Why Low-Odour Liquid Waterproofing Matters on Occupied Commercial Buildings

Roof refurbishment does not always take place on an empty building.

Offices, schools, residential blocks, healthcare facilities and public buildings may need to remain operational while roofing work is carried out above them. In these environments, the choice of waterproofing system can affect far more than the roof itself.

Some roofing products produce noticeable odours during application and curing. These odours may enter occupied areas through windows, doors, ventilation systems or air-handling equipment, potentially causing discomfort and disruption.

A low-odour liquid waterproofing system can help reduce these effects, but product selection must still form part of a wider plan for protecting occupants and maintaining building operations.

Why Does Odour Matter During Roof Refurbishment?

Roofing products are applied outside, but the effects may still be noticed inside the building.

Odours can travel through:

• Open windows and doors

• Mechanical ventilation systems

• Air-conditioning intakes

• Roof penetrations

• Service ducts

• Stairwells and access hatches

• Gaps within the existing roof construction

• Shared external areas

Even where an odour does not indicate a dangerous level of exposure, it can cause concern among occupants who do not know where it has come from or how long it will last.

In offices and public buildings, this can lead to complaints, interrupted work, rooms being closed or staff being moved unnecessarily.

What Is a Low-Odour Liquid Waterproofing System?

Liquid-applied waterproofing is installed as a coating that cures to form a continuous waterproof layer.

Low-odour systems are formulated to reduce the strong smells commonly associated with some resins and application processes. This can make them more suitable for sensitive or occupied environments.

They may be considered for:

• Office buildings

• Schools

• Residential blocks

• Hospitals and healthcare properties

• Hotels

• Retail buildings

• Public-sector sites

• Roofs containing ventilation equipment

• Balconies and walkways close to occupied rooms

Low odour does not mean that no smell will ever be noticeable. It also does not remove the need for risk assessments, ventilation planning, product information and appropriate controls.

The manufacturer’s guidance and project-specific safety requirements must still be followed.

Why Are Liquid Systems Useful on Commercial Roofs?

Commercial roofs often contain complex areas that can be difficult to waterproof using rigid or sheet-based materials.

These may include:

• Pipe penetrations

• Air-handling units

• Ductwork

• Cable trays

• Plant supports

• Rooflights

• Upstands

• Gutters

• Changes in roof level

• Irregular junctions

A liquid system can be applied around complicated shapes to create continuous waterproofing with fewer joints.

This can make liquid waterproofing particularly useful on congested plant roofs, where access around equipment is limited and the system must accommodate numerous details.

Our guide on why rooftop plant equipment creates roofing challenges explains the wider issues that should be considered.

How Can Ventilation Systems Affect the Work?

Air-handling units and ventilation intakes can draw external air from roof level into the occupied building.

If roofing materials are being applied nearby, odours may be carried directly into offices, classrooms or other internal areas.

Before work begins, the project team should identify:

• The position of all air intakes

• Which internal areas they serve

• Whether units operate continuously

• Whether intakes can be temporarily isolated

• Whether alternative ventilation is available

• Which areas of the roof should be completed first

• Whether work should be carried out outside normal hours

• Who is responsible for changing the building’s ventilation settings

Any alteration to mechanical services should be agreed and managed by the responsible building or M&E team. Roofing contractors should not assume that ventilation systems can simply be switched off.

Does Low Odour Mean the Building Can Operate Normally?

A low-odour product may reduce disruption, but it does not guarantee that the building will be unaffected.

The project still requires careful planning because occupants may also be affected by:

• Noise

• Vibration

• Deliveries

• Scaffolding

• Restricted access

• Temporary closures

• Dust

• Work around windows

• Changes to ventilation

• Movement of materials across the site

The roofing system is only one part of the wider construction programme.

Working areas may need to be phased so that sensitive sections of the building are avoided at particular times. Some tasks may also need to take place during evenings, weekends or periods of lower occupancy.

This forms part of the broader planning required for roofing works on occupied buildings.

Why Should Building Users Be Informed?

Clear communication can prevent unnecessary concern.

Occupants should be told:

• What work is taking place

• Which roof areas will be affected

• When materials will be applied

• Whether a temporary odour may be noticeable

• How long the work is expected to continue

• Which access routes or rooms may be affected

• Who to contact if they have concerns

The information should be proportionate and easy to understand. Technical product descriptions alone may not reassure someone who suddenly notices an unfamiliar smell within their workplace.

Giving notice also allows building managers to identify sensitive activities, events or occupants before the programme is agreed.

How Is the Right Waterproofing System Selected?

Odour is important on an occupied building, but it should not be the only deciding factor.

The proposed system must also be suitable for:

• The existing substrate

• The roof’s condition

• Moisture within the build-up

• The required service life

• Drainage

• Foot traffic

• Plant and equipment

• Fire-performance requirements

• Application temperatures

• Available working periods

• The proposed warranty

A low-odour product that is unsuitable for the existing roof will not provide a successful refurbishment.

The contractor, designer and manufacturer may need to assess the roof before confirming the specification. Read more about choosing a system for commercial roof refurbishment.

What Preparation Is Required?

Liquid waterproofing relies on the condition and preparation of the surface beneath it.

Before application, the contractor may need to:

• Clean and dry the substrate

• Remove loose or defective materials

• Repair cracks and damaged areas

• Replace wet insulation

• Treat corrosion

• Prepare different surface types

• Complete adhesion testing

• Apply suitable primers

• Reinforce joints and complex details

Preparation work may itself create noise, dust or temporary odours. These activities should be considered when planning work around occupied areas.

The roof should also be divided into manageable sections so that preparation and waterproofing can be coordinated safely.

How Do Curing Times Affect Occupied Buildings?

Liquid systems require time to cure before they achieve their intended performance.

Curing time can influence:

• How quickly an area becomes waterproof

• When subsequent layers can be applied

• When the roof can be accessed again

• How long an odour may remain noticeable

• Whether work can be completed within restricted hours

• How weather conditions affect the programme

Some systems cure more rapidly than others, which can be useful where working periods are limited or the building must remain operational.

However, actual curing will depend on the selected product and site conditions. The manufacturer’s instructions must be followed rather than relying on a general assumption about liquid systems.

Why Is Manufacturer Approval Important?

Liquid waterproofing systems include more than the visible topcoat.

They may require specific primers, reinforcement, resins, finishes and preparation methods. Substituting individual products or changing the application process may affect performance.

An approved contractor should understand:

• Which substrates the system can be applied to

• How each surface must be prepared

• Which primers are required

• How details should be reinforced

• Suitable weather and temperature conditions

• Required curing times

• Inspection and record-keeping requirements

• Conditions attached to the warranty

As a WestWood-approved roofing contractor, PRC has experience installing low-odour PMMA waterproofing on complex commercial roofs.

Millstream West: Waterproofing Above an Occupied Workplace

PRC completed a 2,100m² roof refurbishment at Millstream West in Windsor, an active building that needed to remain operational throughout the work.

One roof zone contained air-handling units, cabling, pipework and ducting, while another housed multiple solar panels. Saturated insulation and restricted access added further complexity.

PRC installed WestWood’s Weproof 264 low-odour PMMA waterproofing system to reduce the effect of the works on the occupied offices below.

In the congested plant area, the roofing team coordinated closely with M&E contractors to work around the existing equipment. Damaged insulation was replaced, and specialist detailing was completed around the infrastructure.

The low-odour system, careful planning and coordination allowed the 2,100m² roof to be refurbished without interrupting normal business operations.

When Might Another Roofing System Be More Suitable?

Liquid waterproofing is not automatically the right answer for every occupied commercial building.

Another system may be more appropriate where:

• The existing roof must be completely stripped

• Large uninterrupted areas favour a membrane system

• The substrate is unsuitable for liquid application

• Significant structural work is required

• Moisture is widespread within the roof

• The required specification uses another waterproofing method

• The manufacturer cannot approve the proposed application

The choice should be based on survey findings, building use, roof construction and project requirements.

PRC installs a range of commercial flat roofing systems, allowing the refurbishment approach to be selected around the building rather than relying on a single solution.

Planning Low-Odour Waterproofing Works

Low-odour liquid waterproofing can help reduce disruption when commercial roofing work is carried out above an occupied building.

Its success still depends on proper investigation, substrate preparation, system selection and coordination with the people responsible for the building.

Ventilation intakes, working hours, sensitive occupants and internal activities should all be considered before the programme begins. Clear communication then helps building users understand what is happening and what to expect.