A standard 3 bedroom bungalow of about 150 square metres needs roughly 3,400 to 3,600 nine inch blocks, including the foundation blockwork and a wastage allowance. Below is the full working, step by step, so you can adjust every assumption to your own plan instead of trusting a number from the internet. Order the right quantity once and you avoid the two expensive failures: a second haulage trip for 300 blocks, or 500 blocks weathering in your compound for a year.
The short answer
| Scope | Blocks |
|---|---|
| Superstructure walls only (DPC to roof) | about 2,570 |
| Foundation blockwork (footing to DPC) | about 675 |
| Subtotal before wastage | about 3,245 |
| Final order with 5 to 10 percent wastage | 3,400 to 3,600 |
Order 3,500 and you will be right for most 150 square metre bungalows. Now here is how that number is built, so you can rebuild it for your own drawing.
The five numbers the calculation needs
- Total length of walls in metres, external and internal
- Wall height in metres, floor to roof beam
- Total area of doors and windows to subtract
- Blocks per square metre of wall
- A wastage percentage
Get those five right and the arithmetic is trivial. Get any of them wrong and no formula saves you.
Step 1: Blocks per square metre, and why it is 10
A 9 inch block has a face of 450 x 225mm, which is 0.10125 square metres. One divided by 0.10125 gives 9.88 blocks per square metre with no mortar.
Add a 10mm mortar joint and each block plus its joint occupies 460 x 235mm, which is 0.1081 square metres, giving 9.25 blocks per square metre.
Nigerian practice uses 10 blocks per square metre, and that is the right figure to use. The small margin over the theoretical 9.25 quietly absorbs cutting at corners and openings, which is exactly where blocks get broken. Use 10 and stop worrying about it.
Note this important point: a 6 inch block has the same 450 x 225mm face. Only the width changes. So the block count in this article is identical whether you build in 6 inch or 9 inch. Only the price per block changes.
Step 2: Measure your wall length
For a 150 square metre bungalow, assume a footprint of roughly 15m x 10m.
External walls: 2 x (15 + 10) = 50 linear metres
Internal walls: a 3 bedroom bungalow with a living room, dining area, kitchen, three bedrooms, two or three bathrooms and a corridor typically has internal walls close to the external perimeter in total length. Measuring off a standard plan gives about 45 linear metres.
Total wall length: 95 linear metres.
Measure your own plan properly rather than accepting these. Walk the drawing wall by wall and write each length down. Internal wall length is where estimates go wrong, because it is easy to forget bathroom returns, wardrobe walls and the corridor.
Step 3: Multiply by wall height
Standard Nigerian residential wall height is 3m from finished floor level to the underside of the roof beam. Some builds go to 3.3m for a cooler room.
95 metres x 3 metres = 285 square metres of gross wall area.
If your ceiling height is 3.3m instead, multiply by 3.3 and everything downstream scales with it.
Step 4: Subtract doors and windows
This is the step most people skip, and skipping it adds several hundred unnecessary blocks to your order.
| Opening | Size | Number | Area |
|---|---|---|---|
| Main entrance door | 1.2 x 2.1 m | 1 | 2.52 sqm |
| Rear or kitchen door | 0.9 x 2.1 m | 1 | 1.89 sqm |
| Internal doors | 0.9 x 2.1 m | 7 | 13.23 sqm |
| Bedroom windows | 1.2 x 1.2 m | 3 | 4.32 sqm |
| Living room window | 1.8 x 1.2 m | 1 | 2.16 sqm |
| Dining window | 1.2 x 1.2 m | 1 | 1.44 sqm |
| Kitchen window | 1.2 x 1.2 m | 1 | 1.44 sqm |
| Toilet windows | 0.6 x 0.6 m | 3 | 1.08 sqm |
| Total | 18 openings | 28.08 sqm |
That is about 10 percent of the gross wall area, which is typical for a residential building. A house with large sliding windows can reach 15 percent, and a heavily glazed design more than that.
Net wall area: 285 minus 28.08 = 256.92 square metres. Call it 257.
Step 5: Convert area to blocks
257 square metres x 10 blocks per square metre = 2,570 blocks for the superstructure.
Step 6: Add the foundation blockwork
The number almost every online estimate leaves out. Below damp proof course you still lay blocks, usually solid 9 inch blocks, from the top of the footing up to DPC level.
Not every internal wall carries down to foundation, so assume the 50m external perimeter plus about 25m of internal load bearing walls, giving 75 linear metres. Four courses at 225mm each gives a height of 0.9m.
75m x 0.9m = 67.5 square metres x 10 = 675 blocks.
On a sloping site, or where you are filling to raise floor level, this figure climbs quickly. Count your courses on site rather than assuming four.
Step 7: Add wastage
Blocks break. They break being loaded, being offloaded, being carried up a scaffold, and being cut at corners and openings. They also break because someone stacked them badly.
Use 5 percent if your access is good, your ground is firm and your labour is careful. Use 10 percent for a tight site, a long carry from the delivery point, or a rainy season build where blocks are being moved through mud.
The full working in one table
| Step | Working | Result |
|---|---|---|
| External wall length (15m x 10m footprint) | 2 x (15 + 10) | 50 m |
| Internal wall length | measured off plan | 45 m |
| Total wall length | 50 + 45 | 95 m |
| Gross wall area | 95 x 3 | 285 sqm |
| Less openings | from openings table | 28.08 sqm |
| Net wall area | 285 – 28.08 | 256.92 sqm |
| Superstructure blocks | 256.92 x 10 | 2,569 |
| Substructure blockwork | 75 x 0.9 x 10 | 675 |
| Subtotal | 2,569 + 675 | 3,244 |
| With 5 percent wastage | 3,244 x 1.05 | 3,406 |
| With 10 percent wastage | 3,244 x 1.10 | 3,569 |
Final answer: 3,400 to 3,600 blocks. Order 3,500 for a typical 150 square metre 3 bedroom bungalow.
What that costs, and what else you need to order
At an indicative planning range of ₦950 to ₦1,350 per 9 inch block, 3,500 blocks comes to roughly ₦3.3 million to ₦4.7 million. Block prices move with cement, diesel, location and order size, so treat that as a budget band and get a dated quote before you commit.
Two things to order alongside the blocks:
- Mortar cement. Masons in Lagos generally budget one bag of cement for every 50 to 60 blocks laid. A 3,500 block job therefore needs somewhere around 60 to 70 bags for laying alone, before rendering.
- Sharp sand. Order in full trips rather than part loads. Part loads carry the same haulage cost spread over less material, which is money burnt on diesel.
How to adapt this to your own plan
| If your plan differs | What to change |
|---|---|
| Larger or smaller floor area | Recalculate the perimeter, and scale internal wall length with it |
| Wall height of 3.3m instead of 3m | Multiply gross wall area by 3.3, everything else follows |
| More or larger windows | Increase the openings deduction, which reduces the block count |
| Deep foundation or sloping site | Count actual courses below DPC and recalculate step 6 |
| Boundary or fence wall | Calculate it separately, it is often 800 to 1,500 blocks on its own |
| Duplex rather than bungalow | Repeat the whole superstructure calculation per floor |
The single biggest source of error is internal wall length. If you take one thing from this article, take a measured internal wall figure off your actual drawing rather than a rule of thumb.
Should you split the order between 6 inch and 9 inch?
Yes, and it saves real money. Your 2,570 superstructure blocks split roughly into 1,170 external and load bearing (9 inch) and 1,400 internal partitions (6 inch). At a difference of about ₦250 per block, switching those 1,400 internal blocks to 6 inch saves in the region of ₦350,000, with no reduction in structural performance because those walls carry nothing but themselves.
Keep every external wall, load bearing wall and all substructure blockwork in 9 inch. That is not the place to economise.
What this means for your project
You now have a number you can defend, and more usefully a method you can rerun when the drawing changes. Ordering 3,500 blocks in one scheduled delivery rather than guessing at 3,000 and topping up later saves you a repeat haulage charge, gets you volume pricing, and keeps your masons working instead of standing idle waiting on a truck. And because you have deducted openings properly, you are not paying to store 400 blocks you will never lay.
Get your block count quoted by Naydo Keystone
Send Naydo Keystone Ventures your floor plan or your wall measurements and we will work out the block count for your 3 bedroom bungalow, split it correctly between 6 inch and 9 inch, and quote it as one scheduled delivery. We manufacture 4, 6 and 9 inch hollow blocks, solid blocks, cement bricks and face bricks in Satellite Town, Lagos. Every batch is tested before it leaves the factory, and delivery is free within our Lagos service area. Request your free quote today.
Related
Compare every block size on our concrete blocks in Lagos page, budget with the 9 inch block price guide, and choose widths with 6 inch vs 9 inch blocks. For the frame and slabs, see iron rods and reinforcement steel.
