How to Measure Your Loft for Boarding and Calculate Materials

One of the most common questions from homeowners planning to board their loft is: "How much material do I actually need?" Getting this right before you order saves you money, reduces waste, and means you are not making unnecessary trips to collect extra boards. This guide walks you through exactly how to measure your loft space and calculate the precise number of boards, stilts, and fixings required. Step 1: Safety First Before you enter your loft with a tape measure, take a moment to prepare. Always use a proper loft ladder and wear knee pads if you plan to spend time moving around. Only ever step on the ceiling joists — never between them — as the plasterboard ceiling below will not support your weight [1]. A head torch or a temporary light source is essential for accurate measuring in a dark loft space. Step 2: Sketch Your Loft Layout Take a pencil and paper into the loft and sketch a rough floor plan of the space. Note the position of the loft hatch, any water tanks, pipework, electrical cables, and the point where the roof slope meets the floor (the "knee wall"). You only need to board the area where you can comfortably stand or crouch — typically the central ridge area of the loft. Mark on your sketch which areas you intend to board. Most homeowners board a central rectangular zone, leaving the eaves clear for ventilation. Step 3: Measure the Area to Be Boarded Using a tape measure, record the length and width of the area you plan to board. For a simple rectangular zone, the calculation is straightforward: Area (m²) = Length (m) × Width (m) For example, if your boarding zone is 4 metres long and 3 metres wide, your total area is 12m². If the space is irregular (for example, an L-shape), break it into smaller rectangles, calculate each one separately, and add the totals together. Step 4: Calculate the Number of Boards Our OSB Loft Boards measure 1220mm × 300mm, which is 1.22m × 0.3m = 0.366m² per board. To find the number of boards needed: Number of boards = Total Area (m²) ÷ 0.366 Using our 12m² example: 12 ÷ 0.366 = approximately 33 boards. We recommend adding 10% to your total to account for cuts and wastage. So for 12m², order approximately 36–37 boards. Step 5: Calculate the Number of Loft Stilts Loft stilts are installed at regular intervals to support the boards above the insulation. Our Loft Stilts DIY Pack is designed to support boards at the correct spacing. As a general rule, stilts should be placed at every joist crossing point beneath the board joints, and at regular intervals along the length of each board. For our 1220 × 300mm boards, you will typically need stilts at: Each end of the board (at the 0mm and 1220mm positions) The midpoint of the board (at approximately 610mm) Along the 300mm width at each joist In practice, for a 12m² area, plan for approximately 4–5 stilts per square metre, giving you around 50–60 stilts for our example area. The exact number will depend on your joist spacing. Step 6: Calculate Fixings Each board will need to be secured to the stilts using screws. Our 4.0 × 30mm Screws are the ideal size for fixing OSB boards to loft stilts. Plan for approximately 6–8 screws per board (two per stilt fixing point). For 36 boards, you will need approximately 216–288 screws. A pack of 200 screws will cover most standard loft boarding projects. Quick Reference Calculator Loft AreaOSB Boards (inc. 10% waste)Approx. StiltsApprox. Screws 6m²1825–30120–150 10m²3040–50200–250 15m²4560–75300–375 20m²6080–100400–500 Don't Forget Lighting Once your loft is boarded, you will want to be able to see what you are storing. The LOFT LIGHT — Magnetic LED Loft Lamp requires no wiring and attaches magnetically, making it the perfect finishing touch for a newly boarded loft. Ready to order your materials? Browse our full range of Loft Boarding Products at The DIYer. References [1] Health and Safety Executive. "Working in roof spaces." hse.gov.uk.