Planning the construction of a garage always begins with the question of the budget, and the lion's part of it is the purchase of wall materials. An error in calculations can lead to the fact that you will have to purchase missing items of goods, paying for delivery again, or, conversely, take out leftovers that have nowhere to put them. To avoid such situations, you need to clearly understand how to correctly calculate the amount of work and take into account all the nuances of masonry.
In this article we will analyze the methodology for calculating the number of blocks for standard and non-standard garage sizes. We will take into account the thickness of the walls, the presence of gates, windows and armored belts so that you can make the most accurate estimate. A competent approach to numbers at the project stage is the first step to saving resources.
Choosing a block type and its effect on the quantity
Before moving on to mathematics, you need to decide on the material itself. Expanded clay concrete and aerated concrete the blocks have different dimensions, which directly affects the final number of pieces per cubic meter. The standard size of a wall block is often 20x20x40 cm, but there are also variations with a height of 30 cm or a length of 60 cm.
If you are using gas block brand D500 or D600, it is important to consider that it requires more precise masonry geometry, often using glue, which reduces the thickness of the seam. Expanded clay blocks, on the contrary, are often placed on a cement-sand mortar, the seams of which can “eat up” the useful volume and visually increase the consumption of material if work is not done carefully.
It is also worth paying attention to the hollowness of the product. Solid elements are stronger, but heavier, while hollow elements retain heat better. For a garage, where the load-bearing capacity of the walls for installing doors and shelves is important, compromise options with partial filling are often chosen.
- 🧱 Dimensions: The 200x200x400 mm standard is the most common and convenient for calculations.
- 🏗️ Density: For an unheated garage, the density D500-D700 is sufficient; for a heated garage, D700-D900 is better.
- ❄️ Thermal conductivity: Aerated concrete is warmer than expanded clay concrete, which allows you to make walls thinner with the same efficiency.
It is important to understand that the size declared by the manufacturer may differ from the actual size by 5-10 mm. This is a manufacturing tolerance, which in large volumes can result in an error of several rows. Therefore, when purchasing material, always clarify whether the geometric dimensions are being calculated or based on actual ones.
Basic formula for calculating the number of blocks
There are two main ways to calculate how many pieces of material will be needed: through the area of the walls or through their volume. The first method is easier to understand, the second is more accurate for ordering cubic capacity. Let's look at the area method, since it is the most obvious for self-construction.
First, the perimeter of the future structure is calculated. For a garage measuring 6 by 4 meters, the perimeter will be (6 + 4) * 2 = 20 meters. This figure is then multiplied by the planned height of the walls, for example, 2.5 meters. We get a total wall area of 50 square meters. From this figure it is necessary to subtract the area of gates, doors and windows.
⚠️ Attention: When calculating the area of the walls, do not forget that corner blocks are counted twice if you simply multiply the perimeter by the height. It is more accurate to calculate the area of each wall separately, subtracting half the thickness of the block in the corners, but for an approximate estimate, an error of 2-3% is acceptable.
After obtaining the net area of the walls, it is divided by the area of the side surface of one block. For a standard 20x40 cm, this area is 0.08 sq.m. Thus, 12.5 blocks are needed per 1 sq.m of wall. Multiplying the net wall area by 12.5 will give you the base number of pieces.
Why 12.5 blocks per square?
If we divide 1 meter by the length of the block (0.4 m), we get 2.5 pieces in a row. If we divide 1 meter by the height of the block (0.2 m), we get 5 rows. 2.5 times 5 equals 12.5. This is true for masonry in one block (20 cm thick).
Don't forget about the reserve. Fight during transportation and cutting when adjusting rows is inevitable. Experienced builders recommend adding 5 to 10% to the calculated amount for losses. For brittle aerated concrete, it is better to keep this percentage closer to the upper limit.
Consideration of wall thickness and type of masonry
Wall thickness is a critical parameter that determines the stability of the garage and its thermal insulation properties. For a one-story building made of blocks, masonry of one block (20 cm) or one and a half blocks (30 cm) is most often used. Half-block (10 cm) masonry for a garage is permissible only as partitions or temporary structures.
If you choose a 20 cm masonry, then the calculation is based on the length and height of the block. If a more permanent wall of 30 or 40 cm is planned, the amount of material increases proportionally. In this case, it is more convenient to count not in pieces, but in cubic meters, converting them into pieces already in the warehouse.
| Wall thickness | Consumption of blocks (pcs/sq.m) | Recommended Application |
|---|---|---|
| 10 cm (0.5 block) | 12.5 pcs (flat) | Internal partitions, outbuildings |
| 20 cm (1 block) | 12.5 pcs (edge) | Garages for cars, sheds |
| 30 cm (1.5 blocks) | 18-19 pcs | Garages in windy regions, under roof cover |
| 40 cm (2 blocks) | 25 pcs | Northern regions, heated boxes |
When choosing a thickness of 30 cm, they often use a bunch of blocks of different sizes or put a 20 cm block and add 10 cm, which complicates the calculations. In this case, it is better to purchase material with a margin of 10-15%, since the trimming will be significant.
It is also important to consider reinforcing belt. If, according to the project, a concrete belt is planned to be poured on top of the walls under the Mauerlat for the roof, then the height of the masonry blocks is reduced by the height of this belt (usually 15-20 cm). This can save you several rows of material.
☑️ Check before ordering blocks
Calculation for garages of different sizes
Let's put the theory into practice for popular sizes. The most common option is a 6 by 4 meter garage. With a wall height of 2.5 meters and masonry in one block (20 cm), the wall area will be: (6+6+4+4) 2.5 = 50 sq.m. Subtract the gate (2.5 2.2 = 5.5 sq.m) and window (1 * 1 = 1 sq.m). Net area: 43.5 sq.m. Multiply by 12.5 and get 544 blocks. Plus 5% stock - a total of about 570 pieces.
For a more compact version of 3 by 6 meters (often attached to a house), the logic is the same. Perimeter: (3+3+6+6) = 18 meters. Wall area (at a height of 2.5 m): 45 sq.m. If one wall of 6 meters is common with the house and is not being built, then we count only three walls: (3+3+6) * 2.5 = 30 sq.m. Minus openings, plus margin. The numbers will be significantly smaller, but the principle remains the same.
For large boxes for two cars, for example 6 by 8 meters, the wall area increases proportionally. Here it is critically important to correctly calculate the need for pallets. Blocks are often sold in packs of 1.5 or 1.8 cubic meters. Rounding up to a whole pallet may give a small surplus, which, however, will be useful for the construction of pillars or repairs in the future.
Order blocks in whole pallets - this is often cheaper per unit and ensures that all the material is from the same batch, which is important for consistent color and density.
Don't forget about plinth. If the garage does not stand on a slab foundation flush with the ground, but has a raised base made of brick or concrete, the height of the block part of the walls is reduced. This must be subtracted from the total height before calculating the number of rows.
Nuances: openings, lintels and pediments
Windows and gates are holes in the budget if you count them as walls, and savings if you deduct them correctly. Large swing or sectional gates take up a significant area. A standard gate 2.5x2.2 meters is almost 70 blocks that you don’t need to buy. However, if the gate is installed on brick pillars, then the blocks for the pillars must be counted separately.
Above the openings must be installed reinforced concrete lintels or U-blocks with reinforcement are used. The height of the lintel is usually 15-20 cm. This means that above each window or gate another row of blocks falls, which is also not purchased, but requires the cost of concrete or ready-made lintels.
⚠️ Attention: Never rest the jumpers simply on a thin layer of mortar. The minimum depth of support of the lintel on the wall should be 20-25 cm on each side, otherwise the structure may crack under the weight of the masonry above.
If the garage is planned with gable roof, it is necessary to calculate the material for the gables (triangular ends of the walls). The gable area is calculated as half the product of the width of the garage and the height of the ridge. These blocks often come with trimming, so the percentage of waste here increases to 10-15%.
Final estimate and purchasing advice
The final stage is to summarize all the numbers into a single table. Do not try to count “by eye” or by the number of pallets from your neighbor. Each garage is unique in its openings and height. Use the resulting formula: (Perimeter Height - Prems) 12.5 + 5%.
When ordering material, pay attention to the delivery conditions. Heavy blocks require a manipulator for unloading. If you cannot accept 10-15 tons of material at once, consider delivering in parts, although this may be more expensive. Blocks should be stored on a flat surface, protected from moisture, especially if it is aerated concrete.
- 🚛 Logistics: Check the access roads for long trucks with a manipulator in advance.
- 💧 Storage: The gas block is afraid of water, cover the pallets with film, but leave vents at the bottom.
- 🧱 Grade: Place blocks with broken corners on backfill or unimportant areas where chips are not visible.
Correct calculation means not only saving money, but also eliminating downtime. When the material runs out in the middle of the day, construction stops. It’s better to have a few whole blocks left than to have a dozen missing.
Always round the total number of blocks up to the whole pallet or pallet - this will optimize delivery and unit price.
Do seams need to be taken into account in the calculations?
In the simplified calculation (12.5 blocks per sq.m.), the thickness of the seam is already taken into account indirectly, since the actual size of the block with the seam gives exactly this figure. If the seams are very thick (more than 10 mm), slightly fewer blocks will be needed, but the strength of the wall will decrease. To accurately calculate the volume in cubes, the seams can be ignored, since they occupy a small proportion (about 3-4%).
What is cheaper: gas block or expanded clay block?
The price per cube may be comparable, but expanded clay block is often stronger and does not require mandatory reinforcement of each row, unlike aerated concrete. However, the gas block is easier to saw and lay, which saves time and glue. The final turnkey cost is often the same.
How many blocks are in one pallet?
A standard Euro pallet holds about 1.5 - 1.8 cubic meters of blocks. With a block size of 20x20x40 cm, there are 62.5 pieces in one cube. This means that there will be approximately 90-110 blocks on the pallet, depending on the height of the stack and the loading capacity of the pallet.