Cavity walls have replaced solid walls because they are more resistant to rain penetration.
- The clean air space after the cavity boards have been fixed in place is not normally less than 50mm wide occasionally in sheltered areas a 25mm air space is specified .
- Make sure the ties are facing the right way up with the drip positioned in the center of the cavity and also facing down. (see drawing no1)
- When attaching insulation boards make sure they are put in half bond and attached with plastic clips called buttons. (see drawing no2)
- As you take the blockwork up put a piece of wood or some blocks on the outside to protect the cavity and face work from any mortar droppings (see drawing no3).
- Store insulation away from rain.
- Clean of any mortar from the outside skin of blockwork.
- On the d.p.c. course remove every 5 brick this will enable you to remove all mortar droppings that have built up on the cavity tray they can be put back when the wall is completed.
- Support with at least 2 ties at the top and 2 at the bottom of every cavity insulation board.
- Use a minimum of 3 ties per meter sq
- Ties usually start at d.p.c. every 900mm long and every 450mm high staggered every course used so they are not all in line and give the wall extra strength ties are used every 225mm high on all openings and corners also to give extra strength
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