Question 1

1. What are trench blocks?

Accepted Answer

Trench blocks are large-format concrete or aircrete blocks used to form foundation walls below ground level. They’re designed to carry structural loads and transfer them into the footing and ground below. The wider size of trench blocks compared to regular concrete blocks allows them to support full wall widths, including cavity construction, reducing the number of courses required compared to standard blocks.

Question 2

2. What are trench blocks used for in construction?

Accepted Answer

In construction, trench blocks are primarily used to create stable, reinforced, and insulated foundation bases. They’re designed to fill and support foundation trenches, providing a solid, level footing that distributes structural loads evenly across the ground. Common applications include supporting load-bearing walls, retaining walls, and underground structures in both residential and commercial projects. Their versatility and strength make them a popular choice for foundational work in diverse construction environments, from simple extensions to complex infrastructure projects.

Question 3

3. How much are trench blocks?

Accepted Answer

In the UK, trench block prices typically vary depending on size, strength, and material. Lightweight aircrete trench blocks often start from around £6–£12 per block, with higher-strength or wider units costing more. Overall cost depends on quantity, delivery, and project specification, but fewer blocks are needed compared to standard masonry, which can offset material costs.

Question 4

4. How many trench blocks are there in a pack?

Accepted Answer

Pack sizes vary by manufacturer and block size, but trench blocks are usually supplied in smaller quantities than standard blocks due to their weight and size. Typical packs may contain around 40–72 blocks per pallet, though this varies widely, and single blocks are often also available.

Question 5

5. How many trench blocks fit in a square metre?

Accepted Answer

Trench block coverage depends on the block size and how it’s laid. As a guide, around 20–30 trench blocks per m² is typical. Wider blocks laid flat will reduce the number required, while narrower or differently oriented blocks will increase it.

Trench blocks

Thermalite 300mm Trenchblock T&G 3.6N

Hi-strength Thermalite Trench Blocks 7.3N 300mm