Roof Battening

Category: Battens & Underlay
Tags: roof battens, batten spacing, roofing basics, slate roofing, tile roofing

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What You’ll Learn

This guide explains everything you need to install roof battens correctly, including:

• What battens are and what they do
• The correct batten sizes and grades
• How to measure and mark batten spacing
• Tools you’ll need
• Step-by-step instructions
• Common mistakes to avoid
• Professional roofer tips
• FAQ

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What Are Roof Battens?

Roof battens are horizontal timber strips fixed to rafters. They:

• Support roof tiles or slates
• Keep rows straight and evenly spaced
• Provide fixing points for tiles/slates
• Strengthen and stabilise the roof structure

In the UK, the most common sizes are:

• 25×38mm (standard tile battens)
• 25×50mm (heavy-duty or windy areas)

Battens must be graded timber, stamped with BS5534.

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Tools You’ll Need

Basic Tools

• Tape measure
• Roofing square
• Chalk line / string line
• Pencil or marker
• Hammer or nail gun
• Spirit level

Optional

• Laser line
• Batten gauge
• Clout nails or ring shank nails
• PPE: gloves, boots, eye protection

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How to Calculate Batten Spacing

Batten spacing depends on the type of roofing material.

For tiles (concrete or clay):

1. Check the tile manufacturer’s spec
2. Find:
   • Headlap
   • Gauge
3. Measure two tiles together and confirm the working gauge
4. Typical tile gauge: 75–345mm depending on tile type

For natural slate:

Use standard gauges:

• 500×250 slate → 100mm headlap → gauge ~ 250mm
• 400×250 slate → 90mm headlap → gauge ~ 200mm

Rule: the smaller the slate, the smaller the gauge.

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Step-by-Step: How to Lay Roof Battens

1. Fit Your Underlay First

• Lay felt/underlay horizontally
• Overlap the layers by 100–150mm
• Nail at rafters, not between them
• Keep it smooth, no sagging

2. Mark Your Gauge

You need two key lines:Eaves batten position

• Measure up from fascia
• Allow for tile overhang
• Mark a straight line with a chalk line
• Gauge marks up the roof
• Use your tape and square
• Mark every gauge up both rafter sides
• Snap chalk lines across for accuracy

Start Fixing Battens

• Use graded BS5534 stamped battens
• Lay them across rafters, follow your chalk lines
• Nail with 2 nails per crossing
• Keep battens dead level

Keep Your Lines Straight

• Use a string line across each row
• Adjust battens if they drift
• Check your gauge regularly
• Don’t trust just your eye — small errors grow fast

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Common Mistakes to Avoid

🚫 Not using graded timber — this fails building control
🚫 Wrong gauge — tiles won’t sit correctly
🚫 Running battens uphill/downhill
🚫 Too few nails
🚫 Battens touching the felt (should be above)
🚫 Not leaving room for ventilation at ridge/eaves

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Pro Roofer Tips

Use a batten gauge tool — it speeds up spacing dramatically
Pre-mark all gauges before nailing anything
Keep battens 5mm apart where they join (expansion gap)
If a rafter dips or rises, pack battens to keep lines straight
Always check manufacturer gauge for tiles — don’t guess
For slate, use slate gauges + consistent head lap

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FAQ

What size battens should I use?

For most roofing: 25×38mm.
For high wind zones: 25×50mm.

Can I use ungraded timber?

No. Building regulations require BS5534 graded battens.

How do I stop battens from twisting?

Store them flat and fix them quickly. Keep battens spaced 5mm at joints.

How do I check my gauge?

Measure 2 tiles together on the ground → find working gauge → transfer up the roof.