Insulation Below A Groundbearing Slab – Sitework

Insulating below a groundbearing slab

Installation sequence
  1. Blind the hardcore with sand to give a smooth surface.
  2. Install the DPM / Radon barrier.
  3. Cut Ballytherm boards to height and fit vertically around the perimeter of the floor.
  4. Lay boards across the floor surface in broken bond. Butt boards tightly together and cut to fit neatly at edges and around penetrations.
  5. Lay VCL: lap and seal all joints.
  6. Pour and tamp slab.
  7. Pour screed.
Points to watch
  • Test any embedded services before pouring the slab,
  • Protect Ballytherm boards from damage while the slab and screed are being poured: use barrow boards.
  • Protect the exposed edge of the Ballytherm boards when levelling the slab.
  • Cut boards to fit tightly together.

Further Advice & Information

For more information about Ballytherm products, technical advice, or guidance on the suitability of our products for your project, contact us at + 353 (0)49 95 27000,, email us at or use our contact form.

Floor Insulation


Design Guidance