A sturdy and well-built subframe is essential for the longevity and stability of your decking. Whether you’re planning to install composite decking or any other type of decking material, the quality of the subframe is crucial.

In this guide, we’ll cover the dos and don’ts of subframe installation for decking, drawing from industry best practices and guidelines.

Don’ts of Subframe Installation

Skimp on Materials

Avoid using substandard materials or cutting corners to save costs. Invest in high-quality pressure-treated timber and corrosion-resistant fixings to ensure the longevity and stability of your deck.

Neglect Ground Preparation

Skipping proper ground preparation before subframe installation can lead to expensive issues. Avoid uneven settling, poor drainage, and weed growth, compromising the integrity of the subframe and decking by with careful preparation. Take the time to level the ground and install adequate ground protection before laying the subframe.

Overlook Proper Spacing

Improper spacing of joists can result in uneven decking, sagging, and structural instability. Follow the manufacturer’s guidelines and local building codes to determine the correct spacing and support requirements for your decking project.

Forget to Seal Exposed Ends

Exposed ends of pressure-treated timber are susceptible to moisture absorption and rot. Seal the cut ends with a suitable wood preservative or end sealer to protect them from water damage and prolong the lifespan of the subframe.

Dos of Subframe Installation

Start with a Level Surface

Before laying the subframe, ensure that the ground is level and well-compacted to provide a stable base for the deck. Use a spirit level and a string line to check for any unevenness and make adjustments as needed.

Install Ground Protection

Place a layer of landscape fabric or weed membrane over the ground surface before subframe installation to prevent weed growth and moisture build-up underneath the deck. This helps to improve drainage and airflow, reducing the risk of rot and decay in the timber subframe.

ground membrane artificial grass decking subframe installation

Choose Pressure-Treated Timber

Opt for pressure-treated timber for the subframe, as it is resistant to rot, decay, and insect damage, ensuring long-lasting durability. Use timber that is suitable for outdoor use and meets the relevant industry standards for structural integrity.

Use Proper Spacing and Support

Space the joists at regular intervals to provide adequate support for the decking boards, typically between 16 to 24 inches apart, depending on the decking material and load requirements. Install support beams perpendicular to the joists to distribute the weight evenly and prevent sagging or warping over time.

Use Stainless Steel or Galvanised Fixings

Use stainless steel or galvanised fixings, screws, and brackets to secure the subframe components together. These corrosion-resistant materials ensure the structural integrity of the subframe and prevent rust and degradation over time.

Now you know how how to prepare the foundations for decking subframe installation, shop our stunning range of decking on our website.

Taking the time to properly prepare the ground, use quality materials, and adhere to spacing and support guidelines will result in a durable and long-lasting deck that you can enjoy for years to come.


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When installing composite decking, always revert to the fitting instructions for the best possible finish.

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