The Comer Group is to develop up to 530 apartments in Sandyford Business District, Dublin 18, finally completing a half-finished tower that has marked the Dublin skyline for over 15 years.

Comer will begin building work on 428 units at the Rockbrook site that it purchased from Ires Reit recently, according to The Business Post.

Crucially, that site is connected underground to the adjoining Sentinel office shell structure, which has been part-completed for a decade and a half, where Comer intends to build a further 102 apartments.

The two properties were originally part of a plot being developed by Cork-based John Fleming in the 2000s after his company, Tivway, paid €245M for an 11.3-acre Sandyford site, with the tower set to be at its centre.

Work began on the Sentinel in 2007, but the following year construction halted with Tivway in financial trouble and just the outer shell completed. After the Supreme Court rejected a rescue plan for Tivway, the company collapsed in 2010 owing banks more than €1B.

The Comer Brothers bought the Sentinel in 2011 for just €850K and originally intended to redevelop the tower as 300 office suites, but lacked access to, and ownership of, its part of the basement car park, which runs under both sections of the overall site.

As a result, it has been left as an unfinished shell for a decade.

There were hopes that the site would be unlocked when Ires bought Rockbrook in 2015 and obtained planning permission in 2019. However, construction was delayed, at first by the coronavirus pandemic.

Now, the tower will finally be developed.

The new Rockbrook apartments will be built in two blocks ranging in height from six to 14 storeys, while the site also adjoins Sandyford Central, where Richmond Homes is nearing completion of 564 apartments across six blocks ranging in height from 10 to 17 storeys.

Recently, Dun Laoghaire-Rathdown County Council rezoned the Sentinel structure from offices to residential and Comer is currently in pre-planning discussions with the council.

"When the Rockbrook site came up for sale we saw it as an opportunity to provide basement access to our Sentinel site, we took this opportunity and are now gearing up to start construction in the next few months,” a spokesperson for Comer said.