Cavity Wall

The Technical stuff…Why Cavity wall

THEN – pre wall ties

Originally in England most brick buildings were constructed using single skin walls. The bricks were laid in alternating directions to resist movement in all directions. These walls while remain structurally sound are not very well suited to repelling moisture from the outside. Also the mortar between the bricks can conduct moisture and will and does lead to penetration damp problems.

Modern Cavity Wall construction - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.
Solid Brick Wall

NOW – with wall ties

Cavity Walls…. Dry plaster since WWII
Cavity walls were first used in the early 19th century, however they only became after the 1920’s basically post World War II England. Walls were now useful for stopping damp as they comprised of two skins with a gap between (around 10cm). As these now ‘cavity’ walls have no contact between the inner and outer leaf this means no access for damp also.

Modern Cavity Wall construction - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.
Cavity Brick Wall

And now …….the wall ties

The inner and outer leaf of the cavity walls require a link to hold the two together to stop the ‘bowing’ or the walls or wall movement. Cavity walls are held together with metal restraints or ties to enable a link (for strength) to be retained while at the same time leaving a cavity to prevent possible damp.

The two original types of mild steel wall ties (plastic was initially tried and rejected).

Fishtail Wall Ties (1920 - 1950) - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.
Fishtail Wall Ties (1920 – 1950)
Butterfly Wall Ties (1964 - 1981) - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.
Butterfly Wall Ties (1964 – 1981)

Modern remedial wall tie below– used to replace the above wall ties.

Modern Remedial wall tie - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.

Modern cavity remedial wall ties are composed of corrosion resistant Stainless Steel tie bars with Neoprene sleeves. The tie features a unique ‘tall-nut’ which once tightened, forces the inner leaf Neoprene sleeve to open and grip in the masonry.

Why do wall ties fail in cavity walls?

Cavity wall ties are prone to rust if not properly protected, moisture can filter its way
along the metal causing oxidation of the original wall tie.

Cavity wall ties are prone to rust. - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.

Properties which tend to have the worst failed wall ties were build with the mild-steel ‘fishtail’ ties (1920 –1950) and butterfly (1964-1981) Fishtail ties can be particularly bad on occasion forcing the bricks apart as they corrode away.

The signs . . .

  • Expansion of the metal wall tie can cause brickwork to crack both horizontal and vertically
  • Cracking left unattended can result in destabilization of the wall
  • Cavity wall ties are prone to rust if not properly protected, moisture can filter its way along the metal causing oxidation.
Horizontal Crack is a sign of failing wall ties - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.
Horizontal Crack
Stepped Crack is a sign of failing wall ties - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.
Step Crack

Bowing Wall is a sign of failing wall ties - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.
Wall Bowing

Brick pillar movement is a sign of failing wall ties - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields.
Brick pillar movement

How we fix cracks and failed wall ties ……

This is Rem Tie at work….

Wall Tie Replacement - walls marked off  - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Lets get the walls marked off
Wall Tie Replacement - walls marked off - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Current wall ties marked off
Wall Tie Replacement - walls drilled - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
….and drilled

Wall Tie Replacement - walls ties in position - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Ties in position ready to go in ….
Wall Tie Replacement - walls ties in position - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Ties in position ready to go in ….

Wall Tie Replacement - walls ties inserted on torque settings - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
New mechanical-mechanical ties inserted on torque setting…..

Wall Tie Replacement - cut out old ties via the mortar - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
New Wall Ties now in …. Now start cutting old ties out via the mortar

Wall Tie Replacement - Cutting out the corrosion to old tie - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Cutting out the corrosion to old tie now to isolate with foam….
Wall Tie Replacement - insert foam - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Foam going in

Wall Tie Replacement - plug holes with colour match cement - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Plugging holes and pointing slots ….. Colour match cement going in…

Possible Extra – Crack Stitching

If there is a step in the cracked wall, this will need a horizontal inserted resin bonded Helifix bar as well as wall ties either side of the step crack.

Crack Stiching using resin bonded helifix bars - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Bars In

Crack Stiching using resin bonded helifix bars - Rem-tie Ltd in North East, Newcastle, Durham, Sunderland, North Shields
Wall isn’t going anywhere

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