MASONRY WALL TIES

Wall ties, often titled ’unseen brick ties’ are used to tie the internal and external leaves of a cavity wall together, allowing those parts to act as a corresponding element. In fact, they provide structural stability by ensuring both leaves work together to provide strength and resist loading. They are also hidden from view after construction. Wall tie was introduced to northern Europe in the late 19th Century and began to become more widespread in the 1920s. The ties are added to the cavity wall during construction, with the ends of the ties bedded into the mortar bed at regular intervals. They are also designed to accommodate small movements from temperature fluctuations and prevent outside water transfer. Ties must be long enough to span the cavity and provide the minimum embedment in the mortar at both ends, typically 62-75mm. For example, a 200mm long wall tie is suitable for cavities from 50-75mm. Standard wall ties are available to suit cavity widths from 50mm to 450mm. The minimum quantity of cavity wall ties (as defined in Eurocode 6) is 2.5 ties per square metre. Typically they are installed at 900mm horizontal x 450mm vertical spacing and should be staggered across the wall area to provide an even distribution. Additional ties should be used at a rate of one per 300mm height around openings and unbonded edges (although blockwork coursing usually means that they are installed at 225mm vertical spacing). Choosing the correct wall tie and spacing for a specific application is critical to the structural integrity of a cavity wall and the manufacturer’s advice should be sought.

Their selection and spacing is determined by a number of design factors, including:

· Building type and height
· Geographical location
· Cavity width
· Type of masonry used.

TYPES OF WALL TIES

The construction and properties of ties vary depending on the application, but they are categorised into four basic types to suit different masonry applications and loads:
• Type 1 (Heavy-Duty Applications) – suitable for most building types and sizes, but not very flexible. Type 1 ties made from steel are relatively substantial and may result in moderate thermal bridging i.e. heat loss.
• Type 2 (General-Purpose Applications) – suitable for domestic dwellings and small commercial buildings on flat sites with wind speeds up to 31m/s, making them suitable for all UK regions. Type 2 wall ties are suitable for buildings up to 15m in height.
• Type 3 (Basic Applications) – suitable for domestic dwellings and small commercial buildings on sites where the basic wind velocity is 27m/s or less, making them unsuitable for parts of northern Scotland and Ireland.
• Type 4 (Light Duty) – suitable for domestic dwellings of box-form construction with leaves of similar thickness, on sites where the basic wind velocity is 27m/s or less, making them unsuitable for parts of northern Scotland and Ireland.

Heavy-Duty Steel Tie

A substantial Type 1 tie used in the construction of all building types and heights, anywhere in the British Isles. They are suitable for partial and full-fill cavities, generally up to 225mm.

Wire Wall Ties

Stainless steel wire ties are the cheapest and most widely used option for cavities up to 150mm. They are typically produced as Type 2 and 4.

Basalt-fibre Wall Ties

A range of very low thermal conductivity ties made using basalt fibres is available. Ancon's Teplo tie has negligible thermal conductivity and hence heat loss. They are available in a range of diameters and lengths to suit partial and full-fill cavities from 50mm to 450mm and Type 1 to 4 applications.

Helical Wall Ties

Helical wall ties are ideal for anchoring building façades, structural members as well as stabilising multiple width brick walls. Helical wall ties are used in thin-joint construction, where the joints between the large-format aircrete blocks are only 3mm thick, preventing the use of traditional ties. You install them by drilling a pilot hole into the outer and inner substrate. Using the special SDS adaptor on a hammer mode only setting, you then drive the tie into the substrates. Helical ties are generally suitable for Type 2 and 3 applications.

Retaining Clips

Insulation retaining clip is suitable for use with wall ties to be used in partial fill cavities. It can be used with most stainless steel ties.

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Video credit:https://www.youtube.com/watch?v=MsuGfktl80c&t=172s