Partial Fill Cavity Wall Insulation – Sitework

Insulating partial fill cavity walls

Installation sequence

  1. Raise the inner leaf 450mm above the outer leaf (two courses of blockwork or six of brickwork).
  2. Fit the first run of Ballytherm boards against the inner leaf, supported on top of wall ties or the concrete cavity fill.
  3. Raise outer leaf by 450mm.
  4. Notch the top of the Ballytherm boards and fit wall ties.
  5. Fit clips to hold the boards against the inner leaf.
  6. Repeat the sequence to the required height of the wall, staggering the vertical board joints.

Points to watch

  • Ensure wall ties slope down from the inner leaf to outer leaf to prevent water travelling to the inner leaf.
  • Use a cavity board across the top of the insulation to prevent mortar building up on the insulation or bridging the cavity.
  • Fit Ballytherm neatly to elements, which bridge the cavity such as door and window sub-frames, lintels and cavity closers.

Floor Insulation


Design Guidance

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.