Waterproofing for Flat, Commercial & Industrial Roofs

A roof can look sound from ground level while water is already finding a way through laps, penetrations or poorly drained areas. Sika roofing systems provide different waterproofing approaches for flat roofs, low-slope commercial buildings, industrial facilities, terraces, podiums & refurbishment work.

Choosing the right membrane starts with how the roof is built & how it will be exposed. Liquid-applied systems suit complex detailing, sheet membranes provide controlled factory-made thickness across larger areas & torch-on membranes suit particular protected or ballasted assemblies.

Australian roofs also face demanding UV, heat, rain & ponding conditions. That makes drainage, substrate condition, membrane exposure & detailing around drains, parapets, services & roof penetrations important parts of the system rather than afterthoughts.

Where the concrete deck needs repair before waterproofing begins, explore Sika Concrete Repair & Protections.

What Are Sika Roofing Systems?

Sika roofing systems combine waterproofing membranes, adhesives, primers, insulation components & accessories used to protect compatible roof assemblies from water ingress.

Depending on the project, the system may include:

► Liquid-applied membranes
► PVC sheet membranes
► FPO sheet membranes
► Torch-on bituminous membranes
► Roof primers
► Membrane adhesives
► Insulation
► Detailing membranes
► Roof accessories
► Protective or reflective top coats
► Ballasted or protected membrane build-ups

Each technology solves the waterproofing problem differently.

Liquid membranes cure in place.

Single-ply membranes are manufactured as sheets & joined according to the specified installation method.

Torch-on products use heat to bond bituminous membrane layers where the roof design allows it.

Which Roofing System Suits the Job?

No one membrane type is automatically better. The right choice depends on substrate, exposure, drainage, roof traffic, detailing, installation method & the complete roof build-up.

Liquid-Applied Roofing

Complicated roof details are where liquid membranes can make their strongest case.

Liquid-applied systems form a seamless membrane over properly prepared substrates, making them particularly useful around:

► Plant penetrations
► Roof drains
► Upstands
► Parapets
► Corners
► Irregular details
► Refurbishment areas
► Complex roof geometry

Sika's liquid-applied roofing range includes systems designed for high-performance roof waterproofing, with compatible primers & accessories selected around the substrate. 

Where Liquid Roofing Can Work Well

Consider liquid-applied roofing where:

► The roof has many penetrations
► Existing detailing is complex
► Seamless coverage is useful
► Refurbishment is preferred over complete removal
► A cold-applied method is required

The substrate still matters. Existing membranes, concrete, metal, insulation boards & other roof surfaces need to meet the preparation & compatibility requirements of the selected system.

PVC & Single-Ply Roof Membranes

Wide roof areas often suit a membrane with controlled manufactured thickness & defined seam detailing.

Sika's Sarnafil & Sikaplan systems include single-ply membranes for suitable commercial & industrial roofs.

Sarnafil G 410-20 L, for example, is a PVC roof waterproofing membrane designed for direct exposure, with hot-air-welded seams plus resistance to permanent UV exposure. 

Sheet-membrane installations can involve:

► Hot-air welding
► Mechanical fastening
► Full adhesion
► Ballast
► Insulation
► Perimeter restraint
► Roof detailing
► Drain connections

For compatible membrane-related accessories, browse Sika | Construction Accessories.

Ballasted & Protected Roof Membranes

Some membranes are designed to work beneath protection rather than remain exposed.

Sarnafil G 476-20, for example, is positioned for ballasted roofs, roof gardens, utility roofs, inverted roofs, balconies, terraces, plaza decks & concrete slabs under compatible protection layers. 

Protected membrane systems can include:

► Gravel ballast
► Pavers
► Roof-garden build-ups
► Inverted roof assemblies
► Plaza decks
► Terrace finishes

The membrane selection needs to match what's going above it.

Torch-On Roofing Membranes

Bituminous torch-on membranes remain a practical route where the roof specification calls for a fully bonded sheet system.

SikaShield includes a range of torch-on products with different reinforcement, thickness & surface finishes.

Current Sika Australia products include:

► Mineral-surfaced membranes
► Talc-finished membranes
► Anti-root membranes
► Separation layers
► Elastomeric bituminous membranes
► Self-adhesive heat-sensitive membranes

Some products are suitable for exposed use, while others are intended beneath protection or another layer.

Check UV exposure before selection. A membrane designed for protected use shouldn't be treated as an exposed roof finish.

Liquid vs Sheet vs Torch-On Roofing

The same roof area can often be waterproofed in more than one way, but detailing & installation conditions can make one system more practical.

Commercial & Industrial Roofs

Large commercial roofs rarely stay simple once services are added.

HVAC units, cable trays, vents, skylights, plant bases & access routes all interrupt the membrane field.

A commercial roofing plan should account for:

► Membrane continuity
► Plant penetrations
► Roof traffic
► Drainage
► Parapets
► Maintenance access
► Thermal movement
► UV exposure
► Future equipment installation

For joint sealing around compatible construction details, Sika | Sealants & Adhesives provides a related range.

Flat & Low-Slope Roofs

The slower water leaves a roof, the more important drainage & membrane continuity become.

Check:

► Falls
► Drain locations
► Overflow routes
► Ponding areas
► Membrane laps
► Upstands
► Roof edges
► Penetrations
► Existing repairs

Persistent standing water can indicate inadequate falls, blocked outlets, deflection or settlement.

A membrane may tolerate ponding, but poor drainage should still be corrected where practical.

Roof Refurbishment

A roof with leaks doesn't automatically need complete replacement, but another patch isn't always the answer either.

Refurbishment can make sense where the existing roof remains suitable for an approved overlay or liquid system.

Before proceeding, inspect:

► Existing membrane adhesion
► Trapped moisture
► Blisters
► Cracking
► Failed seams
► Previous patches
► Drainage
► Substrate condition
► Roof penetrations

Covering an unresolved moisture or adhesion problem can simply hide the failure beneath a new layer.

Roof Gardens & Landscaped Roofs

A landscaped roof adds water, soil, roots & maintenance above the waterproofing membrane.

A compatible roof-garden build-up can involve:

► Waterproofing membrane
► Root-resistant layer
► Protection layer
► Drainage layer
► Growing medium
► Vegetation

Sika offers membranes suitable for ballasted & roof-garden systems where the specified product supports the assembly. 

Roof Membrane Adhesives

The membrane is only part of an adhered roofing system.

Sarnacol-2142 S is one example of a Sika roof adhesive designed for felt-backed Sarnafil & Sikaplan membranes over suitable substrates such as concrete, insulation boards, plywood, metal sheet & prepared bitumen membranes. 

That makes substrate preparation & adhesive compatibility just as important as selecting the membrane roll.

UV, Heat & Weather Exposure

Australian roofs spend much of their service life exposed to sun rather than rain.

Roofing systems may need to account for:

► UV radiation
► Heat
► Thermal cycling
► Wind
► Storm exposure
► Ponding water
► Salt-laden air
► Industrial environments

Where a membrane will remain directly exposed, use a system specifically designed for that exposure.

Sarnafil G 410-20 L, for example, is formulated for direct exposure with UV stabilisation built into the membrane. 

How to Choose a Sika Roofing System?

Identify the Roof Substrate

Start with what's underneath:

► Concrete
► Metal
► Existing membrane
► Timber deck
► Insulation
► Screed
► Another compatible substrate

Decide Whether the Membrane Will Be Exposed

This decision narrows the system quickly.

Will the membrane sit:

► Fully exposed?
► Beneath ballast?
► Beneath pavers?
► Under a roof garden?
► Beneath another protective layer?

Map Every Roof Detail

Record:

► Drains
► Parapets
► Penetrations
► Upstands
► Movement joints
► Roof edges
► Plant supports
► Existing repairs

Check Drainage

A waterproof roof still needs somewhere for water to go.

Confirm:

► Falls
► Outlet capacity
► Overflow paths
► Ponding areas
► Blocked drains

Assess Refurbishment Conditions

Where an existing roof is being overlaid or coated, check:

► Adhesion
► Moisture
► Surface condition
► Previous membrane type
► Compatibility
► Repair requirements

Confirm the Complete System

A roof system can include:

► Primer
► Adhesive
► Insulation
► Membrane
► Reinforcement
► Top coat
► Detailing components
► Protection
► Ballast
► Drainage

Don't treat the membrane as the entire roof build-up.

Surface Preparation Before Roof Waterproofing

A membrane can't correct a substrate that's already failing underneath it.

Preparation may involve:

► Cleaning
► Removing loose material
► Repairing cracks
► Reinstating damaged concrete
► Removing incompatible coatings
► Drying appropriate surfaces
► Checking moisture
► Correcting local defects
► Applying the specified primer

Where concrete repair is required first, use Concrete Repair & Restoration.

For suitable cleaning before compatible roofing or repair work, Sika | Cleaning Agents provides a relevant preparation range.

Expert Tips for Roofing Projects

Start at the Drains

If water can't leave the roof properly, even a good membrane is working harder than it should.

Check falls, outlets & overflow capacity before deciding the waterproofing system.

Detail Every Penetration Individually

A pipe, vent or plant support creates a new perimeter that must stay watertight.

Don't treat penetrations as incidental finishing work.

Match the Membrane to Exposure

Exposed, ballasted & buried systems need different membrane properties.

Confirm where the membrane will sit within the finished roof build-up.

Verify the Existing Roof Before Overlaying It

A refurbishment system only performs as well as the substrate underneath.

Check adhesion, moisture & compatibility before installing over existing material.

Plan Around Weather

Roofing work has nowhere to hide from changing conditions.

Check rain, wind, substrate temperature, dew & curing requirements before application.

Coordinate Related Trades

Roof leaks often start after someone else modifies the finished roof.

Plant, plumbing, electrical & mechanical work should be coordinated so new penetrations are detailed correctly.

Read Safety Information Before Starting

Roofing products, primers & adhesives can have specific handling requirements.

For practical guidance, read How to Read a Safety Data Sheet - A Quick Guide for Workshop Operators.

Prepare for Seasonal Work

Roofing & waterproofing schedules can be heavily influenced by weather.

Spring Jobsite Prep Getting Your Gear Ready provides useful preparation ideas before busy periods.

Look Beyond Material Price

A roof leak can affect insulation, ceilings, equipment & occupied areas below.

The Hidden Cost of 'I Can Get It Cheaper Online looks at purchasing decisions beyond the upfront price.

Roofing Mistakes Worth Avoiding

► Don't use one membrane type for every roof
► Don't coat over unsound substrate
► Don't ignore persistent ponding
► Don't select a protected membrane for permanent exposure
► Don't overlook roof penetrations
► Don't forget parapet & edge detailing
► Don't assume an existing membrane is suitable for overlay without checking
► Don't mix system components casually
► Don't ignore trapped moisture
► Don't assume roof coating fixes poor drainage
► Don't apply during unsuitable weather
► Don't treat a local internal leak as proof of the exact roof entry point
► Don't ignore roof traffic & maintenance access
► Don't substitute general guidance for the current Sika Product Data Sheet & project specification