Timber: the Building Material of the Future RIBA Work Stage 2 - Procurement Strategy Specifications and Construction Strategy - Swedish Wood

Wood is the greenest building material known to man and the great thing about it is its ability to absorb carbon dioxide from the atmosphere and store the carbon in the wood that we used to build buildings with. But that's only true of course if the wood has been grown sustainably. 

Sustainable

The good news for us in the UK is that 83% of all wood we use comes from a certified sustainable source. Certified that is to the FSC or the PEFC standard and nearly 100% of softwood, the principle building material is certified as sustainable. For wood coming in which hasn't got a certificate from FSC or PEFC the good news there is that most of that will be coming from parts of the world, where sustainable forest management is the norm, but certification just isn't very popular.

On top of that the United Kingdom is subject to the EU timber regulations, which places an obligation on those bringing timber in from outside the EU to conduct a form of due diligence on the product to ensure that it is unlikely that that has come from an illegal source. And depending on the level of risk to take necessary measures to minimise that risk.

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Proof | Chain of Custody

Those specifying wood should always ask for proof that it has come from a sustainable source. In most cases that will be via a chain of custody certificate from either FSC or PEFC. In those cases where that's not available the specifier, should ask the supplier to give evidence that due diligence under the EU timber regulation has been performed on the product, to ensure that it comes from a legal source.

Site Certification

Both FSC and PEFC now offer the opportunity for a developer to get their development certified as FSC or PEFC on a site wide basis. You would need to make sure that all your suppliers are supplying material which is either coming from FSC or what they call controlled wood sources or vice versa.

Specifications

Timber frame generally can go up to 7 storeys in height and really suits those buildings which have a regular plan form as they got the building. Timber frame is not very good being a sort of transfer structure where loads are being pushed on one side to the other regularly. Quite often for example on the ground floor and architect may wish to change use from domestic occupancy to retail or something like that and in those situations it is not that unusual to put a steel or concrete podium at that level and then build a lighter weight timber structure on top. That gives us a saving in weight for the foundations and indeed the structure of the podium itself. An 89 mill stud generally will take a building up to about 4 storeys, when you get to 5, 6 and 7 stories, generally for low bearing walls you're talking about 140 mill studs. In terms of the outside of the building timber frame is very good at supporting all sorts of cladding materials from brick to Trespa cladding, to timber cladding and all shades in between.

Lower U-values

As you'll know, open panel timber frame is the most commonly used type of timber construction. Within open panel timber frame however, we can achieve quite a wide range of U value performance. We can do this by applying laminate finishes to the inside or the outside face of the studs or indeed we can pack the stud with higher quality insulation or make a stud wider.

Closed Panels

If it’s a closed panel you're after, we can vary the wall thickness to suit the U value you need for your project. This example has a C stud construction which reduces thermal bridging, it’s filled with expanded polystyrene beads and is faced on both sides with the same cementitious fire board. On the inside we have a service void to put electrical services and then if we move round, we can see the gaskets that when the panels are joined together provide the air tightness required. You only look at this mockup to see how best we can help you achieve the U values and specification you require.

This sample for instance achieves a U value of 0.15. It’s make up from the inside, part cement particle board, a service zone, insulation, structural stud fully insulated, OSB board, external framing and finally a cement particle board with a render finish.

We can do virtually everything for you without the other trades and it's all manufactured in a factory controlled environment. If you want a higher or lower U value, we can give you the panel construction that you need to help you achieve that.

Construction Srategy

When we are considering a different type of timber product, we contact the manufacturer straight away and we get them in as part of the design team. There seems to be this myth that an adversarial relationship between design team and contractor saves money somehow or other, which I’ve never really understood.

If you can include the contractor within initial design meetings, within initial design consultation and set up a meeting which is set up a design environment which is one of a team which is one of people working together and it's just so much more productive.

Timber Design Innovation

It's a productive route turn to construction, that’s got to be a money saving way of building. And so certainly when we're working in timber, we look to bring in manufacturers, timber suppliers at the earliest opportunity. So that we can really understand what the materials are capable of, what they can feasibly do or how they can visibly perform and that way we can really innovate.

The timber industry at the moment really understands that they're on the brink of a phenomenal sea change in architecture and construction, and our experience is that they've been incredibly helpful, incredibly proactive with their products. So, pick up the phone and call a timber supplier who manufacture something that you're interested in.

Fire Risk

For fire safety during construction all new buildings need to comply with HSG-168. The timber industry has produced guidance to help us meet that code, for example this building is a few meters away from an occupied building we have treatments for that. We could treat the gable of the building, we could treat the floors of the building, so when you're at the stage of producing a fire risk assessment the guidance is there to help you.

Properly specified properly constructed in the right circumstances it is a very good building material. However, we have to urge people to follow the steps as we're working through with the Timber Frame Association. Timber Frame is leading the way on information needed for safe sites and for safe construction and for safe designs. So that information is coming through all the time.

A whole series of strategies have been developed by individual manufacturers and the UK timber frame Association, that allows structural timber frames to be used in pretty well any environment including urban environments quite safely. It is important that those strategies are put in place before you arrive on site, so the overall site safety plan can be developed and then adhered to not only by the timber frame manufacturer themselves but all the various subcontractors on the site.