Two block suppliers quote you for the same wall. One price is clearly lower, so the choice looks easy. But a block is only one of the things a wall is made of, and the price of the block is rarely the price of the wall. Let us follow the cost further than the invoice.
The belief
A block is a block. The cheaper one saves me money, and nobody will see the difference once it is plastered.
It is true that nobody sees a block once the wall is finished. That is exactly why its quality matters: if it is wrong, you find out later, behind the paint.
What a wall really costs
Buying blocks is the first line of a longer bill. Here is everything that sits behind the price of a finished wall:
- The blocks themselves, including the ones that arrive cracked or crumble when handled.
- The mortar that joins them. Blocks that are uneven in size need more of it to level each course.
- The mason’s time. Straight, uniform blocks go up faster than irregular ones.
- The plaster that covers the wall. A wavy wall takes a thicker coat to look flat, and every extra centimetre is more cement and sand.
- Repairs. Cracks, damp patches and crumbling corners that appear after the paint is dry.
- Strength. Whether the wall can carry what it is meant to carry, and whether it holds up to rain and ground moisture.
A cheaper block can quietly add to every item after the first. A slightly more expensive block that is straight, strong and well cured can lower several of them.
Questions to ask yourself
Before you accept the lower price, put these to the supplier, your builder, and yourself:
- Are both quotes for the same size and the same strength of block, or only the same name?
- How long were the blocks cured before delivery? Blocks that were moved or loaded too soon are weaker than they look.
- If I pick one up and knock two together, do they ring or crumble? How many break on the way from the lorry to the site?
- Are the blocks the same size, or will the mason be levelling with extra mortar and the plasterer filling gaps?
- What load does this wall carry? Is it a boundary wall, a partition, or a wall holding up a floor, and does the block suit that job?
- Who decided the block strength for this building: the supplier, the builder, or the person who designed the structure?
- If a wall cracks in two years, who will I call, and what will fixing it cost compared with what I saved?
You will not have an answer to all of them, and that is fine. The ones you cannot answer tell you where you need more information before you buy.
Comparing two quotes fairly
Try this on paper before you decide. Take one wall of your building, say ten square metres, and write down what it would cost with each block. Include the blocks, the mortar, the labour and the plaster. Add a sensible allowance for breakage. Then compare the totals, not the prices per block.
Sometimes the cheaper block still wins, and that is a perfectly good result. What matters is that you chose it on the cost of the wall, not on the cost of the block.
One more thing before you order
Block strength, thickness and spacing are not guesses. They are set by what the structure has to carry, and they should be written on the drawings so the supplier and the builder are working from the same page. If yours are not written down, ask who decided them and on what basis.
Planning materials for a project and want to know where it is safe to save and where it is not? Tell us what you are building, and we will talk it through, whether or not you end up working with us.
