UC4 Joists

UC4 Softwood Joists for decking

UC4 timber, or Use Class 4, can be used as timber joists and may be exposed to permanent wetting. They are graded as treated  C16 timber and provide exterior structural support. Because most decking timber frames sit at ground level it makes sense to use UC4 joists.

What makes incised UC4 timber joists so special?

UK grown spruce timber grades to C16 which is suitable for most structural applications. The timbers are kiln dried and machine scanned before pressure treatment takes place. This ensures that sufficient preservative is absorbed by the timber for UC4 grading.  

UC4 joists are incised to absorb more preservative than normal house joists. When the timber is incised a bladed machine makes tiny incisions in the surface of the timber. The numerous incisions means that the preservative treatment can penetrate further into the timber. This helps increase the service life of the joist without affecting structural integrity.

UC4 C16 Timber Joists, Posts and Sleepers

Our current UC4 range is all C16 timber with 4x2 at 3.6m/4.8 metres and 6x2 at 3.6m/4.8 metres. Also stocked are 100mm x 200mm sleepers and incised posts from 75mm to 200mm.

Best practices for UC4 timbers

UC4 Posts are installed as per standard posts - post holes 450mm deep and then follow manufacturers instructions for Remix or Post Crete. Plan your decking sub-frame so that only UC4 timbers are in ground contact and always use a recognised end-grain treatment. We also stock all the fixings you need for your UC4 Joints. Any enquiries to Contact Us