Limits of raw timber design
Saving old timber
Antepavilion 2021 - The Sellout
More coming soon
Public House has been focussing on design using raw timber. Still used commonly in small residential projects, timber is very quickly replaced with steel construction or engineered timber (glulam and CLT) as projects become bigger. Public House has been exploring the limits of design using raw timber - it is cheap, low carbon, easy to work with and has a high reuse value when dismantled.
By designing timber trusses, flitch beams (steel plate between two timbers) and built-up members, we have been able to replace steel elements almost everywhere in our design practice, with many beautiful, cost-effective and sustainable design results!
The above comparison demonstrates the carbon benefit of using timber over steel. Public House have designed variations on these alternatives to steel beams for many projects to date.
Moreover, timber has a significant weight advantage making it much easier to work with. At Waking Life Festival in June 2024, we constructed two large bathing pontoons by ourselves, prefabricating parts that could be lifted into place by hand, and screwed (and unscrewed) together.
Too often, steel is used in situations where it is not required. In the example above, the steel beam can support an equivalent residential floor load of 3m width over a 4m length! A typical timber roof rarely sees loading requirements above this. Only for heavier floor loads or very limited headroom does the steel beam become relevant.
We have used built-up members and flitch beams to good effect in a number of projects, replacing steel beams. For one large loft conversion, we designed cranked timber/steel flitch beams, with a cost advantage and no loss of headroom. By connecting timber joists to plywood flooring, the two elements can act compositely to carry more load and replace the need for deeper or additional beams.
On occasions, we have also designed and specified glulam beams. Glulam beams are readily available in the UK and straightforward to specify. From a sustainability perspective, the additional processing to cut-plane-glue the members increases embodied carbon over the raw timber alternative, but is sometimes required to reduce the structural zone.
Finally, we have been exploring timber trusses. Timber trusses allow us to span further than glulam beams, with even more opportunities to replace steel structures. We have designed trusses spanning over ten metres, typically around 1m deep, with the greater depth improving efficiency. Timber trusses are the cheapest and most efficient way to span larger distances. In the projects we have developed, the required structural zone can be incorporated into partition walls or double-height spaces as exposed features. The key to timber trusses are the connections, which often drive member sizes and aesthetics, with steel or plywood plate connections sometimes required. The design effort on developing clean connections is outweighed by the cost, construction efficiency and weight savings of the truss.
Our research is ongoing - we are now looking at using standard lengths of raw timber to create trussed space frames that are cheap and easy to construct and de-construct, for exciting and innovative temporary structures and more.