Anyone can make a repair to a cavity wall tie, and they are readily available on the internet to use an DIY method. What is the reason, architects, structural engineers and local authorities’ mortgage lenders require for a specialist’s help to install this?
There are several positive reasons …..
Cavity wall ties are essential to the stability and safety of any cavity wall. They are installed by the bricklayer while they build the masonry, and it has been the standard procedure for more than a century in building cavity wall ties across the UK.
Making wall ties for the wall once it’s constructed is easy and there’s nothing to be wrong (though errors do occur even in newly built homes). However, installing wall ties into existing structures is an entirely different issue.
Before you decide to install new cavity wall ties, here are some aspects that have to be taken into consideration:
What distance should the fix ties be?
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 do the numbers above of wall ties have adjustment?
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 that cavity wall ties are not permitted to be put in (there are always a few)?
Is the cavity free of particles or insulation for the cavity walls that could be contaminated by the wall tie?
How easily can the wall be reached to allow for safe installation of wall tie, (you are responsible for your own safety and for the security of the workers who are working for you)?
What size of a pilot hole will the wall ties require and how are they?
Are there any finishes, such as render, which wall ties need to be secured through?
What is the best way to have the wall ties be checked, to ensure that they are functioning?
How can the appearance that the structure has maintained without creating a ‘polka-dot look?
Do the wall ties be able to last the lifetime of the building?
In taking the above into consideration and having selected the appropriate cavity wall tie for both the outer and inner leaf fixation, how will the effectiveness of the fix be measured on the spot?
Who will be installing the wall ties ? What experience has he/she received?
What equipment is required to make the pilot hole, tie them up and check them for proper functioning?
What is the reporting and recording procedure for test of wall ties?
What happens should the remedial tie fail random testing due to unanticipated causes and what would the cost be?
Then, what type of warranty will be provided for the materials used and the workmanship , and is it an insurance-backed assurance?
There are other questions that are more than the eighteen listed,, but they are important ones to be asked before the replacement of a wall tie begins.
For more information on cavity wall tie replacement visit this website…
Nothing here is rocket science , so here are the short solutions to the questions above. ….
The spacing of the wall tie depends on a mix of variables such as the cavity width and the size of the leaf. They can vary from the typical staggered pattern of 900mm by 450mm to as small as 450×450 in certain situations. There are certain areas of the wall that require particular attention, for example the exposed reveals that are not tied around windows or verge locations. The density of the wall tie is based on wind loads too (these may vary across 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 tie are required; an increase in the density of wall tie. The high performance could help decrease the amount of tie in the wall in the event that structural engineers have participated in the calculations as well as an extensive on-site test has been done to validate the installation.
Be aware that any figures for performance that are offered from the manufacture are general and could not be applicable to your specific site. Only test on-site of the wall tie will reveal the true performance of the wall because the manufacturer hasn’t seen the wall, and he has not built it. (read the terms and conditions , and you’ll find this information in every manufacturer’s cavity wall tie data sheets)
The depth of the ties’ embedment 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 normal brick cavity wall, and doesn’t take into consideration spalling in the face (caused due to the impact drilling within the leaf’s exterior, which is essentially blowing the brick chip from the rear of the outer skin , thus reducing the thickness of the wall at this point). This penetration serves as intended to be a guideline only, and in most cases deeper tie penetrations are required. For 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 stress of bearing). The timber frame houses are particular instance, and a rigorous, random tests are required to determine the level of fixing needed for a satisfactory fix for the studs of timber. The timber is an organic product and has a range of strength in the same building according to the sapwood content and the precision of the construction.
There are graphs that show the vulnerability of buildings to the wind’s prevailing direction and naturally the load of buildings with higher rises are higher. These are also higher in homes, where for instance , two houses are constructed with gaps between the gables (common in numerous housing estates) which results in an effect of wind funnelling, 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 skins on the inside and outside of the wall to move in a different way. This is why areas of houses must be avoided. Otherwise, the new ties could cause stress fractures because they are not able to withstand this movement. Any hidden utilities must be avoided as well. There aren’t any pipes or cables in the cavity, however they’re more frequent than you think, and drilling through cables to connect a wall cavity tie can be fatal.
The cleanliness of the existing cavity is another thing to think about prior to installing the cavity wall tie-ups. When the space is stuffed full of debris or insulation, the specifications will have include this. Cavity wall insulation is a particular issue that is not considered by many wall ties installers as well as DIY enthusiasts. The problem is infiltration of the insulation. Insulation is generally old-fashioned foam, or the modern fibre or bead types. It is a flexible, light product that is designed to minimize heat loss and permit the passage of water vapour through the cavity without restriction.
The installation of wall ties for remedial purposes can result in kind of material being ejected out of the cavity. This is the result of stone dust and brick powder (drill spoil) in the leaf’s inner and outer edges (a 12mm hole, 100mm wide in its outer leaf and 60mm deep in the inside results in around 19 cm3 drill spoil). However, the drill dust is air-conditioned which means it is bulked by air, and the pile is much larger than the amount of dust. The majority of it is ejected out to the side walls (into your face when you drill) However, the rear portion (including any spalled face on the rear which could be very massive, as you can see in the above) as well as all of the debris from the inside leaf, are blown in the cavity. It’s not a problem when the cavity is empty, as dust will not cross a damp proof course, or cause bridges. However, it is a different matter inside the cavity that is insulated.
Inside the cavity, the drill spoil can’t disappear and remain in place. The result is similar to an unclean snowball. There are a few at every wall tie location and at each wall tie isolation location in the case of isolating the cavity wall ties as well. The consequences on insulation can be very severe.
It is compressed due to material, making it more dense 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 as significant in terms of financial cost however from a condensation point of view, it could result in issues. A few minor variations in the insulation cause cold spots appear (surveyors call this cold bridges) that can be caused by high humidity lead to mold growth and damp patches to appear on the interior of walls. The situation gets more severe …. Leaving debris that is too large in the cavity allows water to move through the cavity (cavity bridge) and can exacerbate the situation by flooding the insulation, or in extreme instances, causing internal damp to penetrate. All wall ties for remedial use include a drip feature that is included. They vary in design but all function by causing rainwater to drain off of 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 has been contaminated, and worsen the situation.
If there is insulation, further measures should be taken to reduce contamination of the cavity. This can be done by altering the installation procedure, and removing debris by introducing additional measures on the spot.
Access to the wall tie in a safe manner for replacement.
The installation of wall ties requires drilling both hands at different heights throughout an entire building. Falls from heights is the leading cause of death during construction, and the most frequently cited causes are ladder injuries and DIY-related accidents. Testing the wall ties requires both hands , and photographs or notes are required to be taken. To do this, an elevated scaffold or fixed tubular scaffolding is required. The danger of hitting hidden cables is the reason why only double-insulated equipment and 110v centre-tapped to earth machines need to be taken into consideration. The condition of the ground slopes, overhangs, slopes overhead power cables as well as obstructions such as conservatories and the like, are just a few things that a skilled wall tie expert will consider. The presence of customers, children or visitors who are working on the site is crucial too. The site is extremely noisy and it can also be dusty.. It is important that neighbors are informed.
If the wall is painted pebble-dashed or coated with any substance it will reflect on the way to install the wall tie and the kind of tie that is used for remedial purposes. First Is the material sound? The drilling process causes vibrations, and it can break or loosen old render. There could be pipes or services beneath the coating? A metal detector can help. A remedial cavity wall tie that is designed for expansion by mechanical means should be avoided because in the absence of extreme care and numerous failed holes in the future, some of them will always be drilled close to the bed joint (where post-torsion expansion could cause damage to the fix (see below) and render the wall tie ineffective and an unnecessary waste of time and money. Mechanical expansion ties function by generating an expansive force that extends to the outside, via the stone or brick similar to a rawlbolt. If the material is unable to take these strains, it fails and the fix becomes affected. Therefore, the majority of manufacturers of wall ties suggest that fixing the wall ties “centre of brick” to the centre of brick, which is difficult to do when the brick is hidden beneath render (not to mention the internal leaf, which is always hidden).
If render exists, only non-expansive wall ties must be chosen like resin-bonded wall ties with both skins Helifix ResiTie or a combination of resin/friction fixlike that of Helifix RetroTie (friction fix in the inner leaf that can be tested independent of the outer leaf) and then followed by a resin fix in the outside leaf.
The main material used in wall ties used for remedial purposes are made of stainless steel. This means that , in the real world, they shouldn’t corrosion-proof. But there are situations where more security measures are required and superior quality stainless steel 316 grade is often called’marine grade’, should be used. This is especially true for coastal areas, areas with contaminated sand, and also on some prestigious or historical buildings with a long lifespan is required (we have installed Cintec Stitching Anchors 316 Grade on York City walls, after the 500 year life span was stipulated). The higher grade stainless is employed in a few friction-fix wall ties that are helical especially those that fix with one move and by putting the skin on, and into the leaf’s inner. However , I haven’t specified the wall ties because of the potential failure of the leaf fix, which can’t be tested in random ways.
Testing? It is necessary for all wall tie installations that require remedial. The process is generally simple tension tests to ensure that the wall ties are firmly gripping the masonry enough to meet the requirements of the design. Wall ties that are new and constructed by a bricklayer don’t require to be tested. They are easy to install on an open bed-joint. What could be wrong? The installation of a wall tie for remedial purposes is distinct. There are many things to be avoided. Even if you take your time selecting the perfect Wall tie can don’t provide the solution. This is the case for all common wall ties sold by specialists or on the internet. My suggestion is that if wall tie is not tested, do not use them. The reason is that homes vary the bricklayers, bricklayers are different mortar mixes differ in quality and wall quality is an issue. The inner leaf may be soft blockwork or rocks hard engineering brick. Each of the remedial wall ties has weak points and there isn’t single wall tie that can be used in every situation. Only through on-site testing is anyone able to detect some odd houses where the ties aren’t doing as they stated on the Tin’.
A tension testing equipment costs approximately PS700 plus VAT. Since each job is subject to testing, an expert in wall tie could have several and have one on every contract. Additionally they are carried through vans, as well as on scaffolds that are windy – they are damaged and lose their accuracy. Because of this, they need to be calibrated every each year and 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 them requires an understanding and some education. An extensive selection of adapters to work with the broad variety of remedial wall ties available is essential too… It’s no use owning a rig when you discover you’re wall ties that you’re using do not fit the. Testing can vary in the amount of testing, ranging starting with a random five percent of the ties up to the fullest extent of 100% in highly difficult situations or in masonry with special particulars. It’s not worth testing when you don’t have an acceptable pass or fail number. The range of this can be from 1Kn to a lot more, based on the particular application.
Be aware of the reasons tests are performed. It’s about doing a good job, and also gaining credibility for the wall tie. It is essential to have a reliable method of recording the gauge readings. The information must be written, however it can be augmented with photographs of measurement readings and test locations. I’ve been adding this method to our method for around 16 years and it’s being adopted by others wall tie experts.
What happens if the tests bring an error? It’s a good thing, because in a sense this is a blessing because you’ve learned the things you didn’t know in the past and you can take action to correct the issue. If the tests for tension are not quite on target, it is possible to look into the way to install it; perhaps the hole should be deeper? If this isn’t feasible what about a slight increase in the wall tie’s density? However, it could be that the wall tie is not suitable for the wall you are looking at So what other options are there? Are they able to be tested in conjunction with and an approved specification change? These are the kinds of decisions that certified wall tie installers as well as specialists must make, therefore having trained, properly briefed and competent personnel will be able to take this into consideration. If a specialist contractor involved, it is important to have the support of the management team; putting the right systems that allow for, or anticipate, these issues will ensure that the work completed 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 my technicians and I have.
After the job is completed, A guarantee is nice? Of course, if the builder or DIY project was completed it isn’t an choice. In most cases, these tasks are backed by a warranty usually with a guarantee of 20 years. It should be considered an option to cover failure, and when the work has been performed in line with the standards laid in the previous paragraph, does it truly necessary?
The answer is yes. The reason for this is not to allow it to be defended. The reason is so that the problem of corrosion in wall tie can be put aside and put aside. The houses are sold and bought and mortgages are renewed by other lenders and loans are issued against properties for a variety of reasons. A solid insurance-backed assurance ensures that these transactions will go on without the risk of wall tie corrosion getting added to the mix. The fact that you have the paperwork on hand, including the insurance policy and similar strengthens the reliability of the wall tie installation and prevents the time-consuming surveys and arguments in the future.
There is no guarantee that a company will last forever, so the need for real insurance backing for guarantees is essential. Guarantee protection insurance is available through any reputable specialist contractor and is essential according to me.
Here’s a quick overview of how to install a wall tie from a practical standpoint. I hope that you find this guide useful