Anyone can make a repair to a cavity wall tie, and they can be purchased on the internet to use an easy DIY solution. Why do architects, structural engineers as well as local authorities’ mortgage lenders require for a specialist’s help to install this?
There are several excellent reasons …..
Cavity wall tie ties are vital to the stability and safety of any cavity wall. They are installed by the bricklayer when they construct the masonry. this is the norm for more than a century in building cavity wall ties across the UK.
The process of constructing wall ties to the wall once it’s constructed is easy and there’s very little that can go wrong (though mistakes can happen even in newly built homes). However, installing wall ties into existing structures is a different matter.
Before deciding to install new remedial cavity wall ties are some of the factors to be taken into consideration:
What spacing should be used to determine how tie-ups be repaired?
How much length should the wall ties be, in order to accommodate the wall’s thickness as well as the size of the cavities?
How well exposed is the structure and do the numbers above of wall ties have to be revised?
What is the building material that is used to construct the cavity wall the leaf’s inner and outer (block or stone, brick or even timber)?
What are the parts of the wall where the ties for cavity wall shouldn’t be used (there are always a few)?
Does the cavity have no obstructions or cavities wall insulation which could be contaminated due to the wall tie?
What is the best way to access the wall to allow for safe installation of wall tie, (you are responsible for your safety as well as the safety of those who are working for you)?
What size of a pilot hole does wall ties require, and how are they?
Are there surfaces such as render that wall ties need to be anchored through?
What is the best way to have the wall ties be checked, to make sure they’re functioning?
How can the appearance that the structure has kept without creating a ‘polka-dot effect?
Do the wall ties have the capacity to be able to last the lifetime of the building?
When taking this into account and having selected the appropriate cavity wall tie for both the outer and inner leaf fixation, how will the efficiency be monitored at the site?
Who will put up the wall tie and what experience has he/she received?
What tools are needed to make the pilot hole? tie them up and check them for proper functioning?
What is the record-keeping and reporting procedure for Wall tie tests?
What are the alternatives should the remedial tie fail random testing due to unanticipated causes and what would this costyou?
Then, what type of assurances will be given that covers the material and the workmanship , and is it an insurance-backed warranty?
There are many other questions that are more than the eighteen listed,, but they are important questions to ask prior to when the cavity wall tie replacement begins.
Nothing here is rocket science , so here are the nitty-gritty responses to the questions mentioned above. ….
The spacing for wall tie-ups is based on a variety of factors such as the cavity width and the length of each leaf. They can vary from the typical staggered pattern of 900mm x 450mm up to 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 wall tie density considers wind loadings as well (these are able to vary throughout the nation and also with 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. High performance may help decrease the amount of tie in the wall when structural engineers have participated in the calculations, and an extensive on-site test has been conducted to verify the installation.
Be aware that any figures for performance that are offered by the manufacturers are general and could not be applicable to your particular site. Only the wall tie tests on site will be able to determine the actual performance since the manufacturer hasn’t seen your wall and has not built it. (read the conditions and terms and you’ll find this information in the manufacturer’s data sheets)
The depth of embedment of ties is dependent on a variety of factors as well. A 50mm depth into each leaf is recommended as a minimum. However, this assumes a normal brick cavity wall, and doesn’t take into consideration the internal spalling of the face (caused through the drilling percussion of the outer leaf, which creates the brick chip from the rear of the skin’s outer layer – which reduces the wall’s thickness at this point). This penetration serves as an indication only, and usually 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 anchors made of resin/grouted to lessen the ‘bearing’ stress). The timber frame houses are unique instance, and a rigorous, random tests are necessary to measure the depth of fixing required for a satisfactory fix for the studs of timber. It is natural substance and has a range of strength within the same structure, dependent on the amount of sapwood and the precision of the building.
There are numerous charts that illustrate the building’s exposure to wind gusts and naturally when buildings are high-rise, loads will be greater. These are also higher in homes, where the two houses, for example, are constructed with gaps between the gables (common in numerous housing estates) which results in an effect of wind funnelling, which is a major tension on the wall tie since the wind speed decreases the air pressure and forces the gables. This requires an increase in density that will increase the number of wall ties that are normally required.
Wall ties must be flexible enough to allow the skins on the inside and outside of the wall to move differently. Because of this, areas of houses must be avoided as the new ties can cause stress fractures because they are unable to move. Any hidden utilities must be avoided as well. There aren’t any pipes or cables in the cavity, however they’re more prevalent than you think, and drilling into a cable to put in a cavity wall tie can be fatal.
The cleanliness of the 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 specifications will have be updated to take into account this. Cavity wall insulation, in particular is often ignored by wall ties installers as well as DIY homeowners. The reason is pollution of insulation. The insulation is typically older foam or modern fibre or bead types. It is a flexible, light product that is designed to minimize heat loss and permit water vapour to flow throughout the cavity in a fluid manner.
Installing remedial wall ties is always accompanied by some substance being ejected from the cavity. It is a mixture of brick dust or stone powder (drill spoil) that is ejected from the inner and outer leaf (a 12mm hole, 100mm wide in its outer layer and 60mm deep inside results in approximately 19cm3 worth of drilling spoil). But, the drill spoil is naturally aerated and is subsequently weighed down by air, and the pile is much greater than it. The majority of it is released to the exterior walls (into your face while you drill) however, the rear area (including any spalled face on the rear that could be large, see the previous paragraph) as well as all of the debris from the inside leaf, are blown through the hole. This isn’t a problem in the case of a cavity that is empty, as dust won’t cross a damp proof course, or cause bridges. However, it is a different matter 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 an unclean snowball. There are a few at every wall tie location and every wall tie isolation point when you are isolated from the rusty cavity wall tie too. The impacts on insulation can be very grave.
Insulation is compressed because of material, making it more dense than. Additionally, the debris transfer moisture and heat very effectively. Therefore, a couple 100 or more wall-ties could 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 cause issues. A few minor variations in the insulation cause cold spots appear (surveyors refer to this as cold Bridging) and be caused by high humidity result in mould to grow and damp patches to appear on the interior of walls. The problem gets worse …. leaving debris in place allows water to move through the cavity (cavity bridge) and can exacerbate the situation by flooding the insulation, or in more severe cases , creating penetrating damp inside. All cavity wall ties that are remedial come with a drip feature. They vary in design but all function by causing rainwater to drain off of the wall tie, before it has the chance to penetrate the skin of the wall and result in damp. In insulation that has been contaminated, the drips just fall on the snowball that is contaminated and can cause more damage.
In the event that insulation exists, additional 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.
Secure access for wall tie replacement.
Installing wall ties is drilling both hands at heights across the building. The risk of falling from a height remains the most fatality in the construction industry and the most frequent causes are ladder injuries and DIY accidents. Testing of wall ties requires both hands , and notes or photos are required to be taken. To do this, the use of a scaffold tower or fixed tubular scaffolding is required. The danger of hitting hidden service lines implies that only double-insulated equipment and 110v centretapped to earth machines need to be taken into consideration. The condition of the soil 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 also important. The site is extremely noisy and it can also be dusty.. It is important that neighbors are advised.
If the wall has been rendered pebbled, pebbled or coated with any substance it will reflect on the process of installing wall tie as well as the type of tie used to repair it. First is the wall’s material in good condition? 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. It is recommended to use a repairable cavity wall tie made for expansion by mechanical means is not recommended, as with no care and a lot of failed holes that could eventually be drilled near the edges of a bed joint, and post-torsion expansion may cause damage to the fix (see below) and render 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 similar to a rawlbolt. If the material is unable to take these forces, the material fails and the fixing is damaged. Therefore, the majority of manufacturers of wall ties suggest that fixing the wall ties at the ‘centre of brick’ or the centre of brick, which is difficult to do when the brick is hidden in render (not to mention the inside leaf that is never visible).
In the event that render has been present in the area, then non-expanding wall ties are recommended for example: resin-bonded wall ties that have both skins Helifix ResiTie, or resin and friction fix, like that of Helifix RetroTie (friction fix inside leaf, that is able to be tested independently of the outer leaf) which is followed by the resin fixation in the outer leaf.
The primary material used for wall ties used for remedial purposes are made of stainless steel. In practice, they should not be corroding. However, there are situations where more precautions are required, and a superior quality stainless steel 316 grade commonly called’marine grade’, should be used. This is the case for coastal zones, contaminated sands as well as on certain prestige or historical buildings in which a long-lasting life is stipulated (we have installed Cintec the 316-grade stitching anchors on York City walls, after the 500 year life span was stipulated). A higher grade of stainless is employed in a few friction-fix wall ties that are helical especially those that fix with one move and via the outside skin, and into the leaf’s inner. But I don’t specify the wall ties because of the possibility of failure of the leaf fix. This cannot be tested randomly.
Testing? This is vital for any remedial wall tie installation. The process is generally simple tension tests to determine if the wall tie is gripping the masonry in a way that they meet the requirements of the design. The new wall ties constructed by a bricklayer are not required to be tested. They are easy to install on an open bed-joint. What could happen? 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 perfect Wall tie often do not provide the desired solution – this is true for all of the wall ties that are available from experts or through the internet. My suggestion is that if wall tie is not tested, do not use them. The reason is that homes vary and bricklayers differ mortar mixes differ as well as the overall quality of the walls are an issue. The leaf inside can be soft blockwork or the rock-hard engineering brick. All wall ties that are remedial have flaws and there isn’t single wall tie that is suitable for all scenarios. Only through on-site testing is anyone able to detect some odd houses where the ties do not conform to exactly what was stated on the Tin’.
A tension testing equipment costs approximately PS700 plus VAT. Because every job requires testing, an expert in wall tie could have several and have one that is available for all contracts. Additionally they are carried from vans, as well as on windy scaffolds , they are damaged and lose their accuracy. This is why they have to be calibrated at minimum each year and could cost more than PS100 every time. Only an expert who uses them regularly can justify the cost. Although they are able to get hired out, usage of them requires an understanding and some knowledge. An extensive selection of adapters that can be used to accommodate the vast variety of remedial wall ties that are available is essential too… It’s no use owning a rig when you discover your wall tie 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, to the fullest extent of 100% in extremely difficult situations or in masonry with special specifics. It’s not worth testing without a pass-or-fail figure. The range of this can be from 1Kn up to more, based on the test.
Be aware of the reasons tests are performed. It’s about getting a perfect job, and also gaining credibility for the wall tie job. There should be a solid method of recording the gauge readings. It should be recorded, however it can be augmented with photographs of measurements and test positions. I’ve been incorporating the photography method to our method for around 16 years, and it’s being adopted by different wall tie professionals.
What happens if tests show an error? In a way it’s a good thing 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 method of installation; perhaps you should drill a larger hole? If this isn’t feasible then how about a small increase in the wall tie’s density? In the opposite, it could be that the wall tie isn’t suitable for the wall you are looking at What alternatives are there? Could they be tested with and a change in specification that is authorised? These are the kinds of decisions that experienced wall tie installers and experts must make, therefore having educated, well-briefed and certified 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 job is suitable for the task. This is the reason City and Guilds designed a level 2 National Vocational Qualification for wall tie technicians. 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 contractor or DIY project was completed it isn’t an choice. In most cases, these tasks require a guarantee typically with a guarantee of 20 years. This should be only a last resort to cover failure, and when the work has been performed in line with the standards laid in the previous paragraph, does it actually necessary?
The answer is yes. The reason isn’t to be defended. The reason is so that the problem of wall tie corrosion could be put aside and put aside. The houses are sold and bought and mortgages are renewed by other lenders and loans are issued against property due to a variety of reasons. A solid insurance-backed assurance ensures that these transactions will go on without fear of corrosion to the wall tie being brought into the mix. The documentation you have on hand, including the insurance policy, and other 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 an insurance policy that is backed by the guarantee is essential. Guarantee protection insurance is available through any reputable specialist contractor and is essential for me.
Here’s a quick overview of how to install a wall tie from a practical point of view. I hope you find it useful
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