How to calculate the area of the deck, if your size doesn’t match our calculator:

Multiply the length by the width to get the total area.

Determine the number of deck boards:

Divide the total area by the area covered by one deck board (including the 5mm gap).
Round up to the nearest whole number since you can’t have a fraction of a deck board.
Calculate the number of carcassing:

Determine the number of joists required based on the size and spacing.
Adjust the number based on the length and width of the deck.
Estimate the quantity of screws:

Determine the number of screws based on the number of deck boards and any additional structural elements.

Find the area of weed fabric:

Match the area of the weed fabric to the area of the deck.

Let’s perform these calculations for a sample deck size (3.6m x 3.6m):

Area of the deck:

Area = Length x Width
= 3.6m x 3.6m
= 12.96 square meters
Number of deck boards:

Area covered by one deck board = (3.6m – 0.005m) * (3.6m – 0.005m) (to account for the 5mm gap)
≈ 12.59 square meters
Number of deck boards = Total area / Area covered by one deck board
= 12.96 square meters / 12.59 square meters
≈ 1.03 (rounded up to 2 boards)
Number of carcassing:

Based on standard spacing of 500mm, you would typically need approximately 8 to 9 joists for a 3.6m span. We’ll assume 9 for this calculation.
Estimate screws:

Depending on the design, you might need around 2 screws per deck board, so for 2 boards, we’ll estimate around 4 screws.
Weed fabric:

The area of the weed fabric would match the area of the deck, which is 12.96 square meters.

When it comes to constructing a sturdy and reliable deck, choosing the right joists is crucial. Our decking calculator offers several options tailored to different project needs.

Let’s delve into what each option entails and how to make the best choice for your project.

Joist Spacing:
It’s important to note that our calculator works out the joists at 500mm centers. This spacing ensures optimal support and distribution of weight across the deck structure, enhancing its stability and longevity.

100mm Joists:
These joists are ideal if you’re not raising your deck off the ground significantly. They provide ample support and stability for your decking boards while keeping the structure close to the ground. If your deck doesn’t require extensive load-bearing capabilities or if you’re working within height constraints, 100mm joists are an excellent choice.

125mm Joists:
For projects where load-bearing capacity is a priority or if you prefer a bit more clearance from the ground, 125mm joists are the way to go. These joists offer additional strength and resilience, making them suitable for decks that will bear heavier loads or decks that need to be elevated further off the ground. Choosing 125mm joists ensures added durability and peace of mind, especially for larger or more complex decking projects.

150mm Joists for Raised Decks (not added to calculator yet):
If you require significant elevation for your deck, we recommend opting for 150mm joists. These joists provide the necessary support and stability for decks raised off the ground, ensuring structural integrity and longevity. Whether you’re building a raised platform, a multi-level deck, or simply prefer a higher clearance, 150mm joists offer the robustness needed for elevated decking projects.

Considerations for Selection:

• Load Bearing: Assess the intended use of your deck and the potential weight it will bear. If you anticipate heavy furniture, foot traffic, or other significant loads, opting for 125mm or 150mm joists is advisable.
• Height Requirements: Evaluate how high you want your deck to sit above the ground. While 100mm joists are suitable for lower elevations, 125mm and 150mm joists provide more clearance if desired.
• Personal Preference: Some individuals simply prefer the added robustness and stability that larger joists offer, regardless of specific project requirements.

Conclusion:
Whether you choose 100mm, 125mm, or 150mm joists, rest assured that each option is designed to meet your decking needs. Selecting the appropriate joist size ensures that your deck is not only functional and resilient but also tailored to your specific preferences and project requirements.

Our decking boards are supplied in lengths that are tailored to fit your project seamlessly. Each board is calculated to cover 150mm, comprising 145mm for the board itself and a 5mm gap allowance for expansion and contraction. This thoughtful design ensures not only an aesthetically pleasing appearance but also accommodates the natural movements of the wood, enhancing the longevity of your deck.

Additionally, all screws necessary for installation are included with your decking purchase, eliminating the need for separate sourcing and ensuring a hassle-free installation process.