PolyKey addresses many common problems with gaps in cavity wall insulation.


One of the main problems with gaps in cavity wall insulation is condensation on the un-insulated areas. This is because the insulation raises the overall internal temperature, thereby increasing the amount of moisture that the air is able to hold, while the areas missing insulation are cooler in cold weather, causing surface condensation and wet spots.

Technopol’s high-performance cavity wall insulation, PolyKey, addresses this and other challenges such as loose fill or fibrous insulation that allows water to penetrate to the inside, board insulation that shrinks and leaves un-insulated gaps, mortar droppings that fill the cavity and render it ineffective, as well as the corrosion of wall ties that can lead to the instability of cavity walls. The mortar key grooves with the top and bottom tongue and groove arrangements make PolyKey an extremely easy cavity filler to install.

Door and window openings
Openings for doors and windows are formed during construction to either fit frames as the work progresses, or into a pre-formed opening after the wall is built.

Frames built into the wall as work progresses
Timber frames that act as a profile for required openings are plumbed, squared and put in place before the brickwork begins. The PolyKey wall insulation elements are cut with a wood saw to fit around the frames where necessary. This method reduces the amount of plumbing and squaring required as the wall is built.

Securing frames in place
One way of securing frames is to use metal cramps that are fixed to the back of the frame and positioned to coincide with a horizontal joint. The cramps are laid on top of the bricks with the wall being built on top of it. Failure to ensure that the frame is plumb and level, may lead to problems when the reveals have to be plastered and the doors have to be fitted.

Pre-formed openings in cavity walls
To fit door and window frames in pre-formed openings, a type of fixing that consists of a plastic sleeve which encases a toughened zinc screw is often used. When the screw is tightened, the sleeve expands, securing the frame in place. Once the frame has been fixed in place, the outside and inner edges can be sealed with waterproof mastic which will make the frame completely watertight.

Jambs (sides of openings)
In cavity walls, the reveals (face of the opening) can be constructed either square or rebated. The cavity can be closed at the opening by using a suitable frame or by returning the inner leaf towards the outer leaf. When the inner leaf abuts the outer leaf, a vertical DPC must be inserted to prevent moisture from passing through and it should extend into the cavity to avoid mortar from bridging. When 100mm blocks are used, the DPC must be 150mm.

The function of the sill is to shed rainwater from the window frame and away from the wall below. If the sill is small, a cavity closer block is bedded below the inner window board to provide a larger, more solid base onto which to fix the window board. This must be insulated from the external face.

Furthermore, it is also recommended that the foundation wall includes PolyKey as perimeter insulation.

Technopol (SA)
Tel: 011 363 2780
Website: www.tehnopol.co.za