Posi-Joists vs Solid Joists

If you’re in the process of building a new home, extension, garage or virtually any other structure, you might be slightly bewildered by the different options of joist available (first world problems aye). In this blog we’ll go through the difference between Posi-Joists and traditional solid timber joists, including the benefits and negatives of each.

Benefits of Posi-Joists

Service routing: Thanks to their open web design, they allow pipes and electrics to be routed through without any need to drill holes or chop pieces out. This substantially reduces the labour costs you’d pay to your plumber or electrician.


posi joists with servies installed

Photo: MiTek

Weight: Posi-Joists are much, much lighter (around 40%) as they simply use less material without compromising on strength. This allows them to be manually lifted into place, again, reducing labour costs and rental costs of lifting equipment.

: Posi-Joists can span greater distances than traditional solid joists and are inherently stiffer and stronger. This allows fewer joists to be used for the overall project. It also reduces the likelihood of your floor squeaking later down the line.

Quick to install:
Thanks to their lightweight, highly engineered nature, they’re almost always dead straight and extremely easy to install.

Quieter: Not only are they quieter over time due to their lack of creaking, but absorb more sound and vibration than solid joists.

Warmth: The open web design, as well as allowing space for services, also allows you to pack a load of insulation in the dead space to increase thermal efficiency.

Negatives of Posi-Joists

Initial cost: The initial cost per Posi-Joist is more expensive than a solid joist, which can be off-putting. However, when you consider that you will use fewer joists overall, coupled with the reduced labour costs, Posi-Joists can work out cheaper in the long run.

Can’t be modified: Although there is little reason to modify a Posi-Joist (they’re full of holes, why drill more), some are still unaware that once they’re made, they can’t be modified without prior consent from the manufacturer. If you begin notching and drilling into them haphazardly, the chances are they’re now scrap.

Benefits of solid joists

Cost: Solid joists are cheaper, as they don’t require a great deal of specialist equipment to manufacture. If you’re building something simple/small, a traditional solid joist might be more worthwhile.

Can be modified: Drilling and notching are common practice with solid joists, making them relatively easy to work with if you have some contingency changes. That being said, Posi-Joists can be manufactured with trimmable ends.

Negatives of solid joists

It’s pretty much the opposite of every benefit of a Posi-Joist.

  • Heavier
  • Span shorter distances
  • Increased vibration/sound transfer
  • Higher labour costs when service routing
  • No internal space for insulation
  • Prone to creaking over time

If you've decided Posi-Joists are the option for you, you can shop them on our website here...

Or get a custom quote below: 


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