Bonded Bead
For The Future


“Bonded Bead”
 Within the cavity wall
(full fill every time)


List of faults within photo “Typical Badly Installed Cavity Boards”

  • Problem 1: THERMAL BRIDGING:

Gaps left between straight edged insulation boards, allows air circulation and therefore severe heat loss.

  • Problem 2: THERMAL LOOPING:

The air gap between insulation boards and the inner leaf allow air circulation, thus expelling warm air from the inner leaf. This gap is a result of material and other debris falling between the insulation and the inner leaf.


  •   3mm gap between sheets causes U-Value loss of 158% of calculated value.
  • 10mm gap between sheets causes U-Value loss of 193% of calculated value.

“Typical Badly Installed Cavity Boards”



Bonded Bead Cavity Wall Insulation is installed using approved equipment marked with the appropriate IAB Certificate number.

Where a semi-detached or terraced property is to be treated, the insulation is contained by inserting a cavity barrier at the line dividing the properties. This consists of a continious inflatable sleeve or a nylon brush. After filling the cavity barrier is retained in the cavity and the drill holes filled.

After completion of the cavity assessment and drilling plan for the building, preparation for injection into the cavity is as follows:
Holes of 22mm diameter are drilled in the outer or inner leaf. They are normally spaced not more than 0.6m horizontally apart and the top row of holes in each wall is not more than 200mm from the top of the wall. A similar series of holes is drilled below windows and obstructions and if found to be necessary, along the lines of the roof slope at gable ends. A further series of holes 2.0m apart is drilled at the middle height of a two storey building to ensure complete fill of the cavity space.

Bonded bead with the correct rate of binding agent, is injected into the cavity through a flexible pipe fitted with a non-directional nozzle. The material packs to a uniform density in the cavity and this is not effected by the injection equipment. Holes beneath ground floor windows are injected first and filling then continues upwards until a complete fill has been achieved.

After injection the wall is made good to match the existing finish as closely as possible. All the air vents are checked. In all cases flues are carefully checked on completion by means of an appropriate test to ensure they are not obstructed by the insulant.
Any insulant that has not been blown through the top of the cavity into the loft space is removed and any points of leakage sealed.

A typical Bonded Bead Hole Drilling pattern in a Detached house is shown below


Meeting .27U Value in a Standard Cavity Wall