Butterfly Roof

1. Central Valley Leaks

• The valley carries a large volume of water
• If waterproofing fails, leaks develop quickly
• Blockages can make it worse

2. Ponding Water

• Water can sit in the valley if drainage is poor
• Leads to membrane wear and leaks

3. Membrane Wear & Cracking

• Flat or low-slope sections use membranes (EPDM, felt, GRP)
• UV exposure and weather cause brittleness and cracks

4. Drainage Blockages

• Leaves, moss, and debris collect in the centre
• Can block outlets leading to water buildup

5. Structural Stress

• Central load from water can cause sagging

6. Flashing Failure

• Weak points at valley edges and wall connections
• Leads to water ingress

7. Insulation & Condensation Issues

• Poor ventilation can cause condensation and damp

minor Repairs

• Clear debris from central valley
• Seal small cracks in membrane
• Fix minor flashing issues

moderate Repairs

• Replace sections of membrane
• Improve drainage outlets
• Reinforce valley waterproofing

major Repairs

• Replace full valley system
• Fix sagging or structural damage
• Upgrade insulation and waterproofing layers

When Replacement Is Needed

• Persistent leaks in valley
• Structural sagging
• Membrane failure across large areas
• Major renovation or modern build

Installation Steps

1. 1

   Remove Old Roof

   • Strip existing membrane and materials
2. 2

   Inspect Structure

   • Check rafters and central support
   • Replace damaged timber or supports
3. 3

   Form the Inward Slopes

   • Build two sloping sections toward centre
   • Ensure correct angle for drainage
4. 4

   Create Drainage System

   • Install central valley gutter
   • Fit outlets/downpipes for water removal
5. 5

   Add Layers

   • Vapour control layer
   • Insulation boards
   • Waterproof membrane
6. 6

   Apply Roof Covering

   • EPDM rubber
   • GRP fibreglass
   • High-performance felt
7. 7

   Finish Details

   • Flashing at edges and walls
   • Drainage fully tested
   • Gutters connected