Wij gebruiken cookies om uw ervaring te verbeteren. U kunt kiezen welke cookies u accepteert.
Engineered Timber · For Builders
I-joist specification combines flange and web parameters that don't exist for solid timber joists. This template covers the complete specification clause including notching limits and required acoustic detailing.
Free Download
NBS-format clause, common errors checklist, and standards reference. Editable PDF format ready for your tender documents.
We respect your privacy. No marketing email — only project-related technical updates if you opt in later.
Specification Checklist
241, 302, 356, 406mm typical. Deeper = longer span / greater stiffness.
LVL or solid timber. LVL flanges allow longer spans.
OSB/3 or hardboard. Affects shear strength and notching capacity.
Manufacturer's certified span table for actual section.
400 or 600mm centres typically.
Minimum 45mm at supports, with bearing stiffeners for end loads.
Knockout points only. No site notching outside designated zones.
Solid blocking at supports, lateral restraint mid-span on long spans.
Example Clause (NBS Format)
ENGINEERED I-JOISTS Specification: - Manufacturer: BBA-certified European producer - Section: 302mm depth × 89mm flange - Flange material: Laminated Veneer Lumber (LVL), grade per BBA certificate - Web material: 9mm OSB/3 to EN 300 - Spacing: 400mm centres - Bearing: 45mm minimum, with 2-ply bearing stiffeners at all end supports - Strapping: Solid blocking at supports and mid-span (spans over 5m) Web penetrations: - Round services penetrations: Manufacturer's knockout points only - Maximum hole size: Per manufacturer's hole chart - No site cutting of web outside designated zones Span verification: Per manufacturer's certified span table for floor loading 1.5 kN/m² (residential) or 4.0 kN/m² (commercial) Acoustic detailing (separating floors): Resilient bars to ceiling, 50mm mineral wool between joists, floating screed on resilient layer Certification: BBA Agrément Certificate or equivalent third-party certification
Copy and paste this clause into your tender. Adjust dimensions, grades, and project-specific requirements.
Common Errors
Site cutting i-joist webs
Correction: I-joist webs are designed for shear via continuous OSB/plywood. Cutting outside designated knockout zones removes structural integrity.
Insufficient bearing length
Correction: 45mm minimum at all supports. End bearings need stiffeners (2-ply web reinforcement) to prevent web crushing.
No fire stops at penetrations
Correction: Services penetrations through compartment floors need intumescent collars or pillows around services.
Wrong span table used
Correction: Always use manufacturer's certified span table for actual section. Don't interpolate or use generic tables.
Reference Standards
Frequently Asked
I-joists for spans over 4.5m, deep services zones, or where weight reduction matters. Solid timber for short spans, simple framing, and budget projects.
LVL flanges are standard for premium i-joists, allowing longer spans and higher loads. Some manufacturers offer solid timber flanges as a budget option for shorter spans.
Only at manufacturer's designated knockout points. Web cutting outside these zones removes shear capacity. For complex services, use the manufacturer's services penetration calculator.
Need a tailored quote?
Our technical team supplies certified, traceable timber matching this specification. Quote within one business hour.
Request Quote