Decking Calculator

Fast, accurate and free online tarasu calculator tool running directly in your browser.

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Instructions

1

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2

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3

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                                                function runTool() {

                                                  return "Result ready in 0.1s";

                                                }

Terrace dimensions

Length (m)

Width (m)

Reserve for taunts (%)

Surface material

Slabs / stoneware rectangular tiles Decking boards composite / wood

Slab dimensions

Slab length (cm)

Slab width (cm)

Price per board (PLN)

Additional costs (optional)

Labor / m² (PLN)

Edging / meter (PLN)

Enter the dimensions of the terrace and click "Calculate terrace".

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Terrace calculator – how to calculate the necessary materials and construction costs?

Building a terrace is one of the best investments that increases the comfort of life of household members and increases the value of the property. The terrace is a natural extension of the living room, creating an ideal place to relax, meet friends and barbecue on warm days. Regardless of whether you are planning a wooden terrace (made of Siberian larch, pine or exotic wood) or a modern terrace made of composite boards (WPC), the key to success is to precisely calculate the necessary materials. Construction requires the purchase of boards, structural joists forming the grid, decking screws and leveling brackets. Our free online terrace calculator is a comprehensive cost estimation tool that calculates the need for all key materials based on the dimensions of the planned terrace.

Thanks to this, you will plan your purchases precisely, avoid wasting material on trimmings and learn the estimated cost of the investment before starting work.

Comparison of terrace materials - natural wood vs. composite (WPC)

The choice of material affects the aesthetics, durability and the need for subsequent maintenance of the terrace. The table below compares the most popular solutions:

Board material	Advantages and strengths	Disadvantages and weaknesses	Maintenance required	Estimated durability
Pine / Domestic spruce	Low purchase cost, easy availability, natural appearance.	Low hardness, susceptible to moisture, rot and pests.	Oiling at least 1-2 times a year.	5 – 10 years
Siberian larch	Average cost, high density, natural resistance to fungi thanks to a large amount of resin.	Susceptible to twisting, longitudinal cracks if not cared for.	Oiling once a year.	15 – 25 years
Exotic wood(e.g. Bangkirai, Cumaru)	Extreme hardness, beautiful grain, no knots, high resistance to weather conditions.	Very high purchase price, difficult processing (requires specialized drills).	Optional oiling (to preserve color, without oil it turns gray).	30 – 50 years
Composite board (WPC)	No knots and warping, uniform color, rot-resistant, non-slip surface.	Heats up strongly in the sun, less natural appearance ("plastic" character of weaker composites).	None (pressure washing only).	20 – 30 years

How to calculate terrace materials? Methodology and formulas

Calculation of demand is based on the dimensions of the terrace (length $L$ and width $W$) and parameters of selected materials:

Terrace area ($A$):Basis of calculation: $$A = L \times W$$
Number of deck boards:Calculated taking into account the width of the board ($w_d$) and the expansion gap ($g_s$, usually 4-6 mm for composite or wood). The effective opacity width is $w_e = w_d + g_s$. We divide the total length of the boards by the commercial length (e.g. 3 m or 4 m) and add 10% allowance for cutting.
Number of joists for the terrace:The joists are placed perpendicular to the direction of the boards with a spacing (axial) of every 40-50 cm (the thinner the board, the denser the joist spacing). The number of rows of joists is calculated by dividing the length of the terrace by the spacing and adding one starting row.
Number of deck screws:Each board must be screwed to the joist at two points at each intersection. The average consumption is assumed to be **35 - 40 screws for each 1 m²** of the terrace surface.

Practical assembly tips

When building a terrace, remember a few critical rules of construction craftsmanship:

Maintain the slope:The terrace structure must have a slope of 1-2% (i.e. 1-2 cm of slope for each meter of length) directed outwards from the building, which allows free drainage of rainwater and prevents rotting of the structure.
Insulation of joists from the ground:Wooden or composite joists cannot lie directly on the ground or concrete. Use rubber pads (EPDM) or adjustable supports to cut off capillary rising damp.
Use stainless steel screws (C2 / A2):Ordinary black or galvanized screws will quickly corrode under the influence of moisture and tannins contained in the wood, which will lead to cracking and loosening of the boards.

Frequently asked questions (FAQ)

What joist spacing is optimal for terrace boards?

For standard boards with a thickness of 24-28 mm, the axial spacing of the joists should be a maximum of 40-45 cm. In the case of thinner boards or composites with a chamber profile, the spacing should be narrowed to 30-35 cm. Too large a joist spacing will cause the boards to bend when walked on, which in the long run will damage the screw connections.

Why is an expansion gap between boards mandatory?

Wood is a hygroscopic material that "works" - it swells under the influence of moisture in winter and shrinks under the influence of sunlight in summer. WPC composites, in turn, expand under the influence of temperature. No gaps (expansion joints) with a width of min. 4-6 mm would cause the boards to press against each other, which would lead to their bulging, cracking and breaking of the fastening screws.

Can a wooden terrace be placed directly on the ground?

Absolutely not. Without a stable, permeable base (e.g. a layer of compacted gravel/aggregate) and insulation, wood lying close to the ground will rot within 2-3 years. The terrace should be placed on concrete foundation blocks, formwork pipes poured in the ground or on screwed steel piles.

How many screws do I need to attach one board?

Use exactly 2 screws at each intersection of the board and the joist. The screws are installed at a distance of approximately 1.5-2 cm from the side edge of the board. Screwing it with one screw in the middle of the board is a mistake because it does not prevent the so-called boating of the board (curling its edge upwards).

What is the difference between Spax-D screws and regular wood screws?

Professional terrace screws (e.g. Spax-D type) are made of stainless steel, have a special tightening thread (which permanently connects the board to the joist, eliminating squeaking), milled ribs under the head (thanks to which the head is aesthetically flush with the wood surface) and a drilling tip that prevents the board from cracking during screwing.