If you're planning to make the most of your loft space, one popular solution is installing loft boards to create a storage platform. But there's a common question that comes up during the planning stages: Can you put loft boards directly on joists? In this comprehensive guide, we’ll explore whether this approach works or if there’s a better alternative—using Loft Legs—and why they might be your best bet.
Can I Install Loft Boards Directly on Joists??
In many modern properties, joist heights typically range between 75mm and 100mm, though older properties may have varying or even irregular heights. According to current government guidelines, loft insulation should be at least 270mm thick, usually in the form of mineral wool or quilt insulation, which is the most common method.
When you place loft boards directly on joists, you risk compressing or even having to remove some of the insulation. This can drastically reduce the thermal efficiency of your insulation.
In fact, studies show that compressing 270mm of insulation down to just 100mm can reduce its effectiveness by over 50%. For newer homes with up to 400mm of insulation, this issue is even more pronounced.
Insulation materials, like quilt insulation, work by trapping air within their fibres, which helps to slow down the transfer of heat. This trapped air is what gives insulation its thermal resistance (also known as R-value).
When the insulation is compressed, the fibres are squashed together, reducing the air pockets that are essential for its insulating properties. As a result, the material becomes denser and less effective at keeping heat in (or out), which significantly reduces its ability to maintain the desired temperature in your home.
To avoid these problems, let's look into other ways to install loft boards that will preserve your insulation and improve energy efficiency.
What Are Loft Joists and Loft Boards?
Before diving into the installation options, it’s important to understand the basic components involved:
Loft Joists: These horizontal beams, typically spaced between 400mm and 600mm apart, provide structural support to the roof and ceiling. Joists are usually made of timber.
Loft Boards: Loft boards are flat panels, typically made from chipboard or OSB, that create a solid surface for storage. They come in thicknesses of 18mm to 22mm, with thicker boards being more durable and capable of supporting more weight..
Are Your Joists Strong Enough?
Before you install loft boards, you need to ensure your joists are strong enough to handle the weight of both the storage items and anyone moving around the loft. In new builds, trusses are designed* to support 25kg/m² plus the weight of a person walking in the loft. Older properties may require a professional survey to determine their load capacity.
*Extract from EN1991-1-1 (Superseding British Standard BS 6399-1:1996)
Section 6.3.4.2 Values of Actions
The following loads are appropriate for the design of frames and covering of access hatches (other than glazing), supports of ceilings and similar structures:
a) without access: no imposed load: orb) with access: 0.25KN/m² uniformly distributed over the whole area and a concentrated load of 0.9KN so placed as to produce the maximum effect in the supporting members
How to Prevent Insulation Compression
There are two main solutions for installing loft boards while preserving the insulation:
1. Timber Sub Frame Method
The traditional approach involves cross-battening the joists with timber to create a raised platform for the boards. However, this method is expensive and adds considerable weight to the structure. For homes with deep insulation (over 270mm), this solution may not be suitable due to the increased weight and cost.
2. Loft Legs: The Ideal Solution
A more efficient and cost-effective option is to use Loft Legs—specially designed supports that raise loft boards above insulation, ensuring that the insulation remains effective.
What Are Loft Legs?
Loft Legs are made from ultra-strong, recycled plastic, and they’re designed to create a gap between your loft boards and joists. This gap prevents compression of insulation, preserving the thermal efficiency. Loft Legs are lightweight, easy to install, and can accommodate pipes and cables without causing thermal bridging. These supports simply screw into the joists, and the loft boards are then secured on top.
Why Choose Loft Legs?
Better Insulation Performance: Loft Legs raise the boards above the insulation, preventing it from becoming compressed and maintaining its efficiency.
Easy Installation: Loft Legs are simple to install and offer a stable base for the boards. You don’t need to worry about excessive weight or creating thermal bridges.
Durable and Lightweight: The strong, recycled plastic construction ensures that the system can support heavy storage while remaining lightweight and easy to handle.
For homes with deeper insulation, Loft Leg XL offers an even taller solution, suitable for homes with up to 400mm of insulation.
Step-by-Step Guide to Installing Loft Boards Using Loft Legs
Here’s how to install your loft boards using Loft Legs:
Tools and Materials Needed:
Loft Legs or Loft Leg XLs (according to your insulation depth)
Loft boards (18mm-22mm thick)
Electric Screwdriver
Stanley Knife
Screws (30mm long, 4mm diameter general purpose screws)
Measuring tape
Saw (for cutting boards)
Installation Steps:
Prepare the Loft Area: Clear any debris and ensure the joists are in good condition. If necessary inspect for any rot, damp, damage or signs of stress.
Measure the Joist Spacing: Measure the distance between joists to determine how far apart the Loft Legs will be placed. This will help to calculate how many Loft Legs you will need for your project.
Plan the Loft Leg Grid: Plan where each Loft Leg will be secured. This will be determined by the distance between your joists and the size of loft boards you are using. For example, the grid will consist of a Loft Leg on each joist in one direction, then along the joist there will be a Loft Leg at the outer edges of the platform and Loft Legs at every point where the loft boards meet. The most efficient scenario would be a 600mm x 600mm grid if this size of board can be transported and the loft hatch is large enough. The least efficient scenario would be 400mm x 320mm if the joists are spaced at 400mm and 320mm x 1200mm loft boards are being used. More information on how many legs and how to plan the Loft Leg grid can be found here.
Install the Loft Legs: Screw the Loft Legs into the joists, spacing them no more than 600mm apart and based on the instructions in stage 3. Make sure they’re secure. Roll the top layer of insulation out over and around the Loft Legs. Where the insulation meets a Loft Leg create a small slit in the quilt with a Stanley knife and gently push down around the leg.
Position the Loft Boards: Place the loft boards on top of the Loft Legs, making sure they’re fully supported.
Secure the Loft Boards: Use screws to secure the boards to the top of the Loft Legs.
Check Stability: Test the boards for stability to ensure there’s no movement in the raised platform.
Start Storing: Once everything is installed, you can begin storing your items. Be sure to distribute weight evenly across the boards to prevent excess loading of individual attic joists or trusses. Loft Leg recommend limiting storage to no more than 25Kg/m2.
A step by step movie detailing all the necessary stages can be found here.
Note: Before loft boarding it is a good idea to upgrade the lighting to make sure you are safe while working and to create a bright and inviting space once the loft boarding is complete. The Loft Light and Loft Bulb by Loft Leg have been designed specifically for lofts. The Loft Light is a bright battery powered LED that can create lighting without the need for electrical wiring. While the Loft Bulb is a main powered 4000 Lumen bulb that fits into a standard B12 Bayonet lamp fitting. The Loft Bulb has three ultra-bright LED panels that are adjustable and can direct the light into the darkest corners of any loft.
Loft Legs vs. Boarding Directly on Joists
While it’s technically possible to install loft boards directly on joists, Loft Legs offer a superior solution in terms of insulation preservation, ease of installation, and long-term stability. By using Loft Legs, you’ll create a secure, functional storage space without compromising on energy efficiency.
Ready to Start?
Now that you know the answer to "Can you put loft boards on joists?", it’s clear that using Loft Legs is the better option for most homes. They’re an easy, cost-effective way to ensure your loft space is safe, functional, and energy-efficient.
If you’re ready to begin or need help with the process, don’t hesitate to get in touch! We’re happy to assist with any questions or guide you through the installation.