Timber and Steel Frame Construction And Insulation – Sitework

Timber Frame Insulation

Between the timber studs

  1. The product should be cut to fit tightly between the timber studding and positioned against the inner face of the sheathing board. Any gaps along the edges should be filled with expanding polyurethane insulation foam. The insulation board should be held tightly in place by timber battens to the warm side of the insulation.
  2. The cavity created by the space between the product and the dry lining can be utilised as an insulated service void.
  3. A sealed polyethylene VCL with a minimum thickness of 0.125 mm (500 gauge) with lapped and sealed joints is placed over the timber stud face before applying the internal finish.

Dry Lining

  1. The Ballytherm BTDL Dry Lining Boards should be butted tightly against each other over the timber studs in order to prevent gaps. To satisfy the requirements of NHBC Standards, a VCL should be placed on the warm side of the wall insulation system. Any service penetrations should be tightly sealed with expanding polyurethane foam, flexible sealant or other proprietary product.
  2. The insulated dry lining boards are secured with conventional nails or drywall screws at nominal 150 mm centres, and finished in accordance with conventional good practice.


  1. The insulation boards should be installed on the outside of any timber sheathing board, closely butted with joints staggered and restrained using galvanized clout nails or screws at 300 mm centres around the board perimeters, and at 400 mm centres for intermediate timbers within the board area.
  2. It is essential that the nails or screws locate the timber studs and not just the timber sheathing board.
  3. The use of self-adhesive foil-tape over the joints, between the insulation boards, is not recommended.
  4. Wall ties securing the external masonry leaf are fixed through the insulation board and timber sheathing board into the timber studs, whilst the insulation is retained in position by the plastic retaining-discs on the wall ties.

Points to watch

  • Seal around services to reduce air leakage.


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 info@ballytherm.ie or use our contact form.


Design Guidance