When inner-city living means no space to build horizontally, build up, says developer Roy Ingle.

His R12,5-million development in Cape Town’s central business district has been built on the roof of an existing building.

Ingle tells Engineering News that the development, located on the corner of Loop and Buiten streets, consists of two double-volume loft apartments and a penthouse.

Each residence has a view of either the harbour or Table Mountain from its sixth-storey location on top of the Elkay House office block.

Each apartment is priced at R3,7-million, with the penthouse on the market for R5,8-million – all off plan.

"I thought of the concept in March last year," Ingle says of his novel de- velopment.

The idea was triggered by the revitalisation of the central business district and the lack of open land.

From concept to finish, the project is expected to take 18 months.

Technically, the roof would have to be six storeys high and be flat and strong enough to support another construction, Ingle says.

The development also requires entering into negotiations with the other sectional-title holders and registering an additional title at the Deeds and Registries office.

The apartments are just over 400 m2 each and are double-volumed, and were both initially designed with three bedrooms. But one will have a gym instead of a bedroom at the new owner’s request.

The timbered decks allow access to the plunge pools and a view of the mountain.

Structurally, there were a few challenges for Ingle, and structural engineers TCA Engineers were brought on board to deal with these.

Speaking on behalf of the consulting engineers, Tony Cooksey says that the biggest challenge was to build a three-storey extension on top of a five-storey building with lightweight material.

"We had to use lightweight material and opted for structural steel as well as a lightweight cement-plaster wall called the Space Frame Construction System, which is supplied from Boksburg." He adds that TCA Engineering was able to draw on its seven years of experience in residential property on the Atlantic seaboard.

While much of this experience has been on building on steep mountain sides, the firm also has extensive experience in using structural steel.

Cooksey adds that this experience was mainly during his years in Johannesburg.

But the growing demand for structural steel in Cape Town leads him to believe that there will be further requirements.

Ingle says that structural challenges had an effect on the aesthetics of the apartments.

"We had to take into account the weight loading, which we limited by putting a steel frame into place and using cladding instead of bricks and mortar." The material used, while lightweight, also had to be dense and soundproof.

Due to the views available, the decision was taken to use as much glass as possible.

Possibly the most technically- challenging aspect were the three pools, he adds.

Consultation with the other sectional- title owners was necessary to extend the lift shaft.

"You needed the consent of all the existing tenants.

"We approached the whole thing in a spirit of collaboration, and they appreciate the fact that we are upgrading the building," says Ingle.