Which is better, steel or glulam?

At Buckland, despite being a glulam manufacturer, we work with steel a lot.

We use steel for bracketry and joins and depending on the project it can often be best to use both materials to achieve the finished result. Take for example our recent project for the RNLI which used over 300 individual steel connections!

We tend to find that steel is still perceived as an either/or material choice to glulam, and especially during the initial planning stages for a project, we get asked a lot of questions comparing the two. To help with this we thought we’d try and cover the topic more broadly.

What are the benefits of using glulam rather than steel?

There are several reasons why you might choose glulam over steel or vice versa.

A lot of the time it comes down to aesthetics. Wood has a good variety in choice of colour – depending on the wood you use for glulam you can create a whole spectrum of colours, from the super cool silvery almost bleached white to warmer treacly hues, to dark rich browns. Steel can of course be coated, but you are more limited with the look and the feel you can create with steel, which is where wood can come into its own.

It’s not just colour either, glulam is perfect for long span or curved designs where you don’t want to compromise the aesthetics.

St Johns School, Leatherhead

Does glulam perform better than steel in certain environments?

The short answer is yes it does. In some environments, the properties of wood are better at standing the test of time over steel. Buildings with swimming pools for example such as schools, leisure centres, private residences, often choose glulam.

In moisture and chemical-filled environments steel corrodes more quickly, whereas glulam lasts longer and is lower maintenance. The same is the case if you are in a seaside location – all the salt in the air from the water around you can play havoc with steel.

It does depend on the purpose of your project. If the glulam is for purely external purposes, you’d need to use hardwoods for durability, which can represent a bigger cost jump from softwoods. Steel has a galvanised finish which generally performs better for external structures; wood by its makeup is more porous and can end up with ‘little visitors’ moving in. Often if used for external projects glulam is chosen because of aesthetics rather than any performance advantage.

Which is more vulnerable to fire?

While it might seem odd to think wood would perform well in a fire, given that is what we put in our log burners, big glulam beams and frames perform very well in fires compared with steel.

Steel needs to be protected by being boxed in or coated in an intumescent paint, otherwise it distorts and buckles in high temperatures. The surface of timber however will char at a known and predictable rate which means when designing a project, it is possible to design glulam to have a certain time of fire resistance. You don’t have to apply any further materials, but you can include additional fire protective finishes on top to further increase the fire performance if you want a belt and braces approach.

Is glulam more expensive than steel?

The answer is sometime yes, sometimes no. To work this out it is best to try and compare like for like as much as possible, here are a couple of examples comparing glulam frames.

Example 1 – 2020 costings

Using a standard 40 x 20m portal frame such as this one below the costs are as follows:

Steel                 £90 per square metre for design supply and installation 

Glulam              £150 per square metre for design supply and installation

Example 2 – 2022 costings

For the design and supply of a smaller 5m span 260 square metre portal frame building the costs were much closer, as follows: 

Steel                 £305 per square metre for design and supply 

Glulam              £330 per square metre for design and supply

How much are steel beams vs glulam beams?

For a simple beam, spanning between supports, glulam is often cheaper than steel. There are also hidden savings due to the ease with which you can fix joist hangers, etc. to the beams, and the fact that you don’t need to box the glulam in as you would do with steel.

Example 3 – 2022 costings

A recent comparison of supply of one beam in glulam (140 x 400 x 6200mm) vs the equivalent strength beam in steel (254 x 146 x 31 UB) yields costs as follows:

Steel                 £370

Glulam             £322

In this case we can say that glulam is the cheaper option, even without the additional costs on the steel of boxing in and fixing the joists.

Glulam is competitive with steel on the beam only comparisons, it’s the fabrication of joints that make the glulam structures describe above more expensive. However, as glulam joints and designs are refined (as steel frame portals have been over many decades), we think the prices of glulam frame buildings will become more competitive over time.

Rawlings

Which is the most sustainable?

Glulam’s main component is of course wood, which can be sourced from sustainable and locally grown sources to help keep the carbon cost of a project down (see our blog on low embodied carbon). Steel on the other hand is mined and subsequently put through to high energy demand manufacturing processes.

We cover ‘Cradle-to-Gate’ embodied equivalent carbon dioxide emissions for both materials on our environmental benefits page. 

Is glulam as strong as steel?

Yes, in fact when you examine the strength to weight ratio, glulam is around 3 times stronger than steel! Apart from the obvious, this also means it’s a beneficial material to work with when installing structures – manoeuvring beams into a roof space for example or craning large elements become more feasible. Another advantage of this is that you can have smaller foundations due to the reduced weight of a frame.

Steel does have a much higher allowable stress, so steel members tend to be smaller than the equivalent glulam member, but the glulam is usually lighter. Please refer to our load span tables for more information.

We’ve a rule of thumb that the glulam needed to do the equivalent job of a steel is between 1.5 times and 2 times the depth, so if headroom is tight sometimes steel is the better option.