1. My terrace

Draw your terrace or choose a starting shape.

Starting template

…

2. My setup

Choose your terrace type, installation and materials.

Terrace type

Installation system

Materials and settings

Quantities update with your dimensions. Prefilled values are editable examples: check the manufacturers’ instructions.

Your boards

Board length (m)

Board width (mm)

Your structure

Joist length (m)

Maximum joist spacing (cm)

Maximum pedestal spacing (cm)

Joists are generated perpendicular to the boards here. Check the selected system requirements.

Layout and allowance

Selected allowance (%)

Layout direction (°)

Advanced settings

Gap between boards (mm)

3. My result

Preview your terrace and see the quantities you need.

Preview

Show layout

BoardsJoistsPedestals

Preparing the 3D view…

Layout preview20 m² · 18 m

This geometric preview is not an optimised layout and does not certify the structure.

What you need

Quantities rounded to the lengths and pack sizes entered, including your allowance.

Boards
to buy
62 boards
Need before allowance
135 m
Requirement including allowance (+10 %)
148.5 m
Purchased quantity
148.8 m
Packaging surplus
0.3 m
Pack size
2.4 m
Quantity priced
21.576 m²
Boarding price per m² (€/m²)
Material totalPrice not provided
Joists
to buy
21 joists
Need before allowance
56 m
Requirement including allowance (+10 %)
61.6 m
Purchased quantity
63 m
Packaging surplus
1.4 m
Pack size
3 m
Price per joist (€)
Material totalPrice not provided
Pedestals
to buy
126 pedestals
Units per pack (u)
theoretical
126 units
Purchased quantity
126 units
Packaging surplus
0 units
Price per pedestal pack (€)
Enter the number of units per pack to calculate the price.
Material totalPrice not provided
Fixings
to buy
4 boxes
Units per pack (u)
theoretical
756 units
Purchased quantity
800 units
Packaging surplus
44 units
Fixings box price (€)
Material totalPrice not provided

The allowance applies to boards, joists, tiles, adhesive and grout. Pedestals and fixings follow the supports and intersections in the plan. Add shop prices to estimate the budget. Quantities remain available without prices.

4. My project

Save your project and prepare the next steps.

Estimated budget

Estimate labour

Select to add a labour estimate.

Material cost: Not provided

Incomplete budget: some prices or pack sizes still need to be entered.

Excluding tools

Tools needed

Optional

Prepare your work and estimate the cost of tools you still need.

Save the shape, materials and prices to return to them later on this device.

Project name

Your projects are stored on this device.

My projects

Continue my project

Your terrace shape and dimensions will be reused automatically.

Prepare the base

Calculate excavationCalculate the volume of soil to remove.Calculate geotextileEstimate the rolls required for this area.Calculate gravelEstimate layer volume and weight.

Choose only the steps your project needs. An existing base may not require all this preparation.

Method and sources

Surplus is the difference after rounding to pack sizes. It is not an optimised cutting plan.

Selected allowance : 10 %

Rounded to whole pieces before buying

What if…?

Try a variation based on your current values. The shape stays unchanged. Reset to return to your starting values.

More help

Understand my result

How many boards and joists will you need?

Board width and the gap determine the rows. Their direction changes the lengths clipped to the outline. The tool adds these lengths, applies your allowance and divides by board length to estimate whole boards to buy.

Why pedestal count is not just a number per m²

For decking, pedestals sit on each actual joist segment. Changing joist spacing recalculates joist positions and their pedestals together. Changing only the maximum pedestal spacing leaves the joists in place.

For a straight 4 m segment with an illustrative maximum spacing of 0.60 m and a support at each end, you need 8 supports. The 7 intervals are about 0.57 m long. This explains the count; the permitted spacing comes from the manufacturer.

Supports on one segment = round up(length ÷ maximum spacing) + 1

Schematic decking on pedestals: joists run across the boards and pedestals sit on the joists. The configurator calculates your actual layout.

Turn a price per m² into a project budget

Board cost uses the area of whole boards purchased. Joists are priced per piece; pedestals and fixings follow their pack sizes. Complete missing prices before treating the budget as complete.

Then compare ground preparation, delivery, edging and labour. Use “Continue my project” in the result to reuse the zone for excavation, geotextile or gravel. Depths and products remain specific to each step.

Tips for your terrace

Board direction and structure

Joists are the supporting members under the boards. In the configuration calculated here, they run perpendicular to the boards. Joist spacing is measured between their centre lines. Reducing it adds support lines.

Check before buying

Treating the terrace area as the exact area to buy: allowance and packs can increase it.
Using one pedestal-per-m² rule for all shapes and systems.
Adding supplies a second time when they are already included in the result.
Mistaking a layout preview for a validated cutting plan.

Frequently asked questions

Does every 20 m² terrace need the same board quantity?

No. Width, gaps, direction, shape, available lengths and allowance all affect the quantity. Compare alternatives using the same zone dimensions.

Can I calculate a terrace without pedestals?

Yes. Decking without pedestals includes boards, joists and fixings. Bonded tiles use tiles, adhesive and grout. Check that your actual base suits the chosen system.

What joist spacing should I choose?

Use the maximum spacing specified for your boards and supporting structure. Product, thickness and layout affect it. The tool’s example values must be adapted.

Will the shape carry over to the rest of the job?

Yes. “Continue my project” links below the result pass the zone to the next calculators. Save in My projects to return to the shape and settings later on this device.

Method and sources

The plan is your shared starting point. Boards or tiles determine which materials are counted. Filters change only what you see: hiding pedestals does not remove them from the shopping list.

The plan uses your dimensions in metres and mathematically clips each line to the outline. It supports quantity estimates and visualisation, but does not certify the structure or edge cuts.

Displayed spacings are editable examples. Trex and Millboard publish product-specific values and require users to follow the relevant manufacturer guide. Millboard

Adding lengths does not create an optimised cutting plan. An offcut may be unusable and a joint may need a specific support. Check available lengths and joint requirements before ordering.

Which materials does each terrace need?

Choose the finish and its support first. A terrace without pedestals is a valid option. These are the items covered by the configurator; ground preparation is estimated separately.

Estimated supplies for each configuration
Your choice	Items calculated
Boards on pedestals	Boards, joists, pedestals, fixings
Boards without pedestals	Boards, joists, fixings
Pavers on pedestals	Pavers and pedestals
Bonded tiles	Tiles, adhesive and grout when consumption is supplied

Trex’s guide illustrates why spacing, direction and joints must be checked for the chosen product. It is not a universal specification. Trex — Deck joists

Deck and patio planner: layout, materials and cost