BS Fixings

Cavity Screw Ties: How to Achieve Professional Results

Cavity screw ties are an essential component of cavity wall systems, forming external and internal leaves to single-skin buildings. When used correctly, they ensure that both walls on either side of the cavity function as a single unit. The incorrect installation of cavity screw ties is a common problem in construction: here we look at some of the issues incorrect installation can cause and offer some professional advice on avoiding them.

The most common mistakes when installing cavity screw ties, all of which can lead to damp, cold bridging or total system failure are:

  • Using the wrong type of tie
  • Using an insufficient amount of ties
  • Hooking ties together
  • Using pieces of masonry to retain insulation
  • Not maintaining the correct cavity width
  • Improper spacing

Correctly installing cavity screw ties begins with selecting a quality product, such as the ties produced by our trusted partner company Bluebird Fixings.  Here is some advice on correct installation:

  • Ascertain the appropriate screw tie length with Table 5 of Approved Document A of the Building Regulations
  • 2.5 screw ties will be needed for each square metre of masonry
  • Maximum vertical spacing is 450mm and maximum horizontal spacing is 900mm
  • Set each tie into both masonry leaves at a minimum of 50mm
  • Install ties with a slight outward fall to prevent transference of moisture to inner leaves
  • Wall tie pattern should be changed around openings and ties installed within 225mm of each opening
  • Use only compatible plugs and insulation retaining clips

For more information about Bluebird Fixings cavity screw ties, check the product page and this week's news article. Do not hesitate to contact our technical team for further advice.

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