Why Commercial Roof Refurbishment Is an Opportunity to Upgrade Insulation

When a commercial roof reaches the stage where substantial refurbishment or replacement is required, the waterproofing is often the most obvious concern.

However, roofing works can also provide an opportunity to consider what is happening beneath the waterproofing layer.

Many older commercial buildings have roof insulation that was installed to standards very different from those expected today. In other cases, insulation may have become wet or damaged following years of water ingress.

For building owners, housing providers and property managers, a planned commercial flat roofing refurbishment can therefore provide an opportunity to consider both waterproofing and thermal performance as part of the same project.

Why Does Roof Insulation Matter?

Roof insulation helps reduce heat transfer through the building envelope.

On heated commercial, residential and public-sector buildings, the roof can represent a substantial external area, particularly on properties with large flat roofs.

The effectiveness of the insulation depends on factors including:

• Insulation type

• Thickness

• Condition

• Roof construction

• Continuity of the insulation layer

• Moisture within the roof build-up

• Detailing around penetrations and upstands

When an existing roof is being substantially refurbished, these elements can be considered alongside the new waterproofing system.

Older Commercial Roofs May Have Limited Insulation

Commercial roofs can remain in service for decades.

During that time, expectations around thermal performance and construction standards have changed considerably.

An older roof may therefore contain significantly less insulation than would typically be incorporated into a modern roof build-up.

Some buildings may also have undergone several previous roofing repairs or overlays without the underlying insulation ever being upgraded.

A major refurbishment can provide an opportunity to reconsider the complete construction rather than simply installing another waterproofing layer over what is already there.

What Happens if Existing Roof Insulation Is Wet?

Water ingress doesn't always remain immediately beneath the point where a leak becomes visible.

Moisture can enter the roof build-up and affect insulation beneath the waterproofing.

Wet insulation can lose thermal effectiveness and may affect surrounding materials within the roof construction.

This can become particularly important when deciding whether an existing commercial roof is suitable for further refurbishment or overlay.

Installing a new waterproofing system over a roof containing significant trapped moisture can leave existing problems concealed beneath the new system.

This is one reason why roofing projects often uncover additional problems once work begins, particularly where parts of the existing construction weren't visible before works started.

Does All Existing Insulation Need to Be Removed?

Not necessarily.

The appropriate approach depends on the existing roof construction, its condition and the scope of the proposed refurbishment.

On some projects, parts of the existing construction may be suitable to remain.

On others, deterioration or moisture may mean sections need to be removed and replaced.

Where a complete roof replacement is being undertaken, the new insulation can form part of the overall roof specification.

The important point is that the condition and suitability of the existing build-up should be considered rather than automatically assuming everything beneath the waterproofing can remain.

What Is a Warm Roof?

A warm roof is a common construction used on commercial flat roofs.

In a typical warm-roof build-up, insulation is positioned above the structural roof deck, with the waterproofing system installed above it.

A vapour control layer is normally incorporated beneath the insulation as part of the roof construction.

This keeps the structural deck on the warm side of the insulation and allows the waterproofing, insulation and associated components to operate as an integrated roofing system.

Warm-roof systems are widely used for commercial refurbishment and replacement projects and can be specified with different waterproofing technologies.

Insulation and the Waterproofing System Need to Work Together

Roof insulation shouldn't be considered separately from the waterproofing specification.

The insulation, vapour control layer, waterproofing and associated components form part of the overall roof build-up.

Depending on the project, this may involve built-up felt, single-ply or another suitable waterproofing system.

PRC works with established roofing manufacturers including Bauder, Garland, Langley, Alumasc and Soprema, which offer complete commercial roofing systems incorporating waterproofing and insulation components.

The appropriate system should be selected around the requirements of the individual building.

Building Regulations Can Influence the Refurbishment

Where substantial refurbishment works are being carried out, current Building Regulations may affect the thermal performance required from the roof.

The exact requirements depend on the nature and extent of the works and the existing building.

This means insulation shouldn't be treated simply as an optional extra added to the project at the end.

It may need to be considered while the refurbishment specification is being developed so that the proposed roof build-up is appropriate for the scope of works.

Additional Insulation Changes the Roof Build-Up

Increasing insulation thickness doesn't simply make the roof warmer.

It can also change the finished height of the roof.

That can affect existing details such as:

• Upstands

• Parapets

• Rooflights

• Door thresholds

• Outlets

• Plant

• Pipework

• Edge details

• Flashings

These interfaces need to be considered when developing the new roofing specification.

This is particularly important on complicated commercial roofs containing numerous existing installations.

As we've previously discussed, why rooftop plant equipment creates roofing challenges is often because the waterproofing system needs to interact with equipment that wasn't necessarily designed around the proposed refurbishment.

Insulation Can Also Affect Roof Drainage

Changes to the roof build-up can affect how rainwater moves across the finished roof.

The position and height of outlets need to work with the new roof levels.

Where appropriate, tapered insulation may also form part of a designed falls scheme to help direct water towards drainage points.

However, drainage needs to be considered as part of the overall roof design rather than assuming additional insulation will automatically correct existing falls.

On large commercial roofs, relatively small changes in level can affect substantial areas of the roof.

Upstands Become Particularly Important

Increasing the height of a roof build-up can reduce the effective height available at existing upstands.

This can create challenges around rooflights, parapets, plant bases, access doors and other details.

These areas need to be considered before the final insulation thickness and roofing specification are confirmed.

Otherwise, improving one part of the roof could create difficulties elsewhere.

This is another reason commercial roof refurbishment should be approached as a complete construction rather than simply replacing the visible waterproofing.

Can Insulation Be Upgraded When a Roof Is Overlaid?

Potentially, but it depends on the existing construction and proposed refurbishment system.

An overlay doesn't necessarily mean that the existing roof remains completely unchanged.

However, adding insulation or altering the roof build-up can affect levels, drainage and detailing, so the implications need to be considered across the entire roof.

The condition of the existing roof is also important.

Where widespread deterioration or trapped moisture exists, a more extensive refurbishment may be required.

The correct approach depends on the building rather than whether overlaying appears cheaper initially.

What About Schools and Public Buildings?

Improving roof insulation can be particularly relevant to schools and other public buildings where roofs may have been in place for many years.

However, these projects also need to consider how the building will remain operational while works are carried out.

Removing an existing roof, upgrading insulation and installing a new waterproofing system can require careful phasing and temporary protection.

Our published guide on why roofing projects on schools need different planning explains some of the wider considerations involved when roofing works are undertaken on educational buildings.

What About Housing Blocks?

Housing providers responsible for occupied residential buildings need to consider both the performance of the roof and the practical implications of carrying out the works.

A roof refurbishment may provide an opportunity to improve insulation while addressing ageing waterproofing, but access, residents, scaffolding and programme all need to be considered.

We've previously looked at why occupied buildings need a different roofing approach, particularly where substantial works are being completed while residents remain in the property.

Consider the Whole-Life Value of the Project

A commercial roof refurbishment represents a significant investment.

If the roof is already being stripped or substantially altered, considering the condition and performance of the insulation at the same time can avoid treating the two issues as completely separate projects.

That doesn't mean every refurbishment requires the maximum possible insulation upgrade.

The appropriate solution needs to reflect the building, scope of works, regulations and budget.

But it does mean insulation should be considered while decisions are being made about the new roof rather than after the waterproofing specification has already been finalised.

Commercial Roof Refurbishment Across London, Essex and Kent

Premier Roofing & Construction undertakes commercial roof refurbishment and replacement projects across London, Essex, Kent and the wider South East.

We work on commercial, public-sector and multi-residential buildings, installing built-up felt, single-ply and cold-applied liquid roofing systems from established manufacturers.

Where insulation forms part of the refurbishment, the roof build-up can be specified around the requirements of the individual building and proposed waterproofing system.