Measuring An Industrial Roof For Coating

A Best Practice Guide

Best Practice for Measuring an Industrial Roof for Coating Works

This guide explains how to measure an industrial metal roof for coating works, allowing contractors to estimate roof areas, laps, gutters and details when preparing refurbishment quotations.

When pricing or estimating the cost of an industrial roof coating project, the quality of the measurements matters.

A roof area taken from above is a useful starting point, but on its own it is rarely enough. To prepare a realistic quotation, it is also important to understand the condition of the roof, for example, the extent of corrosion, whether mid-laps require sealing, whether any previous treatments are present, and whether the roof has actually been inspected.

This guide explains how to measure an industrial metal roof for coating works when preparing a contractor quotation, including roof area correction, corrosion measurement and mid-lap sealing requirements.

It is useful for professional specifiers and roof coating contractors preparing tender documentation and specifications for budget costing and material pricing estimation.

Key Information Required for a Roof Coating Quotation

Overall roof area in square metres
Profile and pitch correction (typically up to 20%)
Total length and width of edge corrosion
Total length and width of mid-lap corrosion
Whether mid-laps require sealing
Sealing method (HP Butyl Tape or sealant)
Whether existing cut edge treatments are present
Whether measurements are from Google Earth or physical inspection

Accurate roof measurements allow coating contractors to prepare realistic quotations and help ensure the correct refurbishment strategy is selected for the roof.

Considerations When Measuring Industrial Roofs

It’s always best for contractors to take their own measurements directly on the roof, since this is the most accurate method. This might not always be feasible for a number of reasons, so other alternatives are the use of scaled drawings if available or by using online tools such as Google Earth.

However the area is measured, always add c20% to account for the roof pitch and corrugations, because failing to do so could have a dramatic effect on the amount and cost of materials and labour needed to complete the job.

Measuring For Cut Edge Corrosion

Whether a full roof coating or a stand-alone cut edge corrosion treatment is being priced, the cut edges at both mid-laps and end-laps should be measured properly.

This time there are three variables:

The length of the cut edges at both mid-laps and end-laps
The width of the cut edges at both mid-laps and end-laps
Whether the mid-lap joints are to be sealed – and by what method

The width refers to the toal band width of the treatment that is necessary, so typically, measurements are taken from the cut edge to the highest point of corrosion, plus 25mm.

Where a mid-lap treatment requires the joint to be sealed and both the top and bottom sheets treating, the measurement should be from the highest point of corrosion on the top sheet to the lowest point of corrosion on the bottom sheet, plus 50mm.

Mid-laps and end-laps should be measured separately, since end-laps will never require sealing and therefore, will almost certainly have a narrower band width than at the mid-lap joints.

When Mid-Lap Joints Require Sealing

Sometimes, the specification calls for sealing mid-lap joints and for this, there might be different options like sealant or butyl tape.

Check whether an existing cut edge treatment is already present

If a previous cut edge corrosion treatment has already been applied, this can affect both pricing and suitability for overcoating.

Older treatments may be:

cracked
brittle
poorly adhered
debonded
trapping moisture
masking deterioration of the sheet edge
hiding a much bigger defect

In some cases, what appears acceptable from aerial imagery may prove problematic when inspected more closely.

Record whether

no previous treatment is visible
a previous treatment is visible
it is unknown because the roof has not been inspected closely

Where an existing treatment is present, an on-site survey may be necessary before a reliable quotation or tender document can be provided.

Be clear about what cannot be confirmed remotely

Remote measurement can be useful for early budgeting, but it has limits.

Google Earth, roof plans and aerial imagery cannot always confirm:

the true severity of corrosion
whether previous treatments are sound or failing
whether roof sheets are thinning or deteriorating
whether laps are open
whether sealing is appropriate
whether local repairs may be required

Where these points cannot be confirmed, it is sensible to allow for the possibility that an on-site survey may be required before final pricing or specification is agreed.

Recap Checklist Summary

Before requesting a quotation for roof coating works or material costing, try to provide the following information.

Roof area

overall roof size in m²
include profile and pitch correction (up to 20%)

Edge corrosion

total linear metres
average band widths

Mid-lap corrosion

total linear metres
average band widths

Mid-lap sealing

whether sealing is required
length to be sealed
whether HP Butyl Tape or Sealant is proposed

Existing treatment

whether any previous cut edge corrosion treatment is already present

Inspection method

whether measurements are based on Google Earth, drawings, drone imagery or a physical inspection

Survey requirement

whether the roof can be priced reliably from the available information
or whether an on-site inspection is likely to be required.

Practical guidance

For early budget pricing, approximate measurements from online tools may sometimes be enough.

For firm quotations, particularly where corrosion is significant or previous repairs are visible, a physical inspection is often the better approach.

The aim is simple: gather enough information at the start so the quotation reflects the actual condition of the roof, not just the plan size of the building.

Accurate roof measurements allow appropriate refurbishment systems to be identified and material quantities to be estimated, enabling contractors to obtain reliable pricing for systems such as Liquasil’s metal roof coating and gutter lining solutions.