What is Engineered Timber?
Engineered timber is a whole industry of structural timber manufactured for a variety of purposes. Engineered timber comes in many forms from prefabricated stud walls, to flat plate floors and walls, cassette systems, CLT (cross laminated timber), LVL (laminated veneer lumber) beams, as well as a variety of other composite systems. The essential aspect is that it is part of a prefabrication process.

Can you explain some of these systems in detail?
Flat plate systems include CLT (cross laminated timber), which are timber planks stacked perpendicular, one on top of the other and held in place by glue. This forms a structural plate from multiple horizontally spanning layers. The system can be used to form walls and floors and a whole building can then be stacked up like a house of cards, which means very quick construction times. The other type of flat plate engineered timber is LVL (laminated veneer lumber) which uses plywood running in cross directions to build up thickness. Flat plate systems replace concrete slabs and in walls can replace load bearing precast concrete or blockwork.

1:(L) CLT (Cross laminated Timber) section. 2:(R) A CLT building under construction 

What type of projects does Engineered Timber suit the most?
Engineered timber can be successful in many building types but, it suits multi-storey residential projects particularly well. In our office, we have just designed a mixed-use project comprising five storeys of apartments, with ground floor retail (see images below). There’s a height limit, of about 15-20 storeys at the moment with engineered timber in most building types. In multi-residential projects, which can be thought of as a lot of houses stacked together, the spans across rooms are relatively small. A flat CLT panel will span this easily and is structurally very efficient. If you don’t have large spans, it’s going to be quite easy to build walls and span up to 5-6 meters with CLT panels. As soon as you go to larger spans you can use LVL beams which have a fantastic bulk aesthetic.

There are design considerations for how architects express engineered timber in their projects. On the one hand a building where the timber is visible, is very honest and relatively cheap because you’re not having to clad it. Timber is also nurturing and good for the soul, so people instinctively like to live in it. On the other hand, engineered timber can really be just a structural system and if it ends up lined with plaster or other more traditional materials, it’s still a good structural material to use, even if some of the tangible material benefit will be missing. Basically, a design isn’t restricted to being a stand-out timber building. Fundamentally, it’s a more sustainable and improved way to build compared with standard blockwork, steel or concrete.

Gardiner Architects design for Mixed use retail and 13 apartments, Thornbury. 3:(L) Internal apartment view 4:(R) Exterior view

What scale of project would it not suit?
In a pure form, it’s not going to suit a very tall multi-storey building. But in a hybrid sense, there are many quite large buildings happening in Europe, especially in England where they’re using engineered timber in developments with over 200 apartments. In these cases you have hybrid systems with, for example, a concrete lift shaft or concrete and steel lower floor podiums and timber CLT panels making up the levels above. As soon as you get into larger buildings they become hybrid systems such as this. This is still great for sustainable design because there is more timber, which is a renewable resource which feels more natural and comfortable to be in.

Would it suit a residential scale? Someone building a new house?
In principle yes. However, the industry isn’t quite big enough in Australia to suit these projects yet. The manufacturing cost currently suits mass production of a lot of panels. The cost of setting up the factory and the CNC machines to make the panels is relatively high, so it’s not terribly economic on a single house project at the moment. But that should change over the next five to ten years.

In terms of construction, it’s economy of scale and time saved currently benefits multi-storey construction. Say you’re doing a concrete slab, you pour it and wait 21 days before you’re allowed to walk underneath and pull the props out. Pour the next one and you’ve got to wait another 21 days. Time efficiencies really start to stack up quickly when you’re using timber.

5:(L)  CLThouse interior. 6:(R) Fitzpatrick + Partners concept design for the tallest timber commercial building in Australia, and is exploring the use of hybrid timber and steel or concrete structures in many of its projects.

 

References:

1.https://www.crosslamtimber.com.au
2.https://i.pinimg.com/originals/23/5e/b6/235eb623986786f2898cf72ce5947d62.jpg
3.Gardiner Architects
4.Gardiner Architects
5.https://www.crosslamtimber.com.au
6.https://www.architectureanddesign.com.au/features/features-articles/timber-buildings-why-and-how-australia-s-poised-to/