Designing and constructing the wooden interior for the One Main renovation project in Boston, USA is a showcase for an untypical use of Kerto® LVL (laminated veneer lumber). The wavy wooden surfaces that comprise the interior are built entirely from cross-bonded Kerto® LVL panels that are usually used in structural members.

The project’s principal architect, Mark Goulthorpe from dECOi Architects, a professor at nearby MIT, offered a proposal with a greatly streamlined building methodology, where the usual multi-trade, multi-component legacy of late-industrial production was surpassed in a unitary CAD-CAM logic.

Kerto® LVL for wooden interiors

Metsä Wood’s cross-bonded Kerto LVL Q-panel is typically used in structural elements. However, the One Main office in Boston is an excellent example of a completely different way to use the product.

Kerto LVL Q-panels got the nod from dECOi Architects due to its thickness and because it comes in big panels. Kerto is relatively inexpensive, relatively gap-free, and has no long waiting period. It was a pragmatic choice to balance costs, fabrication and aesthetics. The greatest benefits of Kerto LVL are that its raw material is sustainably grown, and that as a large, laminated panel, it readily lends itself to milling that yields a good, strong edge. Given the laminated mass, it can look extremely seductive. If dECOi had reduced the thickness of the laminates, or the panel size, the milling time and cost would have increased exponentially.

Prefabrication speeds up the assembly

Every part of the interior was fabricated off-site with a powerful three-axis CNC machine. The design algorithms divided up the architectural forms into discrete elements that could nestle onto 12 ft × 4 ft (3.7 m × 1.2 m) panels, all automated and optimized by the architectural team. The parts were milled with dowel holes so they could be easily located spatially without requiring much other than sequencing correctly, alignment, and gluing or nailing.

The goal was to minimize labour on-site, and to a large degree this was achieved, as larger and larger finished parts were delivered to site – for example, entire office floors or the reception desk shipped as completed elements that only needed to be positioned on-site.

Since all the elements were milled, the integration of secondary elements such as lights or ventilation was very simple, literally milled into the woodwork - the lights just dropped into pockets in the wood, the vents or sprinkler heads attached with a simple screw.

Wooden dowels for connections

The functional office space is “trapped” between two active surfaces – the floor and ceiling – which are each “animated” by functional attributes such as vents or light housings. The base spatial arrangement is established by the reception desk seeming to rise out of the floor, or by the ceiling being “pulled” down towards the floor for structure, or up to the sky for light.

The narrow wooden pieces were connected with wooden dowels, water-based glue and a nail-gun to attach the parts into laminated elements. This proved to be a quick and easy way to assemble what seem complex parts. The elements were then hand-sanded and sprayed with a matt, water-based varnish. The existing office tower was a 1970s concrete slab building with hermetically sealed windows and full air conditioning. There was plenty of structural redundancy to hang the relatively lightweight ceiling panels from the roof slab.

Curved shapes from flat Kerto LVL panels

It was imperative to streamline the actual milling process for speed and economy. All the visible elements of the design were fabricated as stacked sectional elements cut from flat Kerto LVL panels.
The ceilings, walls, floors and static furniture were all created as striated elements made from layers of Kerto LVL, with functional elements such as ventilation grilles, light pockets and door handles formed by directly milling the wood.

The architects handed over actual milling files – the actual cutting instructions – for fabrication, with the elements already mounted on some 1,200 Kerto LVL panels to minimize waste. The instructions were then issued digitally to the numeric command machine.

Well over one million linear feet of cut were issued, a shift in the base protocol of contracting logic, the architects fully in control of every detail via the fabrication code.

Fire safety with Kerto LVL interiors

The wooden design of One Main could likely have gained fire approval for the ceiling given the size of the members, which char and resist decomposition, but in the interests of expediency the architects ended up double-sprinkling the entire space – one layer of sprinklers at the slab above the ceiling and one projecting through the ceiling.