Products & Applications

Partial Cavity Wall Insulation

A partial fill cavity wall application provides the most effective barrier to rain penetration and allows traditional cavities to be achieved without increasing the overall wall thickness. The insulation is fixed to the inner leaf of the wall construction, maintaining a clear cavity which avoids the problems associated with full cavity fill. For this application we would recommend the use of Seconds high performance rigid urethane insulation.

Fixing details

Determine the overall cavity width by adding the thickness of insulation required to the residual cavity width (25mm up to 12m in height subject to confirmation from Local Authority Building Control).
Install the first row of wall tiles at 600mm centres to the inner leaf, one course of blockwork below the d.p.c.
Wall ties should include a retaining disk/clip and be of double drip type, installed drip downward.
Continue constructing the inner leaf up to the next wall tie course at 450mm. Position wall ties at the usual 900mm centres for subsequent courses.
The first row of boards should now be installed, ensuring each board is retained tight against the inner leaf at three points (this includes cut boards at details, see fig. 3).
Continue installing wall ties and boards as work proceeds, taking care to remove excess mortar and protecting the board edges from mortar snots by using a cavity board (see fig. 2).
Always ensure accurate trimming to achieve close butting joints and continuity of insulation.
A vertical damp proof course should be installed at window and door openings. The insulation boards can be used to prevent a cold bridge at details (see fig. 4).
When insulating to ceiling height at a gable, wall boards should be continued 450mm beyond the ceiling and a cavity tray installed above the insulation.
Boards should be cut using a sharp knife or a fine toothed saw.