How to install an IsoBoard ceiling

Tired of an ugly old ceiling or keen on the look of exposed trusses? IsoBoard has the ideal solution – and provides superb insulation!

You will need


  • appropriate standard lengths of IsoBoard
  • concealed ceiling clips (included with IsoBoard)
  • adhesive
  • cornicing
  • small wood screws to secure ceiling clips (10-15mm)
  • longer wood/drywall screws to secure IsoBoard on the perimeters where screws will be covered by cornicing (length of screw depends on thickness of IsoBoard selected; approximate length of screw should be IsoBoard thickness plus 15mm.)


  • tape measure
  • pencil
  • battery-powered drill/screwdriver
  • skeleton gun or spatula
  • utility knife
  • straight edge to guide knife while cutting

How to install the IsoBoard

Preparation is, as always, the secret to success!

Before you start Choose the direction in which the boards must run and select the appropriate standard length to minimise waste (standard lengths range from 2 400mm to 8000mm). Select IsoBoard thickness according to your requirements: thicker boards provide more thermal resistance; 30mm or 40mm thickness is preferred in ceilings.

Install brandering support for IsoBoard: maximum spacing is 750mm; 600mm is ideal indoors and you should use 400mm spacing outdoors and in high wind areas. There should be a perimeter brandering all along each wall to positively secure the board on both ends.

1. Cut to size The board is readily cut with a sharp utility knife; always use a straight edge to keep the blade running true. Cut the board and position it to confirm that it fits before applying adhesive.

2. Apply adhesive Use 5ml blobs (about a teaspoonful) at 200mm intervals along the brandering. Don’t smear the adhesive flat like butter; it must make contact with the brandering and IsoBoard. The adhesive is the permanent bond that keeps the IsoBoard in position.

3. Fit the board Push the first board up into the adhesive.

4. Insert perimeter screws Secure the board along the perimeter with long drywall screws.

5. Insert concealed clips Secure the board to central brandering with concealed ceiling clips and small wood screws.

6. Repeat Measure, cut, fit and install subsequent boards, fitting them together using the tongue and groove along each length.

7. Cut and fit last board Secure with perimeter screws.

How to install the cornices

1. Mark guidelines Use a pencil to mark where the cornices will intersect in order to cut the correct angles.

2. Measure and cut cornicing to required length.

3. Mark and cut angles Use a mitre-cut guide to cut the angles cleanly.

4. Apply adhesive and fit Apply a bead of adhesive to both edges, as well as the joint between the cornice pieces. Fit the boards into place.

5. Smooth and fill joints Smooth then remove excess adhesive using a damp sponge. Repair minor damage using Painters Mate or something similar.

To finish Paint the board with two coats of water-based paint or wood stain.

Project notes
  • Always use adhesive!
  • Always fix IsoBoard lengths positively to perimeter brandering on both ends.
  • Avoid butt joints: ensure the board runs from wall to wall.
  • Do not try to fill joints with plaster to create a skimmed ceiling look. Order the board with a bevelled edge or Isopine finish.

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April 2023

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