Choosing the right timber isn’t just about species – the strength class is what tells you how that timber will actually perform on site. But with labels like C16, C24, D30 and D70, it can look more complicated than it really is.
Here’s a quick, easy guide to what those classes mean and which timbers fall into each.
C-Grades: Softwoods for Everyday Construction
C-grades are softwoods commonly used across the UK building industry.
C16 – Pine & Spruce
The most widely used structural timber.
Strong enough for most framing, floors, roofs and general construction.
C24 – Larch & Douglas Fir
A step up from C16.
Denser, stronger and better for longer spans or heavier loads. Ideal when you want higher performance or fewer natural defects.
D-Grades: Hardwoods for Heavy-Duty Use
D-grades are hardwoods suited to tougher environments – rail, civils, marine, and anywhere durability really matters.
D30 – Beech & Oak
Reliable, strong hardwoods used in structural work and engineering applications.
D40 – Iroko & Jarrah
Naturally durable hardwoods with strong resistance to decay, insects and weathering. Used for external joinery, heavy-duty decking, cladding, and outdoor structures.
D50 – Opepe & Keruing
High-density, high-strength hardwoods commonly used in civil engineering, marine applications, and heavy load situations such as beams, bridge elements, industrial flooring, and occasionally sleeper/crossing-timber equivalents.
D70 – Ekki, Greenheart & Balau
The top end of strength classes.
Exceptionally strong and long-lasting – even when submerged. Perfect for marine structures, heavy civil engineering, crossing timbers and extreme environments.
Where Bog Mats Fit In
At Ryder Services, our bog mats are usually made from beech or oak – strong, reliable D30 hardwoods that perform well under load.
We also supply ekki hardwood mats for the most demanding sites where maximum durability and long service life are essential.
Making Timber Selection Simple
Whether you need C16 joists, C24 structural framing, D-grade hardwoods, crossing timbers or heavy-duty bog mats, choosing the right strength class is key to safety, performance and longevity.
Ryder Services can guide you through the options, so you get the right timber first time – with no guesswork.