You’re preparing to roof your house, and your contractor has asked you to purchase mabati.
But how many sheets should you order?
Twenty? Forty? Sixty?
The answer depends on your roof’s dimensions, design and the type of roofing sheets you intend to use.
You cannot accurately calculate the number of mabati sheets from the number of bedrooms alone.
A three-bedroom bungalow with a simple gable roof may require a very different quantity from a three-bedroom house with a complicated hip roof.
Fortunately, there is a straightforward way to estimate the number of sheets needed for a simple roof.
This guide explains the calculation and the information you should obtain before purchasing materials.
What determines the number of mabati sheets?
Four important factors influence your roofing sheet requirements.
1. Roof dimensions
You need to know the dimensions of the roof surfaces being covered.
The building’s floor area is not the same as its roofing area.
Roof overhangs, slopes and architectural features can increase the area requiring coverage.
2. Roof design
A simple gable roof has two main sloping surfaces.
A hip roof has additional sloping faces.
More complicated roofs may include valleys, dormers and intersections.
These features can increase cutting requirements and material wastage.
3. Roofing sheet profile
Different mabati profiles have different effective coverage widths.
For example, Mabati Rolling Mills publishes an effective cover width of 1,015 mm for its MaxCover roofing sheets.
Its Covermax product has a narrower effective cover width of 780 mm.
That difference affects how many sheets are required to cover the same roof.
4. Sheet length
Roofing sheets are available in different lengths, and some manufacturers offer custom-cut options.
The required length depends on the distance from the ridge toward the eaves, including the relevant design allowances.
Your roofing contractor should confirm the correct lengths before ordering.
What is effective cover width?
Effective cover width is one of the most important measurements in roofing calculations.
A roofing sheet has an overall physical width.
However, when sheets are installed side by side, part of each sheet may overlap the adjacent sheet.
The width that actually contributes to covering the roof is therefore smaller than the sheet’s overall width.
This is called the effective cover width.
For example, a manufacturer might specify a sheet with an effective cover width of 1.015 metres.
That means each installed sheet contributes approximately 1.015 metres of coverage across the roof.
You should use the manufacturer’s effective cover width rather than assuming every sheet covers exactly one metre.
Formula for calculating mabati sheets
For a simple rectangular roof slope, the basic formula is:
Number of sheets = Roof width ÷ Effective sheet cover width
Round the result upward to the next whole sheet.
You then repeat the calculation for each roof surface.
This calculation assumes that each sheet runs continuously from the ridge toward the eaves.
More complicated arrangements may require additional calculations.
Example: Calculating mabati for a simple gable roof
Imagine you’re building a bungalow with a straightforward gable roof.
For this hypothetical example, assume the roof has the following dimensions:
| Measurement | Value |
|---|---|
| Roof width along the ridge | 12 metres |
| Number of roof slopes | 2 |
| Required sheet length | 4 metres |
| Roofing profile | MaxCover |
| Effective cover width | 1.015 metres |
The 1.015-metre effective cover width is a published specification for Mabati Rolling Mills’ MaxCover roofing profile.
The other dimensions are hypothetical and are used to demonstrate the calculation.
Step 1: Calculate sheets per roof slope
Divide the roof width by the effective cover width.
12 ÷ 1.015 = 11.82
Because you cannot order 0.82 of a full-width sheet as a standard complete sheet, round upward.
You need approximately:
12 sheets per slope.
Step 2: Calculate the total number of sheets
The roof has two identical slopes.
12 × 2 = 24
You therefore need approximately:
24 sheets.
Step 3: Calculate the total linear metres
Assume each sheet needs to be 4 metres long.
24 × 4 = 96
Your preliminary order would contain:
96 linear metres of roofing sheets.
This is an illustrative quantity calculation, not a final materials schedule.
It assumes the roof dimensions, sheet orientation and required lengths have already been correctly established.
Your contractor should confirm the dimensions, detailing and any additional allowances before you order.
Why sheet profile makes a difference
Let’s compare two roofing profiles using the same hypothetical 12-metre roof width.
Mabati Rolling Mills publishes the following effective cover widths:
| Roofing profile | Effective cover width |
|---|---|
| MaxCover | 1.015 metres |
| Covermax | 0.780 metres |
Using MaxCover:
12 ÷ 1.015 = 11.82
Rounded upward, that’s 12 sheets per slope.
Using Covermax:
12 ÷ 0.780 = 15.38
Rounded upward, that’s 16 sheets per slope.
For two identical roof slopes, the preliminary quantities become:
| Profile | Sheets per slope | Total sheets |
|---|---|---|
| MaxCover | 12 | 24 |
| Covermax | 16 | 32 |
The wider effective coverage of MaxCover means fewer sheets are required in this example.
However, fewer sheets do not automatically mean a lower material cost.
Different profiles may have different prices, gauges, finishes and installation requirements.
You need to compare the total cost of achieving the required roof coverage.
How much will the mabati cost?
Once you’ve calculated the quantity, you can estimate the roofing sheet expenditure.
If your supplier charges per linear metre, use:
Sheet material cost = Total linear metres × Supplier’s price per linear metre
For example, the hypothetical MaxCover roof above requires approximately 96 linear metres.
You would multiply 96 by the supplier’s confirmed price for the exact profile, gauge and finish you intend to purchase.
Avoid using a generic price for “mabati” without checking the product specifications.
Different suppliers and manufacturers may quote different rates.
Also confirm whether the quotation includes applicable taxes, delivery and other charges.
A roofing sheet price is not necessarily the complete cost of installing a roof.
What other roofing materials will you need?
Mabati sheets are only one component of the roofing system.
Depending on the design, you may also need:
Roof framing
This may include timber or steel structural members.
The sizes, spacing and connections should follow the approved structural design and relevant specifications.
Ridge caps
These cover the junction at the top of a pitched roof.
The required quantity depends on the ridge lengths and the effective coverage of the selected accessories.
Flashings
Flashings help weatherproof roof edges, intersections and penetrations.
The required types and quantities depend on the roof design.
Valley gutters
Roofs with intersecting slopes may require valleys to collect and direct rainwater.
A simple gable roof may not have any valleys.
Roofing fasteners
The number and type of fasteners depend on the roofing system, supporting structure and installation requirements.
Follow the manufacturer’s fixing instructions and the project’s technical specifications.
Fascia boards and gutters
These may be required along the roof edges.
Their quantities depend on the relevant perimeter lengths and drainage design.
Other specified components
Depending on the project, the roofing system may also require insulation, underlay, ventilation components or other accessories.
The complete material schedule should be developed from the roof drawings and specifications.
Can you calculate mabati using the floor area?
You can use floor area as a very rough starting point for understanding the scale of a building.
However, it is not sufficient for a reliable roofing material order.
Consider a 120 m² bungalow.
The roof may extend beyond the external walls because of the eaves.
Its sloping surfaces also have different dimensions from their horizontal projections.
If the roof contains multiple intersections, material cutting requirements may increase further.
Therefore, you should not simply divide 120 m² by the area of one mabati sheet and assume the answer is correct.
Obtain the actual roof geometry before preparing your final order.
Does roof pitch affect the number of sheets?
Yes.
Roof pitch describes how steeply the roof slopes.
For a roof with a fixed horizontal span, a steeper pitch increases the sloping distance from the ridge to the eaves.
That can affect the required sheet length.
Different roofing profiles also have manufacturer-specific minimum pitch requirements.
For example, Mabati Rolling Mills publishes minimum pitch guidance for its roofing products.
Do not assume that a profile suitable for one roof design is appropriate for every roof.
Your architect, engineer or roofing specialist should confirm that the selected roofing system is suitable for the proposed pitch.
How do you calculate mabati for a hip roof?
A hip roof is more complicated than a simple gable roof.
Its surfaces may be triangular or trapezoidal rather than rectangular.
Sheets near the hips often require angled cuts.
That means you cannot necessarily calculate the complete order by dividing the total roof area by the nominal area of a sheet.
You need to consider how the sheets will be laid out, the lengths required and the offcuts generated.
For complicated roofs, request a roof-specific cutting and quantity schedule from your contractor or roofing supplier.
This can reduce the risk of ordering incorrect quantities.
How can you reduce roofing material wastage?
One useful approach is to plan the roofing sheet layout before ordering.
Ask your contractor to confirm the required lengths and quantities for each roof surface.
Where the manufacturer offers suitable custom-cut lengths, these may reduce unnecessary cutting on site.
However, custom cutting should follow accurate measurements.
Ordering sheets that are too short can create additional joints or require replacement materials.
Ordering excessively long sheets may increase handling difficulties and wastage.
The objective is to match the supplied material to the approved roof design.
Should you buy Gauge 26, 28 or 30 mabati?
Roofing sheets are sold in different gauges and material thicknesses.
However, gauge labels should not be the only specification you use when comparing products.
Ask suppliers to confirm the actual sheet thickness, coating specification, product warranty and relevant technical requirements.
The appropriate roofing product depends on factors including the building design, support spacing, exposure conditions and manufacturer’s specifications.
Your contractor or designer should confirm which products are suitable for the project.
Avoid substituting a different roofing sheet solely because it is cheaper.
Questions to ask before purchasing mabati
Before paying a supplier, establish:
- The exact roofing profile.
- The specified material thickness.
- The coating and finish.
- The effective cover width.
- The required sheet lengths.
- The number of sheets of each length.
- The required roofing accessories.
- The applicable installation requirements.
- Delivery charges and arrangements.
- Product warranty terms.
Request a written quotation that identifies the products clearly.
You should also verify the supplier’s details and confirm the order before making payment.
Frequently asked questions
How many mabati sheets do I need for a three-bedroom house?
There is no fixed number. The quantity depends on the roof’s dimensions, design and selected roofing profile. Use the roof drawings and manufacturer’s effective coverage specifications to calculate the requirement.
How many metres does one mabati sheet cover?
A sheet’s effective cover width depends on its profile. For example, Mabati Rolling Mills publishes effective cover widths of 1.015 metres for MaxCover and 0.780 metres for Covermax. Sheet length is a separate measurement.
How many mabati sheets cover a 12-metre-wide roof?
Using a profile with an effective cover width of 1.015 metres, approximately 12 sheets are required across one simple rectangular roof slope. The total depends on the number of roof surfaces and their dimensions.
Is it cheaper to buy longer mabati sheets?
Not necessarily. The total cost depends on the supplier’s pricing, required lengths, installation arrangement and wastage. Compare complete material quotations rather than assuming longer sheets are always more economical.
Can I calculate roofing materials without architectural drawings?
You can prepare a preliminary estimate using measured dimensions. However, final quantities should be confirmed against the actual roof design before purchasing materials.
Final thoughts
Calculating mabati requirements is more straightforward when you have accurate roof dimensions and the manufacturer’s effective coverage specifications.
For a simple roof, dividing the width of each roof surface by the effective cover width provides a useful starting point.
However, roof complexity, sheet lengths, accessories and cutting requirements all affect the final order.
Before purchasing materials, ask your contractor or roofing supplier to confirm the complete roofing schedule.
And remember that roofing is only one component of your construction budget. Read our roofing-cost guide and construction cost per square metre guide to plan the wider budget.
Ready to price your mabati order?
Share your roof dimensions or drawings, preferred profile and gauge, required sheet lengths and delivery location. If you are unsure of quantities, ask for help working them out before ordering.
Request mabati supplier quotations or quantity help.
Compare the complete order, including ridge caps, flashings, fasteners, delivery and unloading. Final quantities should be confirmed against your roof design.