Why is cinder block the best choice for a garage?

Building a garage from cinder blocks remains one of the most popular solutions among car owners. This material combines strength, affordable price and ease of installation, which makes it ideal for self-construction. Unlike bricks, cinder blocks are larger in size, which means they can be laid faster - this reduces construction time by 30-40%. At the same time, a garage made of cinder blocks can withstand loads no worse than a brick one, if you correctly calculate the thickness of the walls and reinforcement.

But the main question that worries everyone before starting work: How many cinder blocks do you need for an 8x4 garage? The answer depends on several factors: ceiling height, wall thickness (half a block or a block), the presence of additional structures (basement, inspection pit) and even on strength grades block. In this article we will analyze all the nuances of the calculation, provide ready-made tables for typical projects and tell you how to avoid mistakes when purchasing materials.

It is important to note that cinder blocks come in different sizes. Standard size - 390×190×188 mm, but there are also half-blocks on sale (390×120×188 mm), and reinforced options with increased density. If you're planning on insulating your garage, it might be worth considering hollow blocks - they are lighter and retain heat better, but require additional waterproofing.

Initial data for calculation: what do you need to know before purchasing?

Before counting the number of cinder blocks, collect initial data about the future garage. Without this information, any calculation will be approximate, and an error of even 10-15 blocks can lead to unnecessary waste or, conversely, a shortage of material in the midst of construction.

Here key parameters, which will affect the final figure:

  • 📏 Garage dimensions: the standard 8x4 meters implies a length of 8 m and a width of 4 m, but check the project - sometimes the dimensions are indicated along the outer or inner perimeter.
  • 🏗️ Wall height: the optimal height for a garage is 2.5–3 meters. If you plan to store things on mezzanines, take the upper level.
  • 🧱 Wall thickness: half a block (190 mm) or into a block (390 mm). For an unheated garage, semi-block masonry is sufficient, but for regions with frosts below -20°C it is better to choose a block thickness.
  • 🔧 Type of masonry: with or without dressing. Ligation (shifting blocks in rows) increases strength, but requires more material for cutting.
  • 🚪 Additional openings: gates, windows, ventilation holes. Each opening reduces the number of blocks, but adds complexity to the calculations.

Don't forget about masonry joint! The thickness of the mortar between blocks is usually 10–15 mm. This means that for each meter of masonry it will take 5-7% more blocks than with a “dry” calculation. Also add reserve 10% for fighting and pruning - this is standard practice among builders.

📊 What wall thickness are you planning for the garage?
Half block (190 mm)
In block (390 mm)
I haven't decided yet
Another option

Formula for calculating cinder blocks for an 8×4 garage

To calculate the number of cinder blocks, we use a simple geometric formula:



Number of blocks = (Wall perimeter × Wall height) / (Block length × Block height) × Masonry coefficient

Let's look at it using the example of a garage. 8x4 m with wall height 2.5 m and half-block masonry (190 mm):

  1. Wall perimeter: (8 + 4) × 2 = 24 m (if the garage is rectangular without additional projections).
  2. Wall area: 24 m × 2.5 m = 60 m².
  3. Area of one block (in masonry): 0.39 m × 0.188 m = 0.0733 m².
  4. Number of blocks excluding seams: 60 / 0.0733 ≈ 819 pcs..
  5. Adjustment for seams and stock: 819 × 1.15 (15% for seams and fraying) ≈ 942 pcs.

For laying in a block (390 mm) the quantity will decrease approximately by half, but will increase foundation load. Also, don’t forget to subtract the area of the door (standard garage doors take up ~5–6 m²). In our example, this will reduce the final figure by ~70–80 blocks.

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If the garage is adjacent to a house or other structure, subtract the length of the common wall from the perimeter. For example, for an 8x4 garage adjacent to the house along a 4-meter wall, the perimeter will not be 24 m, but 20 m.

Ready-made tables: how many cinder blocks are needed for typical projects

To simplify the task, we have prepared tables with calculations for the most common garage options 8x4 m. The data is given taking into account:

  • 🧱 Masonry seam 12 mm.
  • 🚪 Standard gate 2.5×2.2 m (area ~5.5 m²).
  • ➕ Stock 10% for fighting and pruning.
Wall thickness Garage height Number of cinder blocks (pcs.) Approximate weight of blocks (t)
Half block (190 mm) 2.5 m 850–900 12.5–13.2
Half block (190 mm) 3.0 m 1020–1080 15.0–15.8
In block (390 mm) 2.5 m 420–450 12.3–13.2
In block (390 mm) 3.0 m 500–540 14.7–15.8

Important: the weight of the blocks is indicated for standard cinder blocks with a density of 1400–1600 kg/m³. If you use light blocks (for example, expanded clay concrete), the weight will decrease by 20–30%.

For garages with inspection hole or basement add to the calculation:

  • 🕳️ Pit walls: ~150–200 blocks (depending on depth).
  • 🚗 Floor reinforcement: if the pit is located under the car, a reinforced screed will be required, which will increase the load on the foundation.
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For garages in regions with high humidity (for example, the Leningrad region), choose cinder blocks with hydrophobic additives or plan additional waterproofing of the walls.

Common mistakes when calculating cinder blocks

Even experienced builders sometimes make mistakes in calculations, which leads to downtime on site or overpayments. Here top 5 mistakesthings to avoid:

  1. Ignoring the masonry seam. Many people consider blocks to be “dry”, forgetting that the solution occupies up to 15% of the volume of the masonry. For example, for an 8x4 garage this is an error of 100-150 blocks.
  2. Unaccounted base height. If the foundation rises 30–50 cm above ground level, this is an additional row of blocks around the entire perimeter.
  3. Forgotten openings. Windows, vents or additional doors reduce the number of blocks, but they are often not subtracted from the total area.
  4. Invalid stock. A 5% margin is not enough - when cutting blocks for corners and openings, the margin can reach 15%. On the other hand, 20% of the reserve is too much if you do not plan to complete the garage.
  5. Block size errors. Not all cinder blocks are the same! Check with the seller exact dimensions - a difference of even 1 cm will give an error of 50-100 blocks for a large garage.
⚠️ Attention: If you order cinder blocks from different suppliers, check that the batches were from the same mixture. Blocks from different manufacturers may differ in strength and size, which will complicate the laying.

One more nuance - masonry reinforcement. For garages with a height of 3 meters or more or in earthquake-prone regions, it is necessary to reinforce every 3-4 rows of masonry with a metal mesh. This does not affect the number of blocks, but adds reinforcement costs and increases construction time.

Check the exact dimensions of the block with the seller|Calculate the area of all openings (gates, windows)|Add 10–15% margin for breaking and trimming|Check quality certificates (strength grade not lower than M75)|Check delivery conditions (some suppliers charge a fee for lifting to the floor)-->

How to save on cinder blocks without losing quality?

Building a garage is an expensive undertaking, but you can save money by using cinder blocks without sacrificing strength. Here are some proven methods:

  • 💰 Buy blocks in bulk. Many factories give a discount of 5% when ordering over 1000 pieces. Make an agreement with neighbors or friends who also need blocks.
  • 🏗️ Choose semi-block masonry. Thickness 190 mm sufficient for an unheated garage in most regions of Russia. This reduces material consumption by almost 2 times compared to laying in a block.
  • ♻️ Use used blocks. At construction sites, leftover cinder blocks are often sold at a price 30–50% below the market price. The main thing is to check them for cracks and strength.
  • 📦 Order pick-up delivery. If you have a truck, you will save 10–20% of the cost of the blocks (delivery usually costs 500–1500 rubles per trip).

Also note seasonal discounts. In spring and autumn, the demand for building materials falls, and many suppliers hold sales. For example, in March-April, prices for cinder blocks may be 10-15% lower than in June-July.

⚠️ Attention: Don't skimp on strength grade blocks! For a garage, the minimum brand is - M75. Blocks M50 and below are only suitable for internal partitions and will not withstand the load from the roof or snow.

If you are planning garage insulation, consider the option with well masonry: two rows of blocks with a gap, which is then filled with insulation (for example, polystyrene foam). This will increase the consumption of blocks by 20–30%, but will reduce heating costs in the future.

Step-by-step instructions: how to calculate cinder blocks yourself?

In order not to rely on ready-made tables, we will learn how to calculate the number of blocks ourselves. Let's take the garage as an example. 8x4 m with wall height 2.8 m, half-block masonry and gates 2.5×2.2 m.

  1. Step 1. Calculate the perimeter of the walls: 
    (8 + 4) × 2 = 24 m (perimeter)
  2. Step 2. Find the area of the walls: 
    24 m × 2.8 m = 67.2 m²
  3. Step 3: Subtract the gate area: 
    2.5 × 2.2 = 5.5 m²

    67.2 m² – 5.5 m² = 61.7 m² (masonry area)
  4. Step 4. Calculate the number of blocks per 1 m²: 
    1 m² / (0.39 m × 0.188 m) ≈ 13.6 blocks

    Taking into account the seam 12 mm real quantity - ~12.5 blocks/m².

  5. Step 5. Total quantity: 
    61.7 m² × 12.5 = 771 blocks

    771 × 1.1 (10% margin) ≈ 850 blocks

To check use alternative method — calculation by rows:

  • Wall height: 2.8 m.
  • Block height including seam: 0.188 + 0.012 = 0.2 m.
  • Number of rows: 2.8 / 0.2 = 14 rows.
  • Number of blocks in a row (perimeter 24 m, block length 0.39 m): 24 / 0.39 ≈ 62 blocks/row.
  • Total: 14 × 62 = 868 blocks (excluding gates and reserves).

The difference between the methods (~20 blocks) is due to rounding and masonry features. For accuracy, use both methods and take the average.

How to take into account windows and ventilation?

If the garage has a window (for example, 1x1 m), subtract its area from the total:

1 m² / 0.0733 m² (block area) ≈ 14 blocks.

For ventilation holes (for example, 2 pieces of 0.2x0.2 m each):

0.04 m² × 2 = 0.08 m² → ~1 block.

Total savings: ~15 blocks.

FAQ: Answers to frequently asked questions about cinder blocks for the garage

Is it possible to build a two-story garage out of cinder blocks?

Technically possible, but you will need:

  • Use brand blocks M100–M125 (not lower!).
  • Strengthen the foundation (strip or slab, at least 1 m deep).
  • Reinforce the masonry through each row with metal mesh or reinforcement.
  • Take into account the additional load from the floor (usually reinforced concrete slabs are used).

For the second floor, it is better to choose lighter materials (for example, frame panels) to reduce the load on the walls.

How many cinder blocks do you need for an 8x4 garage with basement?

For the basement add:

  • Basement walls: ~150–200 blocks (depending on depth).
  • Basement slab: If using cinder block beams, you will need ~100-150 more blocks.

Approximate calculation for a basement 2 m deep:



Perimeter: 24 m


Wall area: 24 × 2 = 48 m²


Blocks: 48 × 12.5 ≈ 600 pcs.

Total for garage + basement: ~1400–1500 blocks (half a block).

What kind of foundation do you need for an 8x4 cinder block garage?

Optimal options:

  • Strip foundation (depth 50–70 cm, width 30–40 cm). Suitable for most soils, except heaving ones.
  • Slab foundation (thickness 15–20 cm). More expensive, but reliable on soft soils.
  • Columnar foundation (pillars every 1.5–2 m). Cheaper, but requires a rigid grillage.

For cinder block walls doesn't fit pile foundation - it does not ensure uniform load distribution.

How to insulate a garage made of cinder blocks?

Effective ways:

  • External insulation: polystyrene foam (5–10 cm) + plaster. Cheap, but requires protection from rodents.
  • Internal insulation: mineral wool + plasterboard. Retains usable area, but “eats” 10–15 cm of space.
  • Well masonry: two rows of blocks with insulation inside. Expensive, but reliable.

Mandatory for heated garages vapor barrier (for example, foil foam) to avoid condensation.

Is it possible to build a garage out of cinder blocks in winter?

It is possible, but with reservations:

  • Use winter masonry mortar with antifreeze additives.
  • Store blocks under a shed or cover them with a tarp - wet blocks lose strength.
  • At temperatures below -10°C, it is better to stop laying - the solution will not gain strength.

The optimal time for construction is from April to October.