Commercial and Industrial Roof Waterproofing: A Guide for Property and Facility Managers

For a business, a body corporate or a property owner, a leaking roof is not just a maintenance item. It damages stock and equipment, stops production lines, creates slip hazards, annoys tenants and, if it is ignored, shortens the life of the whole building. At the same time, replacing a large roof is one of the biggest capital costs a property will face.

This guide is for facility managers, property managers, managing agents, trustees and business owners responsible for warehouses, factories, workshops, office parks, shopping centres and sectional title complexes. It covers why large roofs fail, the options for fixing them, how to do the work without shutting operations down, the rules around asbestos and sectional title maintenance, and how to plan roof maintenance so that leaks stop being emergencies.

In this guide

Why commercial roofs are different
Common commercial roof types and where they fail
The cost of doing nothing
Patch, restore or replace?
Waterproofing without downtime
Asbestos roofs
Sectional title complexes and body corporates
Planned roof maintenance
How a project is run, step by step
Specifying and comparing quotes
Rooftop solar and waterproofing
Budgeting for roof waterproofing
Insurance and documentation
Considerations by building type
Roof inspection checklist
Roof coatings and building heat
Common mistakes on commercial roofs
All commercial roof guides
Frequently asked questions

Why Commercial Roofs Are Different

Scale: industrial roofs often cover thousands of square metres, so a few hundred leaking fixings or laps add up quickly.
Downtime: every day a section of a building cannot be used costs money, so how the work is done matters as much as what is done.
Complexity: plant rooms, aircon units, ducts, skylights, solar arrays, box gutters and changes in level create many more details than a house roof.
Responsibility: managers answer to owners, tenants, trustees or insurers, and need a documented specification, a clear scope and a guarantee.
Safety: roof work is work at height and must be planned and carried out in line with occupational health and safety requirements.

Common Commercial Roof Types and Where They Fail

IBR and corrugated warehouse and factory roofs

The workhorse of South African industry. Failures start at perished screw washers, side and end laps, ridge caps, skylight upstands and rusted areas, especially where swarf from drilling was left on the roof. Box gutters overflow in heavy storms. See why IBR roofs leak, corrugated roofs and metal roofs.

Flat concrete roofs on offices, retail and apartments

Common on office parks, shopping centres and apartment blocks. Original bitumen membranes dry out and crack, drains block, and parapets and plant plinths leak at their junctions with the slab. See flat roof waterproofing.

Asbestos cement roofs

Still found on many older factories and outbuildings. Weathered sheeting becomes brittle and cracks, and fixings loosen. See asbestos roofs below.

Complex and mixed roofs

Many commercial buildings combine roof types, with additions built over the years, multiple levels and dozens of penetrations. See complex roof waterproofing.

Sectional title complexes

Tile and IBR roofs over townhouses, flat slabs over apartment blocks, and box gutters and parapets shared between units. Responsibility for the roof is usually the body corporate’s. See sectional title below.

The Cost of Doing Nothing

Small leaks on commercial roofs grow, and the indirect costs usually exceed the cost of the repair:

Damaged stock, raw materials, equipment and electrical systems
Stopped production or closed areas while leaks are managed
Wet floors and slip hazards for staff and customers
Corrosion of roof sheeting, purlins and fixings that turns a waterproofing job into a re-roof
Tenant complaints, lost tenants and rental disputes
Insurance complications, because many policies exclude gradual deterioration and poor maintenance

Patch, Restore or Replace?

Option	When it fits	Limitations
Spot repairs	Newer roofs with a few defined problems	On ageing roofs, the next leak is usually close behind
Restore with a liquid membrane	Structure and most sheeting or slab sound; leaks across many joints and fixings	Sheets that are rusted through must be replaced first
Partial replacement plus restoration	Most of the roof sound, some areas beyond saving	Needs a clear survey to separate the two
Full replacement	Structure failing or covering beyond repair across the roof	Highest cost and disruption

For many commercial roofs, restoring the existing roof with a seamless, fully bonded liquid membrane gives the best balance of cost, disruption and lifespan. It covers every lap, fixing and detail in one layer, adds UV protection to the sheeting underneath, and avoids the removal and disposal costs of a re-roof. For a fuller comparison, see our guide on waterproofing versus re-roofing in the guides list.

Waterproofing Without Downtime

EcoProof’s systems were chosen with commercial work in mind:

Applied from above: work happens on the roof, not inside the building.
No flames: the system needs no flames, solvents or primers, which avoids the hot work risks of torch-on systems over occupied or stocked buildings.
Fast cure: the spray grade surface cures almost instantly, so sections are protected the same day.
High coverage: spray application covers up to 800 m² a day.
Phasing: large roofs can be done section by section around shifts, deliveries, shutdowns and tenant needs.

In most cases production carries on as normal underneath. See industrial roof waterproofing.

Asbestos Roofs

Asbestos cement roofs that are structurally sound and not friable can often be encapsulated: cleaned with a filtration system and sealed under a spray-applied membrane that locks the fibres in place and protects the sheeting from further weathering. This is usually far cheaper and less disruptive than removal and disposal. Sheeting that is badly broken, crumbling or friable is not suitable for encapsulation.

In South Africa, asbestos in place is governed by the Asbestos Abatement Regulations, 2020, under the Occupational Health and Safety Act. They deal with identifying asbestos in place, keeping an inventory, and the duties of clients and registered asbestos contractors for asbestos work. If your building has asbestos, check your obligations with a registered asbestos professional before any work is planned. See asbestos roof encapsulation.

Sectional Title Complexes and Body Corporates

In most sectional title schemes the roof is common property, so its maintenance is the body corporate’s responsibility rather than the individual owner’s, even when a leak only affects one unit. Check your scheme’s rules for any exceptions.

Under the Sectional Titles Schemes Management Act and its Prescribed Management Rules, body corporates must have a written maintenance, repair and replacement plan for the common property covering at least the next ten years, setting out the major items, their condition, when work will be needed and the estimated cost, and linked to the reserve fund contributions. The roof is usually one of the largest items in that plan.

Practically, that means trustees and managing agents should:

Have the roof inspected and its condition recorded for the 10-year plan
Budget for waterproofing as a planned item rather than an emergency
Treat the whole roof or a whole block at once where possible, rather than unit by unit
Keep records of the specification, the contractor and the guarantee

EcoProof Africa regularly quotes for body corporates and managing agents and can phase work to fit the reserve fund.

Planned Roof Maintenance

The cheapest roof is one that is looked after. A simple programme:

When	What to check
Before the rainy season (late winter)	Clear gutters, box gutters and outlets; check fixings, laps, flashings and skylights; book any waterproofing
After major storms or hail	Look for damaged sheets, blocked outlets and new leaks inside
After autumn leaf fall	Clear gutters and outlets again
Whenever new equipment is installed	Have penetrations for solar, aircon or ducts sealed properly
Every two to three years	Professional inspection of the roof and the waterproofing

Keep a simple roof log with dates, findings, photos and work done. It helps with budgeting, insurance and any future guarantee claims. See also the best time to waterproof and our hail damage checklist.

How a Project Is Run, Step by Step

Survey the roof. Inspect the whole roof from above and below, record its condition, identify leak sources and any sheets or areas that must be replaced, and note access and safety requirements.
Prepare the specification and quote. Set out the areas, the repairs, the system, the coverage, the programme and the guarantee in writing so that the scope is clear to owners, trustees or tenants.
Plan around operations. Agree the phasing, working hours, access routes, safety arrangements and any areas to be kept clear underneath.
Prepare the roof. Clean the surface, treat rust, replace failed sheets and secure loose fixings so the membrane bonds to a sound substrate.
Seal the details. Treat laps, fixings, ridges, flashings, skylights, gutters and penetrations with the brush and roller grade first.
Apply the membrane. Spray the main membrane over each section to the specified thickness, completing and protecting each area as work progresses.
Inspect and hand over. Check the finished roof, provide the guarantee and documentation, and agree a maintenance schedule.

Specifying and Comparing Quotes

When comparing quotes for a large roof, make sure each one answers the same questions:

Is the roof area measured, and is the whole roof included or only parts?
What preparation is included: cleaning, rust treatment, fixing replacement, sheet replacement?
Which details are treated, and how: laps, fixings, skylights, gutters, penetrations?
What system and thickness are specified?
How long will it take, and will operations be affected?
What guarantee is offered, and what does it exclude?

A quote that looks cheaper often leaves out preparation or detailing, and those are what make waterproofing last.

Rooftop Solar and Waterproofing

Many commercial roofs in South Africa have added solar arrays in recent years, and they create two waterproofing issues. First, each mounting bracket is fixed through the roof, adding hundreds of new penetrations that must be sealed properly. Second, once panels are installed, the roof underneath is hard to reach, so any future leak becomes much more expensive to fix.

If solar is planned, survey and waterproof the roof first, then install the panels. Agree in writing who is responsible for sealing each bracket and keep a record of it. If solar is already installed and the roof is leaking, the waterproofing contractor and the solar installer should coordinate, because some panels may need to be lifted to treat the roof beneath.

Budgeting for Roof Waterproofing

Roof work tends to be reactive: a leak appears, a contractor is called, a patch goes on. Planned work costs less over the life of a building.

Know what you have. A roof survey records condition, area and problem areas, giving you a baseline for budgeting.
Phase large roofs. Restore the worst sections first and spread the rest over one or two budget cycles, rather than waiting to fund everything at once.
Restore before you have to replace. Waterproofing a sound roof extends its life; waiting until sheets rust through turns a restoration into a re-roof.
Include maintenance. Budget for gutter cleaning and periodic inspections as well as the waterproofing itself.
Document everything. Specifications, photos, guarantees and maintenance records support insurance claims, tenant discussions, valuations and future budgeting.

Insurance and Documentation

Commercial property policies generally respond to sudden damage, such as a storm event, rather than gradual deterioration or poor maintenance. The details vary, so read the policy wording and speak to your broker. In practice, insurers look more favourably on owners who can show the roof was maintained. Keep dated inspection reports, photos of the roof before and after work, invoices and guarantee documents, and report storm damage promptly with photos and a written assessment from a roofing contractor.

Considerations by Building Type

Warehouses and distribution centres

Large uninterrupted roofs with long sheet runs, end laps and box gutters. Stock below is the main risk, so phasing around racking and deliveries matters.

Factories and processing plants

Roofs may carry extraction ducts, vents and plant, and some environments are corrosive. Work is planned around shifts and shutdown windows, and flame-free application avoids hot work risks.

Office parks and retail centres

Mostly flat concrete roofs with plant rooms and aircon units. Tenants and customers below mean low noise, low odour and minimal disruption are priorities.

Apartment blocks and complexes

Flat slabs, parapets, box gutters and balconies over occupied homes. Communication with residents and a clear programme through the managing agent help the job run smoothly.

Roof Inspection Checklist for Facility Managers

Use this checklist for your own walk-round inspections between professional surveys. Only go onto a roof if you are trained and equipped to work at height, and never walk on asbestos or fragile sheeting or skylights.

From inside the building

Stains or drips on ceilings, purlins, racking or stock
Daylight visible through fixings, laps or around skylights
Rust on purlins or the underside of sheeting
Condensation dripping on cold mornings, which is different from a leak

From the roof or a safe vantage point

Blocked gutters, box gutters and outlets, and signs of overflow
Rust at laps, fixings, cut edges and around old drilling swarf
Missing, loose or rusted screws, and perished washers
Cracked or lifted skylight seals, flashings and ridge caps
Ponding water on flat roofs and cracked or blistered membranes
New penetrations from solar, aircon or ducting that may not be sealed
Storm or hail damage such as dents, cracked sheets or debris

Record each inspection with the date, findings and photos, and act on small problems before the rainy season.

Roof Coatings and Building Heat

Large metal and concrete roofs absorb a lot of heat from the sun, which makes warehouses and offices underneath harder to keep comfortable. A light-coloured, reflective roof coating reflects more of that energy instead of absorbing it, which can reduce how hot the roof surface and the space beneath it get, and lower the load on cooling systems. The size of the benefit depends on the building, its insulation and its use, so treat it as a welcome extra rather than the main reason to waterproof. Waterproofing membranes are available in a range of colours, so this can be considered when the specification is drawn up.

Common Mistakes on Commercial Roofs

Patching individual leaks for years on a roof that needs restoring as a whole
Accepting the lowest quote without checking what preparation and detailing it includes
Installing solar or new plant on a roof that has not been waterproofed
Letting gutters and box gutters block, then blaming the waterproofing for overflow leaks
Using torch-on systems over occupied or stocked buildings without proper hot work controls
Not keeping records of what was done, by whom and under what guarantee

All Commercial and Industrial Roof Guides

Every article in our commercial roofs series, including new guides as they are published:

Service pages: industrial roof waterproofing, asbestos encapsulation and epoxy floor coatings. Related guides: roof waterproofing and damp proofing and tanking.

Frequently Asked Questions

Can a warehouse roof be waterproofed without stopping operations?

In most cases, yes. The membrane is applied from the roof, needs no flames, and the spray grade cures almost immediately, so work can usually continue underneath. Large roofs can be phased around operations.

Is restoring a commercial roof cheaper than replacing it?

Usually, when the structure and most of the sheeting or slab are sound. Restoration avoids removal, disposal and new materials, and causes far less disruption.

How quickly can a large industrial roof be waterproofed?

Spray application covers up to 800 m² a day. The total time depends on the size, the preparation and the amount of detailing, and is set out in the programme with the quote.

Who is responsible for the roof in a sectional title complex?

In most schemes the roof is common property, so it is the body corporate’s responsibility. Check your scheme’s rules for exceptions.

Do body corporates need a maintenance plan for the roof?

Under the Prescribed Management Rules, body corporates must have a written maintenance, repair and replacement plan for common property covering the next ten years, linked to the reserve fund. The roof is normally a major item in it.

Can asbestos factory roofs be waterproofed?

Sound, non-friable asbestos roofs can usually be encapsulated, which seals and waterproofs them. Owners should also check their obligations under the Asbestos Abatement Regulations, 2020.

How often should a commercial roof be inspected?

Gutters and outlets should be checked at least twice a year and after major storms, with a professional inspection every two to three years.

Why do torch-on systems pose a risk on occupied buildings?

Torch-on membranes are applied with an open gas flame, which is a fire risk over stock, insulation and occupied spaces and usually needs hot work controls. Cold-applied liquid systems avoid that.

Responsible for a large roof? Contact EcoProof Africa or call 011 894 3535 to arrange a roof survey and written specification.