Wooden Annex London House Renovation, Tsuruta Architects, Modern English Property Photos

Wooden Annex by Tsuruta Architects, London

15 Sep 2021

Design: Tsuruta Architects

Location: London, England, UK

Photos by Tim Crocker

Wooden Annex London House Extension

Tsuruta Architects fully refurbished the existing 1950’s end of terrace house and extended it with the addition of a single-story timber annex. The large garden came with 9 different adjacent landowners and three beloved mature trees, all of which influenced the proposal. The tree root protection zones on the site determined the use of screw piles and the consequent idea of an entirely timber building, including the foundations.

The client’s wishes didn’t initially fit with the existing long and narrow site. They wanted to be able to interact with people in the dining area as well as in the living room whilst cooking in the kitchen. So we placed the kitchen next to the living area through a new large side opening from the existing house and the dining area positioned in front of the kitchen, projecting it out of the main house and setting it in the garden.

The main house was reconfigured with the insertion of new stairs which significantly improved the circulation to the upper level and provides more spacious bathrooms.

Tsuruta Architects have customised the structure and set out the construction sequence at the design stage instead of using the more common CLT system, a method prepared by a manufacturer or a conventional wood frame system. Our structure, a slab-on-stud arrangement uses a waffle slab fabricated from plywood sheets that span in both directions. This reduces at least 30% of the volume of timber used to form the roof compared to traditional timber joists or a CLT slab.

Between the posts, a ply-formed cassette that contains insulation and a vapor sheet is inserted for bracing, built using a prefabricated flat-pack assembly method. This structure is laid over the acetylated wood foundation ring beam which avoids the need for concrete foundations.

The same wood was used to form the external envelope, posts, feather edge boards, windows, and even roof copings, which allowed for the sharing of off-cut pieces between components. Over 1222 individual pieces were produced digitally for the structure and envelope which were assembled on-site using traditional carpenters skills.

If the annex had been built using conventional brick and steel construction then the embodied CO2 would have been 70%* more, it also used less timber in comparison with conventional methods. Our positive step is marginal, however, small domestic projects dominate the majority of the UK construction output, so the communal contribution could be significant.
*10386 Kg Co2 (brick+ steel+ concrete footing version) against 3075 Kg Co2 (Wooden Annex)