Japanese architect Kengo Kuma has added a wooden building with a pointy metal roof to a seaside hotel complex he completed five years ago in Nagasaki, south-west Japan (+ slideshow).

The third project on Dezeen this week by Kengo Kuma and Associates, the Royal Terrace building was designed as an extension of the Garden Terrace Nagasaki hotel, which opened in 2009.

It includes new guest suites, all boasting views out over the bay, as well as new restaurant and bar facilities.

The original concept for the hotel involved combining three types of volume – a big box, a small box and a linear block. For this new building, the firm has paired a rectilinear structure with an asymmetric roof, creating two contrasting elements.

"Here we converted the 'hotel as a box' into a 'hotel as a house', by using the roof as the architectural vocabulary," said the team in a statement.

Like the main hotel building, which uses timber as both a construction material and a cladding, the 1,660-square-metre Royal Terrace building was predominantly built from wood. However the roof has a steel surface and framework, and its projecting edges are supported by slender metal beams.

A long wall of glazing marks the building's entrance, while a matching strip of glazing behind allows views through to a courtyard at the building's centre.

The reception is dressed with a zigzagging desk and geometric furniture. A high-level triangular window throws light across the textured walls, which were created using washi – a traditional Japanese paper.

"Its surface possesses the expression of Chinese landscape painting, and with its trace of hand-drawing, we tried to overturn the conventional image of 'coating the wall' with paint," said the firm.

Different designs were applied to the various hotel suites, but most open out to balconies with a view of the bay.

The Teppan-yaki restaurant serves Japanese cuisine, with space for up to 26 diners. A long table stretches across the dining room, directing views towards the harbour through a long window.

An accompanying wine bar is divided by louvred partitions that conceal lighting fixtures, while the bar itself is set against a black backdrop broken up by a strip of wall-mounted wooden offcuts.

Between designing the main hotel and this new annex, Kengo Kuma and Associates has also completed a Garden Terrace hotel in Miyazaki.

Photography is by Fujinari Miyazaki.