Bird-proofing approved for a listed building "under attack" from birds

A listed Glasgow building under attack from birds is to undergo deterrent work to keep them out.

The former Hill's Trust School in Govan is being besieged with birds gaining access across multiple areas of the property, causing sandstone to be covered by poo among other issues.

Old sandstone buildings are particularly vulnerable to this. The stone is soft and porous compared with modern materials, so droppings sitting on a ledge or cornice do not simply wash off — they hold moisture against the surface and accelerate the erosion of the carved detail that gives a building of this age its character. Lime mortar joints suffer the same way, and once pointing has failed, water gets behind the stonework and the damage spreads well beyond where the birds were roosting.

Feral pigeons are entering the roof space and tits and sparrows are also gaining access to the Golspie Street property.

The two problems are different in kind. Pigeons roosting inside a roof void produce accumulated droppings and nesting material in volume, which is the hygiene and infestation concern. Tits and sparrows are cavity-nesting species: they are looking for holes and gaps to build in, and their presence in small numbers is normal behaviour that happens to be inconvenient when the cavity is inside a building's fabric.

Elderpark Housing Association, which owns the office building, has applied for planning permission and listed building consent to carry out measures to stop the winged squatters.

A statement prepared as part of the application said: "The most significant issue identified by a site survey is that birds, including pigeons and smaller cavity-nesting species such as tits and sparrows, are gaining access into roof voids and concealed spaces around the building, fouling these areas with droppings and nesting material and creating an ongoing hygiene and infestation concern."

The statement said access is "occurring at multiple points across the building, including at the rear extension as well as the main building".

Proofing work only succeeds if every access point is dealt with. Closing the obvious gaps while leaving others open does not keep birds out so much as move them to whichever opening remains, which is why applications of this kind are usually preceded by a survey of the whole building rather than a single elevation.

The housing association plans to install bird spikes and mesh in an effort to keep the unwanted visitors away as "the acidic nature of bird fouling poses a long-term risk to the sandstone fabric", according to the statement.

As wild birds, nest and eggs are protected, work would pause if a nest with chicks or eggs is discovered until it is no longer in use.

That constraint shapes the timing of the whole job as well as the method. Contractors installing proofing on an occupied building have to check for active nests before closing an opening, because sealing a bird in or destroying a nest in use is an offence. In practice the work is scheduled outside the main breeding season where possible, with a check immediately before any opening is closed.

Surfaces where the birds perch would see bird spikes installed while openings would be closed with mesh if the planning application is approved.

Spikes and mesh do different jobs and are generally used together. Spikes make a flat ledge uncomfortable to land on and are visible at close range, so their use on a prominent historic elevation is a design consideration in itself. Mesh closes the void entirely, which is the only real answer for a roof space or cavity, and it is the option that least alters the appearance of the stonework when it can be fitted behind an opening rather than across it.

The measures "have been designed to resolve an active bird control problem at EHA Office Building while minimising harm to its historic fabric and to the character and appearance of the Govan Conservation Area", according to the statement.

The B-listed Victorian former school was built in 1874 by James Thomson and has been converted to offices.

Listed building consent is required here because the work affects the exterior of a designated building, and in a conservation area the test is not only whether the fabric is protected but whether the intervention changes how the building reads from the street. A B-listed building sits in the middle of the Scottish categories — of regional or more than local importance — which means consent is needed but alterations that are reversible and carefully sited are generally acceptable.

The application is under consideration by Glasgow City Council.

Bird-proofing applications of this kind are rarely controversial once the case is documented, since the alternative — leaving the droppings and the infestation to continue — damages the very fabric the listing is meant to protect. The council's decision turns on whether the chosen measures are proportionate and reversible, and on whether they can be installed without harming nesting birds in the process.

For the housing association, the calculus is straightforward. A building converted to offices has tenants and staff using it daily, and accumulated droppings in a roof void bring odour, blocked gutters and insect problems along with the damage to the stone. Proofing is a one-off capital cost against an ongoing maintenance one, which is usually how applications of this kind are justified.

Glasgow's built environment gives the issue a wider context. The city's Victorian tenements, schools and warehouses are built almost entirely of the same soft sandstone, and the gap between what owners can afford to maintain and what the fabric needs is well documented, so a case where deterioration can be arrested cheaply and reversibly is one a council is generally willing to approve.