When rodents appear during or shortly after building works, the issue is not always poor cleanliness or waste management. Sometimes, the real cause is much more structural.

Small gaps around pipes. Redundant service holes. Damaged drain connections. Cable routes that were never properly sealed. These are the entry points that can be easy to miss on a busy refurbishment project, especially when the focus is on programme, finishes and getting the space handed back over.

For facilities teams, landlords, builders and commercial property managers, this matters because rodents do not need a large opening. BPCA guidance notes that mice can enter through gaps of around 6mm, while rats can gain access through gaps of around 15mm. That makes seemingly minor defects around services worth taking seriously. BPCA’s mouse prevention guidance and rat prevention guidance explain why low-level gaps, pipe penetrations and poorly protected access points should be checked carefully.

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Why Rodent Entry Points Get Missed During Building Works

Refurbishment projects move quickly. Multiple trades may be working around the same areas, and openings are often created for legitimate reasons: new pipe runs, cable routes, HVAC changes, drainage adjustments or old service removal.

The problem begins when those openings are not reviewed from a pest prevention perspective before the works are closed up.

A small gap that looks insignificant to a contractor can become a repeat access route for mice. A drain issue that does not affect immediate function may still provide a pathway for rats. BPCA’s guidance on site-specific pest risk assessments specifically identifies pipes, cables and open-ended conduits as routes pests can use to enter buildings, advising that these areas should be checked and gaps sealed.

For commercial buildings, these risks often show up around:

• plant rooms

• risers

• service cupboards

• kitchens and tea points

• loading bays

• bin stores

• toilet blocks

• drainage runs

• ceiling voids and raised floors

That is why pest prevention should be considered alongside commercial plumbing and drainage, HVAC and ventilation works and general refurbishment planning.

1. Gaps Around Pipe Penetrations

Pipework is one of the most common places to find missed rodent entry points.

The issue is not the pipe itself. It is the annular gap around it where it passes through:

• external walls

• floors

• service cupboards

• kitchen units

• WC boxing

• plant room partitions

• risers

• meter cupboards

These gaps often sit out of sight, especially behind units, under sinks or inside boxed-in areas. During a refurbishment, a contractor may focus on installing or rerouting the pipe successfully, but not always on whether the surrounding opening has been properly sealed afterwards.

BPCA advises that gaps around pipes should be eliminated as part of rat prevention, and its pest risk assessment guidance also highlights pipes and cables as frequent routeways into buildings.

What to check

Before units are fitted or boxing is closed, check:

• under sinks

• behind kitchen cabinetry

• around boiler or plant pipework

• where water, waste or heating pipes enter walls

• service risers on each floor

• pipe penetrations through suspended or solid floors

If you are already reviewing a property ahead of office or commercial works, this pairs well with the checks covered in signs of rodents before a kitchen or office refurbishment starts.

2. Redundant Service Holes That Are Left Behind

A refurbishment often removes as much as it installs. Old pipework, redundant cables, legacy air conditioning routes and outdated service runs may all be stripped back.

The trouble comes when the opening remains after the original service is removed.

A cable may no longer be used, but the hole it passed through remains. A pipe may be taken out, but the core-drilled opening is left hidden behind plasterboard or a cabinet. These are exactly the sort of defects that are easy to overlook during a fast-moving project.

BPCA’s risk assessment guidance warns that open-ended conduits supplying pipes or cabling from outside can represent a significant risk of pest ingress.

Why this matters

Redundant holes can be particularly problematic because they may:

• connect internal spaces to external voids

• link plant areas to occupied rooms

• provide hidden routes between floors

• sit behind new finishes where they are difficult to revisit later

Once walls are decorated, cabinets are installed and ceilings are closed, the cost and disruption of resolving the issue increases.

3. Drains and Defective Below-Ground Routes

Drainage is one of the most important areas to consider when rodent issues are persistent or keep returning.

A building may appear well sealed at surface level, but rodents can still access it through defective drains, open connections, poorly capped redundant lines or drainage defects linked to WCs and service areas. BPCA’s drainage inspection guidance explains that rodent problems can sometimes be traced back to drainage routes and that incorporating drainage checks into investigations can help solve problems more permanently.

This is especially relevant in:

• older commercial buildings

• offices with repeatedly affected kitchens or toilets

• pubs, restaurants and hospitality spaces

• buildings undergoing major fit-out works

• sites where previous tenants altered layouts or drainage runs

Commonly missed drainage-related risks

Watch for:

• redundant pipes not fully capped

• defective drain covers

• broken or poorly connected waste lines

• flexi pipe routes behind WCs

• access around service penetrations into floor voids

• drainage alterations during refurbishment that are not reviewed from a pest risk angle

For buildings with recurring issues, a pest contractor may need to work alongside a drainage specialist rather than treating the visible symptoms only. That aligns naturally with Barry Turner and Son Ltd’s wider commercial plumbing and drainage services.

4. Cable Entries, Ducts and Data Routes

Modern commercial buildings rely on far more than visible electrical sockets. Data cables, telecoms, access control, fire alarm infrastructure and other low-voltage systems all require routes through walls and floors.

Where several services enter through the same zone, gaps can be left oversized or poorly finished. BPCA specifically identifies pipes and cables as routeways that pests can follow into buildings, particularly where open conduits or poorly sealed penetrations remain.

Areas worth checking

Look closely at:

• comms rooms

• risers

• wall penetrations behind trunking

• external service entry points

• loading bays

• plant areas

• office tea points where multiple services converge

This is particularly important in larger offices and commercial workspaces, where hidden service routes can cross multiple rooms or floors.

5. Gaps in Plant Rooms, Utility Areas and Service Risers

Plant rooms and risers are often functional spaces rather than polished spaces, which is precisely why small gaps can go unnoticed.

They may contain:

• pipework

• ventilation ducts

• controls

• access panels

• lagging

• drainage outlets

• electrical services

• penetrations between internal and external areas

Because these spaces are rarely customer-facing, minor defects can stay in place for years. During a refurbishment, they may also become busier than usual as trades adjust or replace systems.

A practical pest review should not focus only on front-of-house rooms. It should include these lower-profile service zones as well. BPCA’s guidance on pest risk assessment reinforces the importance of inspecting pipes, cables and other structural access routes rather than relying only on baiting or visible signs.

Why Builders and Project Teams Miss These Areas

The issue is not usually carelessness. It is often timing and responsibility.

On a commercial project:

• one trade creates the opening

• another trade uses it

• a third trade finishes around it

• nobody is explicitly responsible for pest proofing it

If the scope does not state who checks service penetrations before closure, the gap can simply survive the project.

This is why facilities teams and project managers should build the question into the programme:

Before walls, risers, floors or boxing are closed, has every service opening been checked for pest ingress risk?

That one line can prevent a lot of trouble later.

What Good Rodent Prevention Looks Like During Refurbishment

A sensible approach is not about sealing every gap blindly. It is about identifying genuine routes and dealing with them properly.

Good practice usually involves:

• checking low-level gaps first

• reviewing pipe, cable and duct penetrations

• assessing redundant services

• looking at drainage issues where rodents are suspected

• using durable proofing methods suited to the location

• documenting areas checked before closure

• escalating anything suspicious before final finishes go in

BPCA’s proofing guidance makes clear that pest prevention is most effective when it is properly assessed and not treated as a last-minute cosmetic task.

Waste and site housekeeping also matter. HSE advises construction teams to plan how waste streams will be managed and who is responsible for collection and disposal, which supports better control of site conditions during works. HSE’s construction waste management guidance is useful background for project teams managing refurbishment sites.

A Practical Pre-Closure Checklist

Before closing ceilings, boxing, risers or service panels, ask:

• Are there gaps around incoming or outgoing pipework?

• Have redundant holes been sealed?

• Are cable and duct entries properly finished?

• Are floor penetrations visible and checked?

• Have service cupboards been inspected?

• Are plant rooms clear of unnecessary debris?

• Is there any sign of droppings, gnawing or nesting material?

• Has any recurring rodent activity prompted a drainage review?

• Has responsibility for final proofing been assigned?

This type of check works especially well when combined with broader project planning, as covered in pest control during renovation.

When to Bring in a Pest or Drainage Specialist

Bring in specialist support when:

• rodent activity has already been found

• the issue keeps returning after treatment

• the suspected route is linked to drains

• large areas are about to be closed up

• the building has a history of infestations

• you are refurbishing kitchens, WCs, basements, bin stores or plant areas

• there are signs of activity but no obvious surface entry point

BPCA’s drainage article makes the case that drainage inspections can be an important part of resolving persistent rodent issues rather than simply treating what is seen inside the building.

Final Thoughts

Rodents rarely need a dramatic opening to get into a building. More often, they use the small, practical weaknesses left around services: pipe gaps, drainage defects, redundant holes and unfinished penetrations.

These are exactly the areas that can be missed during refurbishment because they sit between trades and outside the most visible parts of the project.

For commercial sites, the best time to act is before those areas are boxed in, covered over or handed back to the occupier. A few targeted checks at the right stage can prevent delays, repeat pest issues and costly rework later.

Planning a refurbishment or commercial building upgrade? Barry Turner and Son Ltd can help coordinate wider project works through its commercial services and free quotation service.