Changes to work converting Stroud's Tricorn House into 44 flats have reignited controversy over the long-empty building, with residents complaining to planners that they've had no voice on the project.

Developers Viladnik Holdings Ltd – for whom Companies House holds no records – are now ruffling feathers over the wellbeing of starlings roosting in ivy that clads the building, the character of PVC windows and a loss of privacy in surrounding homes.

A tribute to Brutalist architecture, Tricorn House, on Westward Road, Ebley, was built on a Y-plan design in 1972 using 192 large, pre-cast concrete sections. Initially home to the Department for Social Security, it has stood empty for more than 20 years - and was dubbed a 'grot spot' by the town's residents.

Despite new love for such architecture, there is little affection in the town: in a report from Stroud Civic Society, the group called for its compulsory purchase, demolition and replacement, adding it is "a daily affront to all who pass by and a shameful testament to the disinterest and irresponsibility of its owners. Tricorn House would be a problematic building anywhere, but it is a disaster at such a crucial location."

Spared the wrecking ball though, work commenced in February at the former Stroud District Council-owned site with the building set to be revamped into 44 flats. And Viladnik Holdings Ltd, who have no obvious online footprint and have been represented in negotiations via an intermediary, then submitted a modified planning application. This includes PVC windows, a bat shed, external alterations, extra parking and a new glazed entrance canopy.

Planners have subsequently received complaints that the work has begun ahead of formal permission.

One neighbour asks: "Why were all residents not given the chance to object to PVC windows being fitted to dirty concrete surrounds?"

Others have alleged they discovered the amended plans "by the back door". SDC has pointed out that the notice was advertised in the local paper, but that the "commencement of building work starting at Tricorn House did not align with the print and delivery dates of SDC news."

"We share the community's concerns," a council statement said. "Bringing this site back into use is a key priority for the council.... The new ownership of Tricorn House presents an opportunity to finally achieve that. We have been in contact with representatives of the new owners of Tricorn House to advise them on their plans for its redevelopment and we have encouraged them to share these plans with the wider community."

However, SDC's own Conservation arm is lukewarm: "I consider that the proposed windows could be better," an officer reported, "and are perhaps a missed opportunity to enhance the building's appearance and, by extrapolation, the setting of the nearby designated heritage assets; nevertheless, any harm would be on the low end of less than substantial, and would have to be weighed up against the public benefits of the scheme."

Amendments for the site work must be commented on by March 8.