The use of I Joist beams on the roof allows for high performance insulation with near zero heat loss

Wood has always been used in construction. With its pluses and minuses, it has fitted in well with the requirements and helped to build solid constructions. With industrialisation, wood was processed and so the pluses became more and more. One result of this advanced processing is the so-called I Joist. They have been designed to withstand high loads as a building material used in all areas of structural construction. Their specific shape allows them to support similar loads at a much lower weight than wooden beams of the same dimensions. They are used in the construction of ceilings and roofs, or as wall studs. houses on wooden structure. Their use is very suitable for energy efficient buildings and passive cell.

About I Joist

I Joist beams were invented in 1969 by Trus Joist Corporation (TJ) in the USA. Immediately the construction market embraced the idea and a host of other manufacturers and variants emerged. Architects also welcomed the idea because the beams created the possibility of building wide open spaces. Later, environmental and energy-saving requirements led to their use in energy-efficient construction because they reduced costs and labour. For example, in the case of ventilated facades and walls thicker than 350 mm open to diffusion, the use of I Joists replaces the more elaborate and expensive construction of a thick wall in solid profiles.

The beams were originally built from a central part of OSB and two sides - soles - made of solid wood finger-jointed or plywood, glued with a moisture-resistant adhesive to the central part. The whole assembly forms an I-shaped profile, hence the name. Later variants appeared in which plywood was replaced by LVL (read more here) and/or OSB with fibreboard.

I Joist beams are produced in factories with different sizes for the footings and the central part. They can have very long lengths, while remaining equally rigid and secure. The length can be adjusted on site according to project requirements.

Advantages of using I Joist beams in construction

The main advantage of I Joist beams is that are much easier than wooden beams of the same dimensions, provided they bear the same loads. They reduce the pressure on the construction, which saves on foundation construction. Also, ceilings and roofs built with such beams do not need oversized walls to support them. Because they are lighter, they are easier to handle and can even be assembled by a single worker, which is impossible with a full beam. Assembly is faster and more efficient.

Does not warp, crack or vary dimensionally. Wood can crack, warp or change in size with changes in humidity. This is what can happen with solid beams. With I Joist beams these problems have been eliminated, as industrialised timber is much more stable and safer.

Allows large openings to be made at low cost. Wide open spaces are much brighter and more inviting. They can only be achieved if the strength structure allows it. One option is to use laminated beams, which are very strong but much more expensive. Large openings can be made with I Joist beams, which are just as strong, but at much lower cost. They are very suitable for building such loft spaces without pillars to spoil the design.

Solves the problem of creaking floors in wood-frame houses. Being very rigid and fixed, the floors will behave as a whole, with no elements moving and rubbing so that the specific creaking occurs.

Makes it easier to fit installation routes, which can be passed through the beam. All electrical, plumbing or gas routes can pass through the I Joist. They do not need to be cut to fit, as is the case with solid beams. This reduces costs and labour.

Enables energy-efficient construction at lower cost and helps reduce thermal bridges. The insulation of floors and roofs where I Joist beams are used is very efficient. Insulation is achieved without the addition of spacers, as with solid beams, and heat loss is reduced to almost zero.

Reduce consumption of solid wood. The reduction in consumption comes from the smaller size of the beam compared to a solid wood or laminated beam for the same load-bearing capacity and from the use of OSB which is much more efficient in the use of wood, with a much better yield.

As you can see, a lot of advantages. It's also the reason why they are increasingly used in timber construction. We also looked for mentions of the disadvantages. The only one was the one about fire resistance, which is lower than that of laminated wood beams. But this too can be solved by specific fireproofing treatments.

I hope you find the information useful. If you have any additions, please leave them in the space below. That way we will have a complete material, useful for everyone.