Timber design
How joists, rafters and timber beams are sized, and when timber can do the job of a steel.
About this topic
Floors, roofs and loft conversions are mostly timber, and small changes in grade, spacing or span direction can save a deeper joist or a steel. This topic shows how the sizes are set and where the savings are.
How it’s sized: Span, spacing, load and strength class set the size. For floors, deflection and vibration usually govern.
What you’ll learn at each level
1
Level 1: FoundationUnderstand the design
- Timber strength classes such as C16 and C24, and what they mean
- Joists, rafters, purlins, binders and trusses: what each does
- Span tables and their limits
- Notching and drilling rules
2
Level 2: PractitionerCheck the design
- Sizing floor joists and rafters from load, span, spacing and deflection
- Trimming openings for stairs and rooflights
- Flitch beams and engineered timber: glulam, I-joists and LVL
- Roof spread, and the role of ties and ceiling joists
3
Level 3: AdvancedChallenge the design
- Loft conversions: new floors, existing roofs and removing purlins
- Strengthening existing timber
- Connections, hangers and fixings
- Timber alternatives that save a steel
Draft outline. The full syllabus is sent with your course details.
Questions that save you money
The kind of question you’ll be able to put to your engineer, and understand the answer to.
- Would C24 instead of C16 avoid a deeper joist or a steel?
- Can the joists span the other way?
- Could a flitch beam or glulam replace the steel?
Who it’s for
Builders & contractorsArchitectsProperty investorsSurveyors & PMs
One avoided mistake pays for the course.
Registering isn’t a commitment. You’ll get outlines, dates and pricing in writing, and you’ll be first to hear when new topics open.
Register your interest