Cavity Walls

Construct Cavity Walling

Student Copy

Name ………………………………...

What is a cavity wall?

A cavity wall is made up from:

•

•

•

Cavity wall construction

50mm minimum width of air gap

Section through a cavity wall

Solid Walls can let dampness into buildings.

Section through a solid wall

Why do we use cavity walling?

Cavity Walls were

originally

introduced to

prevent ________

penetration.Section through a cavity wall

Problems?• Weakness: Two slender half brick / block skins

are not as _______ as a one brick thick solid

wall. How can this Kind of walling be strengthened?

The use of ______ ______ Ties

_______ ______ TiesThe walls are supported and tied into one another by means of specially designed metal ties called ‘_______ ties’.

Wall Ties are made from __________ steel

Cavity Wall TiesProblems can occur when bridging the cavity, such as

_______ penetrating from the outer leaf to the inner leaf.

Section through a cavity wall

Common Faults

Wall tie spacing’sBuilding Regs state wall ties must be positioned _____mm vertical ______mm horizontal (100mm cavity) and no more than 300mm vertically on un-bonded reveals.

Bridging the cavity can create problems.

Preventing ______ Transfer.

The ______ DPC prevents water crossing along the top of the air-brick liner.

Section through a cavity wall

Typical components needed for bridging cavities at openings.

Keep the cavity clean.Mortar droppings can

gather on wall ties and at

the bottom of the cavity

creating a ________ for

water to pass through to

the inner leaf.

Section through a cavity wall

Clean Cavities

Keep the cavity

clean to

prevent ______

penetration

Section through a cavity wall

Ensuring Cleanliness• _______ Hole

Ensuring Cleanliness• _________ _________

Wall construction below ground level

Cavity walling below ground level:-

• Cavity wall formed with two leafs of

common bricks. The external leaf will revert

to facing bricks __ course below ground level

to allow the bricklayer to ensure that bond is

worked out

Broken BondIf Broken Bond can not be avoided the piece should be

placed in the centre of the wall, or against the reveal.

No cut should be less than __ _______

If bastard sized window and doors are used then the

piece is better placed _________ the opening if possible.ANY CUT SHOULD ALWAYS STAY IN THE SAME

POSITION