How to use cavity wall ties correctly

20.04.2016
Blog Post
Image of wall with cavity wall ties

Incorrect use of cavity wall ties is one of the common problems found on site by our building control surveyors. The wrong choice of cavity wall tie, not enough ties, and wrong detailing around openings are frequently spotted.

The image above shows how not to do it; hooking wall ties together, using masonry chunks to retain the insulation and not maintaining the cavity width will all lead to cold bridging and dampness. There’s no surprise that this wall had to be demolished and rebuilt.

Here are some easy steps to get your wall ties right:

Table 5 of Approved Document A of the Building Regulations

  • You need two and a half wall ties per square metre of masonry. The maximum horizontal spacing is 900mm and the maximum vertical spacing is 450mm. That’s why cavity wall insulation boards usually have a maximum dimension on the short edge of 450mm.
  • Set each wall tie a minimum of 50mm into both masonry leaves.
  • Lay the wall ties to a slight ‘outward’ fall to prevent water passing to the inner leaf.
  • Only use insulation retaining clips that are compatible with your tie.
  • Change the wall tie pattern around openings such as windows, doors, roof verges and movement joints. Here the vertical spacing is reduced to a maximum 300mm and should be within 225mm of the opening. So realistically, that’s a wall tie every course of blocks within 225mm of the opening, which means you need to carefully cut (and clip) the insulation.
  • Cavity wall ties should be stainless steel.

Follow these simple rules and you’ll meet the Building Regulation requirements every time.

Further reading

Also read Avoid backfalling wall ties 

 

Please Note: Every care was taken to ensure the information was correct at the time of publication. Any written guidance provided does not replace the user’s professional judgement. It is the responsibility of the dutyholder or person carrying out the work to ensure compliance with relevant building regulations or applicable technical standards.

Comments

(No subject)

Submitted 3 years 9 months ago

What is the regulations on wall ties for dividing cavity walls between two properties,i.e acoustic reasons.

Reply

Submitted 3 years 9 months ago

Wall ties for separating walls between dwellings need to satisfy structural requirements as well as resistance to passage of sound. Width of the cavity will have a significant effect on both requirements. A wider cavity should benefit sound insulation performance but may affect the choice of wall ties.

The Approved Document to Part E recommends that wall ties for separating walls should be as described for ‘type A’. This relates to transmission of vibration. There is a need to ensure the choice of wall ties satisfies structural requirements suitable for the cavity width while being aware of the sound transmission properties. See AD E for description of type A wall ties.

Ultimately the wall must satisfy either the construction described for a licenced Robust Detail or be subject to a pre-completion test to demonstrate compliance.

Barry,

LABC Director of Technical Policy

Wall Ties

Submitted 3 years 1 month ago

hi, I know you shouldn't start wall ties in at DPC level but what is the reason for this?

In reply to by tim (not verified)

Reply to: Wall Ties

Submitted 3 years 1 month ago

Hi Tim, thanks for your enquiry.

The reason is to ensure adequate bonding between mortar and the course of brick above and below.

Kind regards,

Barry, LABC

76mm Cavity spacing

Submitted 2 years 11 months ago

What happened to the table which stated wall ties position change after cavity width increases beyond 76mm ie 750mm instead of 900mm?

Cheers

Reply to: 76mm Cavity spacing

Submitted 2 years 11 months ago

Hi, thanks for your question.

Having checked earlier versions of this article I'm afraid that we cannot find the table you're referring to.

Regards,

LABC

Wall ties on corners

Submitted 2 years 1 month ago

Hi there
I have been pulled up on site for not putting enough wall ties at internal and external corners. I am being told to put a tie every course either side of the corner. Is this correct?
Many thanks

Wall ties

Submitted 1 year 9 months ago

There is no need to install ties in on each course beside a corner. It is necessary to use them at each course at unbonded reveals.
[I believe that the British standard requires ties at 300mm centres at reveals.]

Wall ties on corners

Submitted 1 year 8 months ago

I agree with the first reply just a month ago, and furthermore LABC sketch E16MCPF5 Normal Corner detail is wrong as the ties are too close to the corner and could induce corner cracking due to moisture expansion of the brickwork. Ties should not be placed within 500mm of the external corner, and they are not needed any closer because in itself the wall return acts as a tie.

Remedial Wall Ties - Mid Terrace

Submitted 1 year 11 months ago

We are looking to buy a mid-terraced house. The survey has revealed cavity wall tie failure. The tell tale cracks are also visible on the adjacent properties.

Do you have any suggestions as to the approach I should take regarding the repair. I am concerned that if the properties on either side do not repair their walls I may still have a problem.

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