Roofing is often the biggest single material cost after the structure itself, and the number people budget is almost always too low because it only counts the sheets. Here is a simple way to go from a roof plan to a sheet count, and what else to put on the list.
Step 1: Measure the roof, not the floor
A house that is 10 m long on the ground has a longer roof, because the slope adds length and the eaves overhang the walls. Measure each roof slope separately: its length along the ridge, and its length from ridge to eaves following the slope, including the overhang. Then add the slopes together.
Step 2: Choose the profile, then check its cover width
Every profile has an effective cover width, the width one sheet actually covers once its overlap with the next sheet is taken out. It is always less than the sheet's full width, and it differs between profiles, so confirm the figure for your chosen profile with our sales team before you count.
Step 3: Count sheets across, then choose a length
Divide the length of the slope along the ridge by the effective cover width, and round up. That gives the number of sheets in one row. Then pick a sheet length that runs from ridge to eaves. Standard lengths are 2 m, 2.5 m and 3 m, and we cut to any length you need, so you can order exactly the run you measured and avoid joins.
Step 4: Allow for waste
Add roughly 10% for cuts, overlaps and mistakes. Hips, valleys and dormers eat more sheet than a plain gable, so keep the allowance at the top of that range if your roof has them.
A worked example
Take a simple gable roof 10 m long, with two slopes that each measure 3.5 m from ridge to eaves, including the overhang. Suppose the profile you choose has an effective cover width of 0.8 m (this figure is for illustration only). Each row needs 10 รท 0.8 = 12.5, which rounds up to 13 sheets, so the two slopes need 26 sheets of 3.5 m.
That is 91 m of sheeting. At our current listed rate for Colour 11/3 Profile of per metre at Gauge 30, the sheets alone come to about . This is an indicative figure; your gauge, colour and length will change the final quote.
What else belongs in the budget
- Ridge caps and flashings, which seal the ridge, the wall junctions and the eaves.
- Fasteners and washers, bought in the right type and quantity for the roof area.
- The roof structure: timber or steel purlins and rafters, sized for the gauge and span you chose.
- Gutters and downpipes, especially if you plan to harvest rainwater.
- Delivery, which varies with distance and order size.
- Labour, which changes with roof complexity and profile.
Get it checked before you order
Send us your roof dimensions and location on WhatsApp and we'll work out the sheet count and a quote with you. It's quicker than doing it alone, and it catches the expensive mistakes before they reach the site.