Cavity Ties (16)

Cavity Ties: Your Comprehensive Guide To Brick Wall Ties

Our selection of fire-resistant brick ties and de-bonding sleeves play a vital role in ensuring the stability of a building and are suitable for use in all types of buildings of any height in the British Isles in line with NHBC standards.

Cavity ties are commonly made from corrosion-resistant, stainless steel and are designed to optimise the structural safety of a building. The placement and spacing of wall ties differ around windows, doors, roof verges and movement joints as specific locations like these require closer cavity tie spacing.

Masonry wall ties are designed to efficiently distribute the weight of the wall evenly across both layers, thus reducing the risk of bowing, bulges or cracks. Without wall ties, the two layers of a cavity wall would be vulnerable to structural failure, as they would not be properly connected.

For more information regarding product specification and suitability, please click on the links below or contact the helpful sales team at C&W Berry. We also sell a vast range of Bricks from engineering to classic facing and supply a broad range of building and coursing bricks from leading manufacturers including Ibstock, Forterra and Weinerberger.

The following brief guide will help to provide further information relating to cavity ties, including their type, functionality, installation recommendations and tips for optimal performance.

Table of Contents

1. What Types of Cavity Ties Are There?
2. How Do I Choose The Right Cavity Ties?
3. What Are The Common Mistakes When Choosing Cavity Ties?
4. How Should Cavity Ties Be Maintained?
5. Why Should I Use Cavity Ties?

1. What Types of Cavity Ties Are There?

Cavity ties are used to connect the two leaves (inner and outer) of a cavity wall to ensure structural stability and load transfer between the leaves. There are several types of cavity ties, categorized based on their design, material and function. Here is a brief summary:

Type by Shape and Design:

• Standard (Strip) Ties: Flat, narrow metal strips often with a twist or corrugation to improve grip
• S-Shaped Ties: Formed like an 'S' to allow some movement and accommodate differential expansion
• Ladder Ties: Shaped like a ladder with horizontal rungs connecting the two wall leaves
• Butterfly Ties: Have a butterfly-shaped profile to resist shear forces
• Cranked Ties: Have bends or offsets to navigate obstacles or accommodate insulation thickness

Type by Material

• Stainless Steel Ties: Highly durable, corrosion-resistant and used in most modern cavity walls
• Galvanized Steel Ties: Steel coated with zinc for corrosion resistance and used where mild corrosion protection is sufficient
• Plastic or Composite Ties: Used in certain applications but less common due to lower strength
• Mild Steel Ties: Sometimes used but prone to corrosion so generally avoided

Type by Function:

• Movement (Flexible) Ties: Allow slight movement between leaves, accommodating thermal expansion or settlement
• Rigid Ties: Provide fixed connections, used where movement is not expected or desired
• Insulated Ties: Have a built-in insulation element to reduce thermal bridging

C&W Berry supply several different types of masonry wall ties, each designed for specific construction requirements. They can be broadly categorized by material, design and application.

2. How Do I Choose The Right Cavity Ties?

Choosing the right brick tie from C&W Berry is crucial for the structural integrity and performance of the two leaves of the wall to ensure that they act in unison to resist loading and are structurally stronger. Here is a concise summary to help you choose the right cavity ties:

• Material: Stainless steel is the most common and preferred choice as it resists corrosion and lasts longer. Galvanized steel is sometimes used but can corrode over time, especially in damp environments whilst plastic is used in some situations but is less strong or durable
• Size and Length: The tie must be long enough to span the cavity and embed properly into both leaves (usually 50mm into each leaf). The size depends on the cavity width, as common cavity widths range from 50mm to 150mm, so choose accordingly
• Type of Tie: Through ties are simple flat or twisted ties that go straight through the cavity and insulated ties have a plastic sleeve or insulation to reduce thermal bridging. Expansion ties allow some movement for thermal expansion whilst adjustable ties can be cut or bent on-site to fit the exact cavity width
• Wall and Cavity Type: For solid masonry use standard ties and for insulated cavities use insulated cavity ties to minimize heat loss. For high-load or tall walls, stronger, heavier-duty ties could be necessary
• Building Regulations and Standards: Check Building Regulations as they often specify minimum requirements for cavity ties. All ties should comply with BS EN standards (like BS EN 845-1)
• Spacing: The spacing between ties affects wall stability and generally speaking two and a half wall ties per square metre of masonry are required. Follow the recommended spacing (e.g. 900mm maximum horizontal and 450mm maximum vertical, however, this may vary if required by Building Regulations) and make sure your tie type supports this spacing without sagging or failure

Consider the cavity tie material, as stainless steel (grade depends on environment) is commonly the preferred choice due to their corrosion-resistance. Check that the cavity tie is long enough for the cavity, including embedment and match to cavity width and wall type. Consider insulated ties if thermal bridging is a concern and check that the cavity ties comply with Building Regulations and are compatible with the insulation material. Consider the building's height, location, wind exposure, cavity width and masonry type and consult with an architect, structural engineer or competent installer for guidance, especially for non-standard constructions.

3. What Are The Common Mistakes When Choosing Cavity Ties?

When choosing cavity ties from C&W Berry several common mistakes can compromise the structural integrity and durability of the building. Here is a brief list of the common key errors to avoid:

• Incorrect Material Selection: Using ties made of inappropriate materials (e.g. untreated steel instead of stainless steel or galvanized steel) can lead to corrosion, especially in damp environments. Not considering environmental conditions (e.g. coastal areas require more corrosion-resistant materials)
• Wrong Tie Size or Length: Selecting ties that are too short may not adequately connect the inner and outer walls, reducing structural stability. Oversized ties can be difficult to install correctly and may cause damage
• Improper Tie Spacing: Placing ties too far apart reduces the bonding strength between the two wall leaves, weakening the structure. Too close spacing can be unnecessarily costly and may interfere with insulation
• Ignoring Building Regulations and Standards: Not adhering to Building Regulations regarding tie types, spacing and corrosion resistance can lead to non-compliance and safety issues
• Neglecting Thermal Bridging: Choosing ties that create a significant thermal bridge can lead to energy loss and condensation problems within the cavity
• Not Considering Wall Movement: Using rigid ties in areas where some movement or differential expansion between leaves is expected can cause cracking
• Failure to Account for Cavity Width: Selecting ties that don’t fit the cavity width properly can result in inadequate embedment into both leaves or excessive projection
• Poor Installation Practices: Even the right tie can fail if installed incorrectly e.g. if not fully embedded, damaged during fixing or if it is misaligned

The main cause of brick tie failure is the rusting of metal ties, not installing the required number of ties or failure to properly bed the tie in the mortar joint, which also reduces the bond strength. Other common oversights include using the wrong type of mortar or cavity tie for the application, insufficient tie quantity or incorrect tie placement around openings.

4. How Should Cavity Ties Be Maintained?

Cavity tie connectors are used in cavity wall construction to tie the inner and outer walls (leaves) together, ensuring structural stability and load distribution. Proper maintenance of cavity ties is important to avoid structural issues like wall separation, bulging or cracking. Here is a brief summary to help you ensure they remain highly effective:

1. Regular Inspection: Inspect cavity ties periodically (every 5-10 years or after severe weather events). Look for signs of corrosion, rust or damage and check for loose or missing ties
2. Check for Corrosion: Cavity ties are often made from stainless steel or galvanized steel to resist corrosion, but over time, moisture or chemical exposure can cause rust. If corrosion is found, assess the extent and consider replacement
3. Monitor Wall Movement: Look for cracks, bulging or separation between inner and outer walls, which might indicate failing ties. Use professional advice if structural movement is suspected
4. Replacement and Repair: Replace corroded or damaged ties with new stainless steel or appropriate corrosion-resistant ties. For extensive damage, professional structural assessment and repair may be necessary. In some cases, retrofit wall ties can be installed through drilling
5. Moisture Management: Ensure that cavity wall drainage and weep holes are clear and functioning to prevent moisture buildup. Keep gutters and downpipes in good condition to avoid water ingress
6. Documentation: Keep a record of inspection dates, findings and any maintenance or replacements done

Inspect masonry wall ties from C&W Berry regularly for corrosion and damage, particularly those in buildings built prior to 1981, as they had less rust protection, and replace any compromised ties promptly. Maintain good cavity drainage to reduce moisture exposure and seek professional advice if wall integrity issues are observed.

5. Why Should I Use Cavity Ties?

Cavity ties are metal connectors used to join the two separate, inner and outer leaves of a cavity wall together. The cavity is the actual gap between these two walls and here a few of the important reasons to use these reinforcing brick ties:

1. Structural stability: They help keep the two leaves of the cavity wall connected and stable, preventing them from moving independently or collapsing
2. Load transfer: Cavity ties transfer lateral loads (like wind pressure) from the outer wall to the inner wall, improving the overall strength of the structure
3. Prevent bowing and bulging: Without ties, the two walls can bow or bulge outwards or inwards, which can cause structural damage and cracking
4. Maintain cavity width: They ensure the cavity gap stays consistent, which is important for insulation and to prevent moisture bridging
5. Moisture control: Properly designed cavity ties help prevent moisture from travelling from the outer leaf to the inner leaf, keeping the inside dry
6. Corrosion resistance: Good cavity ties are made of stainless steel or galvanized steel to prevent rusting, which helps the wall last longer

Use masonry anchors from C&W Berry to securely and safely connect two cavity walls, to maintain wall integrity and efficiently transfer loads. They are essential for building strong, durable and weather-resistant walls and will help to maintain proper ventilation and prevent moisture build-up within the cavity, contributing to energy efficiency and damp prevention of the building.

For further technical information relating to our range of cavity ties, please telephone our main sales line on 01772 431 216 or email [email protected].