This document discusses cavity wall construction. It describes how to maintain a clean cavity, properly bed wall ties, and treat openings. Four types of wall ties are shown. Cavity walls are more rain resistant and better insulated than single skins, but require good design and workmanship. Ties should be spaced regularly and bedded firmly in mortar at least 50mm into each leaf. The cavity must be kept clear of mortar droppings to prevent deterioration of the ties.

1. CAVITY WALLINGCAVITY WALLING
OBJECTIVESOBJECTIVES
 EXPLAIN HOW TO MAINTAIN A CLEAN CAVITY
 DESCRIBE WITH THE AID OF A SKETCH GOOD BEDDING
PRACTICE FOR WALL TIES
 COMPARE THE TYPES OF MATERIALS USED
UNDERGROUND
 DESCRIBE HOW TO TREAT AT CILLS AND OPENINGS
 SKETCH FOUR TYPES OF WALL TIE

2. CAVITY WALLSCAVITY WALLS
 MORE RAIN RESISTANT
 BETTER INSULATED
 DEPENDENT ON GOOD
DESIGN AND
WORKMANSHIP

3. CAVITY WALLINGCAVITY WALLING
 STANDARD FORM OF EXTERNAL WALLING USED IN
CONSTRUCTION
 TWO SKINS OF WALLING USUALLY 102mm BRICK
EXTERIOR AND 100/125/150 LIGHTWEIGHT BLOCK
INTERNAL
 MINIMUM OF 50mm CAVITY TO BE MAINTAINED
THROUGHOUT CONSTRUCTION
 SKINS JOINED TOGETHER USING NON-CORROSIVE
TIE WIRES FOR STABILITY

4. CAVITY WALLINGCAVITY WALLING
Internal Blockwork
Damp Proof Membrane
Oversite Concrete
Rain penetrates the
outer leaf but is
unable to bridge the
cavity

5. TIE WIRES IN CAVITY WALLSTIE WIRES IN CAVITY WALLS
WIND
LOAD
SINGLE
LEAVES
EFFECTIVELY
TIED
LEAVES
DEFLECT
UNDER
LOAD

6. COMMON TIES USED IN CAVITYCOMMON TIES USED IN CAVITY
WALLINGWALLING

7. CAVITY WALL TIESCAVITY WALL TIES

8. CAVITY WALL PROBLEMSCAVITY WALL PROBLEMS
excessive mortar
droppings in cavity
and building up on
wall ties
Deteriorated fish tail wall ties.

9. GOOD PRACTICE FOR PLACING TIESGOOD PRACTICE FOR PLACING TIES
ENSURE THAT TIES
ARE FIRMLY BEDDED
INTO THE BED JOINTS
AT LEAST 50 mm

10. NEVER SLOPE TIES TO INNER
LEAF
KEEP TIES HORIZONTAL OR IF UNAVOIDABLE
SLOPE TO OUTER LEAF

12. MAIN POINTS TO CONSIDERMAIN POINTS TO CONSIDER
 ONLY USE SPECIFIED TIES
 PRESS FIRMLY INTO MORTAR BED
 BED TIES AT LEAST 50mm INTO EACH LEAF
 ENSURE DRIP IS IN CENTRE OF CAVITY
 NEVER INCLINE TIES TOWARDS INNER LEAF
 EXTRA TIES ARE REQUIRED AT JAMBS OF OPENINGS AND UP RAKES
AT GABLES
 NEVER BEND TIES TO SUIT VARIATION IN GAUGE
 KEEP TIES CLEAR OF MORTAR DROPPINGS
 TIES SPACED 900mm HORIZONTALLY AND 450mm VERTICALLY

13. MAINTAINING A CLEAN CAVITYMAINTAINING A CLEAN CAVITY
CLEAN EXCESS
MORTAR OFF
WHEN
BUILDING
AVOID ROUGH
EDGES INTO
CAVITY
ABOVE D.P.C.
TRAYS
WEEPHOLES AT
900mm CENTRES
CAVITY
BATTEN
KEEP CAVITY
TRAYS AND
TIES CLEAR
OF MORTAR

14. CAVITY WALLS BELOW GROUNDCAVITY WALLS BELOW GROUND
CONCRETE STRIP
FOUNDATION
HORIZONTAL D.P.C. MIN.
150mm ABOVE G.L.
LEAN MIX CONCRETE TO
RESIST LATERAL
PRESSURE
OPENINGS FOR
SERVICE
DUCTS
SPANNED BY
LINTEL
FACEWORK SET OUT
BELOW GROUND
LEVEL

15. CAVITY WALLING FORMED BY USE OFCAVITY WALLING FORMED BY USE OF
FOUNDATION BLOCKFOUNDATION BLOCK
1 METRE
G.L.
SECTION THROUGH CAVITY WALL

16. CAVITY WALL FORMED BY USING SOLIDCAVITY WALL FORMED BY USING SOLID
FOUNDATION BLOCKFOUNDATION BLOCK
G.L.
SOLID FOUNDATION
BLOCKS ARE AVAILABLE
AS LIGHTWEIGHT
BLOCKS. THEY CAN BE
HANDLED BY ONE PERSON
THEY ARE ALSO
AVAILABLE IN HEAVY
CONCRETE. THESE
SHOULD BE LIFTED BY
TWO PERSONS TO AVOID
INJURY

17. CAVITY DETAIL AT CILL AND OPENINGCAVITY DETAIL AT CILL AND OPENING

18. ALTERNATE METHOD OF CLOSING CAVITYALTERNATE METHOD OF CLOSING CAVITY
AT REVEALSAT REVEALS
BLOCKWORK
RETURNED TO
OUTER BRICK
LEAF
D.P.C. PLACED
AS A BARRIER
TO RAIN
PENETRATION

19. CAVITY CLOSERCAVITY CLOSER
CAVITY CLOSER
ALLOWS OPENINGS TO
BE QUICKLY AND
EFFECTIVELY CLOSED

20. CAVITIES BELOW GROUND (3)CAVITIES BELOW GROUND (3)
D.P.C. MIN
150mm
ABOVE G.L.
Brick