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Home » Cavity Wall Tie Replacements – The Ultimate Guide

Cavity Wall Tie Replacements – The Ultimate Guide

Anyone can make a repair to a cavity wall tie, and they can be purchased online for an easy DIY solution. Why do architects, structural engineers as well as local authorities’ mortgage lenders need for a specialist’s help to install this?

There are some positive reasons …..

Cavity wall tie ties are vital for the security and stability of the entire cavity wall. They are put in by the bricklayer while they build the masonry, and it has been the standard procedure for over a century of building cavity wall ties across the UK.

Making wall ties for the wall when it’s being built is simple and there’s nothing to be wrong (though mistakes can happen in newly constructed homes too). However, installing wall ties into existing structures is an entirely different issue.

Before you decide to install new cavity wall ties, here are some of the factors to be taken into consideration:

What distance should the tie-ups be repaired?
How much length should the wall ties be, in order to accommodate the wall’s thickness and the length of the cavities?
How well exposed is the structure and will the above figures of wall ties have to be revised?
What is the material used for construction for the wall cavity the outer and inner leaf (block or brick, stone or wood)?
What are the areas of wall where the ties for cavity wall shouldn’t be used (there are always a few)?
Is the cavity free of obstructions or cavities wall insulation which could be contaminated due to the wall tie?
What is the best way to access the wall for secure wall tie installation, (you are responsible for your own safety and for the security of the workers employed by you)?
What diameter pilot hole does wall ties require, and how are they?
Are there any finishes, such as render that the wall ties will have to be anchored through?
What is the best way to have the wall ties be checked, to ensure that they are functioning?
How can the appearance and style of this building be kept by avoiding a ‘polka dot look?
Do the wall ties be able to last the lifetime of the building?
When taking this into account and having selected the wall tie for the cavity that is suitable for both the outer and inner leaf fix, how can the efficiency be monitored on the spot?
Who will be installing the wall ties ? What qualifications has he or she received?
What tools are needed to make the pilot hole? tie them up and verify them?
What is the record-keeping and reporting procedure for Wall tie tests?
What happens in the event that the remedial tie fails random testing due to unanticipated reasons ? What will the cost be?
In the end, what kind of warranty will be provided that covers the material and the workmanship , and is it an insurance-backed warranty?

There are many additional questions to ask in addition to these 18 however these questions are important questions to ask prior to when the replacement of a wall tie commences.

Nothing here is an art, but here are the nitty-gritty responses to the questions mentioned above. ….

The spacing of the wall tie depends on a mix of variables that include the width of the cavity and the length of each leaf. They range from the standard staggered pattern of 900mm x 450mm to as small as the 450×450 range in certain circumstances. There are certain areas of the wall that require particular attention, for example the exposed reveals that are not tied around windows or the verge position. The density of the wall tie is based on wind loadings as well (these are able to vary throughout the country and in relation to the height). It may also take into account the efficiency/effectiveness of the tested wall tie installation. A low performance could mean more ties will be required, which could lead to an increase in the density of wall tie. High performance may help decrease the amount of tie in the wall when structural engineers have taken part in the process, and an extensive on-site test has been conducted to verify the installation.

Make sure to note that any performance numbers that are offered from the manufacture are general and might not apply to your specific site. Only test on-site of the wall tie will reveal the true performance since the manufacturer hasn’t seen the wall, and he did not construct it. (read the conditions and terms and you’ll see this confirmation in the manufacturer’s data sheets)

The depth of embedment of ties is dependent on a variety of factors as well. In general, a 50mm hole in each leaf is recommended as a minimum. However, this assumes a brick cavity wall, and does not consider spalling in the face (caused through the drilling percussion within the leaf’s exterior, which is essentially blowing an atom of brick off the rear of the outer skin , which reduces the wall’s thickness at this point). This penetration serves as intended to be a guideline only, and in most cases more thorough tie penetration is required. In soft materials such as old clinker blocks the depth of the pilot hole or diameter could require an increase (diameter increases are particularly applicable for resin-grouted anchors in order to decrease the ‘bearing’ stress). The timber frame houses are particular instance, and a rigorous, random tests are necessary to measure the level of fixing needed in order to get a perfect fix on the studs of timber. The timber is an organic product and can vary in strength within the same structure, according to the sapwood content and the accuracy of the building.

There are numerous charts that illustrate the building’s exposure to wind gusts and, of course, when buildings are high-rise, loads will be greater. These are also higher in homes, where the two houses, for example, are built with a gap between the gables (common in numerous housing estates) creating the wind funnelling effect which is a major stress on the wall ties because the speed of wind decreases the pressure of air and pulls the gables. This will require the increase in density to more than double the amount of wall ties that could otherwise be required.

Wall ties should be flexible enough to allow the outer and inner skins of the wall to move differently. Because of this, areas of houses must be avoided. Otherwise, the new ties can cause stress fractures as they are unable to move. Hidden services must be avoided as well. There should not be any pipes or cables within the cavity, however they’re more frequent than you’d imagine and drilling into a cable to connect a wall cavity tie could result in a fatal accident.

The cleanliness of the existing cavity is another thing to think about prior to installing the cavity wall tie-ups. In the event that the area is stuffed full of debris or insulation, the design will have be updated to take into account this. Cavity wall insulation is a particular issue that is not considered by many wall ties installers as well as DIY homeowners. The reason is infiltration of the insulation. The insulation is typically old-fashioned foam, or the modern fibre or beads. By nature, it is a flexible, light product that is designed to minimize heat loss and permit the passage of water vapour throughout the cavity in a fluid manner.

Installing remedial wall ties can result in kind of material being ejected from the cavity. This is the result of brick dust or stone powder (drill spoil) in the inner and outer leaf (a 12mm hole, 100mm wide in its outer layer and 60mm deep inside creates approximately 19cm3 worth of drilling spoil). However, the drill dust is naturally aerated which means it is bulked by air, and the pile is much larger than the amount of dust. More than half of it is released to the exterior walls (into your face when you drill) However, the rear area (including any face that is spalled which could be very massive, as you can see in the above) and all the excrement from the interior leaf, are blown in the cavity. This isn’t a problem when the cavity is empty, as dust won’t cross a damp proof course, or cause the bridging. This is not the case inside the cavity that is insulated.

In the cavity that is insulated, the drill spoil is unable to be removed and remains in place. It’s like the appearance of a dirty snowball. There are a few at every wall tie position and every wall tie isolation point in the case of isolating the cavity wall ties as well. The consequences on insulation can be very grave.

It is compressed due to material, making it much denser than. The debris also transfers moisture and heat very effectively. So a few hundreds of wall tie can dramatically reduce the effectiveness of insulation. The loss of heat isn’t so significant financialally however from a condensation point of view, it could cause issues. A few minor variations in the insulation cause cold spots appear (surveyors call this cold Bridging) that can be caused by high humidity result in mold growth and damp patches on the outside of walls. The situation gets more severe …. leaving debris in place can allow water to flow through the cavity (cavity bridge) and can exacerbate the problem by soaking the insulation, or in more severe instances, causing internal damp to penetrate. All cavity wall ties that are remedial come with a drip feature. The types vary, but they all function by causing rainwater to run off the wall tie prior to it being able to get to the interior skin and create damp. In insulation that has been contaminated, the drips just fall on the snowball that is contaminated and worsen the situation.

If insulation exists, further steps must be taken to reduce contamination of the cavity. This can be done by altering the installation procedure, and removing obstructions, and implementing additional measures at the site.

Access to the wall tie in a safe manner for cavity wall tie replacement

Installing wall ties is drilling using both hands at different heights throughout the building. The risk of falling from a height remains the leading cause of death in the construction industry and the most frequent causes are ladder accidents as well as DIY-related accidents. Testing the wall ties requires both hands , and photographs or notes must be taken. To do this, the use of a scaffold tower or fixed tubular scaffolding is required. The possibility of hitting hidden service lines is the reason why only double-insulated equipment and 110v centretapped to earth machines must be taken into consideration. The condition of the ground slopes, overhangs, slopes overhead power cables and obstructions like conservatories , are all things a skilled wall tie expert will consider. The presence of customers, children or visitors working on the job is crucial too. The work can be very noisy and it can also be dusty.. It is important that neighbors are advised.

If the wall is painted pebble-dashed or coated with something that is reflective of the process of installing wall tie as well as the type of tie used to repair it. To begin with is the wall’s material in good condition? Drilling can cause vibrations and could cause cracks or shakes in old render. If there are pipes or services under the coating? A metal detector could help. A repairable cavity wall tie made to expand mechanically is not recommended, as in the absence of extreme care and numerous hole holes that are not drilled that could eventually be drilled near the edges of a bed joint (where post-torsion expansion may cause damage to the fix (see below) which renders the wall tie ineffective and is a waste of time as well as money. Mechanical expansion ties function by pushing expansive force upwards, through the stone or brick much like a rawlbolt. If the material is unable to take these forces, the material fails and the fix becomes affected. So, most manufacturers of wall ties suggest that the wall ties be fixed at the ‘centre of brick’ or the centre of brick, which is difficult to achieve when the brick is concealed beneath render (not to mention the inside leaf that is never visible).

In the event that render exists, only non-expansive wall ties must be chosen like resin-bonded wall ties that have both skins Helifix ResiTie, or resin/friction fixlike Helifix RetroTie, for example. Helifix RetroTie (friction fix in the inner leaf that can be tested independent of the outer leaf) which is followed by the resin fix in the outside leaf.

The primary material used for wall ties used for remedial purposes includes stainless steel. In practice, they should not be corroding. However, there are instances where additional security measures are required and superior quality stainless steel 316 grade is often called’marine grade’, should be used. This is the case for coastal areas, areas with contaminated sand, and also on some prestigious or historic structures in which a long-lasting life is stipulated (we have installed Cintec the 316-grade stitching anchors into York City walls, after the 500 year life span was stipulated). The higher grade stainless is utilized in some wall ties with helical friction fix specifically those that are fixed in one step that goes via the outside skin, and into the leaf’s inner. But I don’t specify the wall ties because of the potential failure of the leaf fix, which can’t be tested randomly.

Testing? This is vital for all wall tie installations that require remedial. The process is generally simple tests of tension, to determine if the wall ties are firmly gripping the masonry in a way that they meet the specifications of design. Wall ties that are new and constructed by a bricklayer are not required to be tested. They are so easy to install on an open bed-joint. What could be wrong? Installation of the wall tie in a remedial manner is distinct. There are a myriad of factors to be avoided. Even if you take your time selecting the right Wall tie can don’t provide the solution. This is the case for all of the wall ties that are available from experts or through the internet. My suggestion is that if wall ties aren’t tested, avoid using them. This is due to the fact that houses differ and bricklayers differ mortar mixes are different as well as the overall quality of the walls are dependent on the mortar mix. The inner leaf may be soft blockwork or rocks hard engineering brick. All wall ties that are remedial have weak points and there isn’t single wall tie that can be used in every situation. Only by testing on the spot is anyone able to detect some odd houses where the ties aren’t doing exactly what was stated on the Tin’.

A tension testing equipment costs around PS700 plus VAT. Because every job requires testing, the wall tie expert could have several to ensure that there is one that is available for all contracts. Additionally they are carried from vans, and on scaffolds that are windy – they are damaged and lose their accuracy. Because of this, they need to be calibrated every once a year, and that could cost more than PS100 every time. Only an expert who uses them weekly will be able to justify the expense. Although they are able to hire, usage of these ties requires skill and some knowledge. An extensive selection of adapters to work with the broad variety of remedial wall ties that are available is essential too… it’s not worth using a rig if discover your wall tie you’re using aren’t compatible with it. The testing ranges in the amount of testing, ranging starting with a random 5percent of the ties, to up to 100% in extremely difficult situations or in masonry with special particulars. Testing is useless without a pass-or-fail figure. It can range from 1Kn up to more, based on the test.

Be aware of the reasons tests are performed. It’s about doing a good job, and also gaining credibility for the wall tie. There should be a solid method of recording the gauge readings. It should be recorded, but could also be complemented by photos of the measurement readings and test locations. I’ve been incorporating the photography method to our procedure for the past 16 years and it’s becoming popular with different wall tie professionals.

What happens if tests show the possibility of a problem? In a way it’s a good thing that you know the things you didn’t know otherwise , and you are able to take the necessary steps to fix the problem. If the tests for tension are a little off target, you could look into the way to install it; perhaps the hole should be deeper? If that’s not feasible then how about a small increase in the density of wall tie? However, it could be that the wall tie is not suitable for the wall you are looking at So what other options are there? Could they be tested with and a change in specification that is authorised? These are the kinds of decisions that certified wall tie installers as well as experts must take, and having trained, properly briefed and competent personnel will consider this. If a specialist contractor involved, it is important to have the support of the management team; putting procedures that allow for, or anticipate these issues will ensure that the job is suitable for the task. This is the main reason City and Guilds designed a level 2 National Vocational Qualification for wall tie technicians. It’s something I’m very proud of saying that the technicians and myself have achieved.

Once the work is done, A guarantee is nice? Of course, if the contractor or DIY work was done this isn’t an choice. Most of the time, these jobs require a guarantee typically up to 20 years. This should be only a last resort should there be failure. So even if the work was completed in accordance with the guidelines laid in the previous paragraph, does it actually required?

The answer is yes. The reason for this is not to be defended. The purpose is to ensure that the problem of wall tie corrosion could be put aside and be forgotten. The houses are sold and bought and mortgages are renewed by other lenders and loans are made against properties for a variety of reasons. A solid insurance-backed assurance means the transactions can be completed without the risk of corrosion to the wall tie being brought into the mix. The documentation you have on hand, including the insurance policy and similar strengthens the reliability of the wall tie installation, and helps avoid the time-consuming surveys and arguments afterward.

There is no guarantee that a company will last forever, so an insurance policy that is backed by guarantees is essential. Guarantee protection insurance is available through all reputable specialist contractors and is essential for me.

Here’s a quick overview of the wall tie installation process from a practical standpoint. I hope you find this guide useful