Celotex GA4000 Insulation Board Installation Tips

Celotex GA4000 Insulation Board Installation Tips

Celotex GA4000 insulation boards, focusing on measurements, cutting, fixing, and sealing:

Measuring and Cutting

  1. Flat Roofs (Below Timber Joists):
    • Measure the space between joists precisely.
    • Cut the board to fit snugly, leaving a 10mm gap around the perimeter for expansion.
  2. Flat Roofs (Between Timber Joists):
    • Measure joist spacing and subtract 2-3mm for a friction fit.
    • Use a straight edge and a fine-toothed saw or a sharp utility knife for cutting.
  3. Pitched Roofs (Between Timber Rafters):
    • Measure the gap between rafters. Cut the insulation board 1-2mm smaller for a tight fit.
    • For angled cuts, use an angle finder and mark the board before cutting.


  1. Flat Roofs (Below Timber Joists):
    • Use appropriate screws and washers, spaced at 300-400mm intervals.
    • Ensure the fixings are long enough to penetrate both the insulation board and into the joist by at least 25mm.
  2. Pitched Roofs (Below Timber Rafters):
    • If mechanically fixing, use fixings that are suitable for the depth of the insulation and the rafter.
    • Space the fixings at 600mm centers along the rafters.
  3. Wall Applications (Solid Masonry Internal Linings):
    • Use a combination of adhesive and mechanical fixings.
    • Adhesive should be applied in continuous beads approximately 300mm apart.


  1. All Roof and Wall Applications:
    • Use airtight tape specifically designed for insulation boards to seal all joints.
    • Ensure all cuts are clean and straight for effective sealing.
  2. Vapor Barriers:
    • Overlap vapor barrier sheets by at least 100mm.
    • Seal overlaps with vapor barrier tape.
  3. Around Penetrations:
    • Use expanding foam or sealant for gaps around pipes, cables, or other penetrations.
    • Ensure the foam or sealant is compatible with the insulation material.

Additional Tips

  • Accuracy: Always double-check measurements before cutting. A slight error in measurement can lead to gaps and reduced insulation efficiency.
  • Cutting Surface: Use a stable and flat surface for cutting. A workbench with a cutting mat is ideal.
  • Tools: Keep your cutting tools sharp. Blunt tools can lead to uneven edges, making it harder to seal joints effectively.
  • Handling: Handle the boards with care. Despite their rigidity, the edges can be prone to damage if mishandled.
  • Clean Work Area: Keep your work area clean. Debris and dust can hinder proper adhesion of tapes and sealants.