wall thickness. Nine-inch blocks go in external and load-bearing walls: the extra thickness carries load and gives better thermal mass, so interiors stay noticeably cooler through the afternoon. Six-inch blocks are typically used for internal partitions and non-load-bearing walls, where the saving in material and floor space is worth having.
Using 6-inch throughout to save money is a false economy on external walls in this climate. The saving is real and modest; the additional cooling load is permanent.
Related questions
Are laterite blocks strong enough for a house?
For single-storey construction and boundary walls, good laterite blocks are entirely adequate and have been used here for a very long time. For multi-storey work the load is carried by a reinforced concrete frame in any case, and hollow concrete blocks are the usual infill because of their consistency and laying speed.
How many blocks do I need per square metre of wall?
It depends on the block dimensions your supplier produces, so calculate it from their actual sizes rather than a standard figure. Measure the wall area, subtract openings, divide by the face area of one block, and add around five per cent for cuts and breakages.
Can I mix concrete and laterite blocks in one building?
Yes, and it is sometimes sensible — laterite for a boundary wall or a feature elevation, concrete blocks for the framed structure. What matters is that the mortar, coursing and any render system suit each material rather than being applied uniformly across both.
Why do blocks crumble in the wall?
Almost always because they were laid before curing was complete, or because the mix was over-sanded. Occasionally it is sulphate attack from unsuitable sand or persistent damp from a failed damp-proof course. The first two causes are far more common and both are decided at the block yard, not on site.