Construction of wall cavities has been used since the beginning of the Nineteenth Century and became part of the normal building practices from around the turn of the century until current day.
The primary benefits of the construction of cavity walls are:
Insulation for thermal energy
Sound insulation
Blocks water from the outside.
to give structural strength and stability.
In order to permit the evaporation of water from the structure
While the building materials and techniques of cavity walls differ, they all depend on a tying system to join the leaves on the inside and outside and to give the wall the strength and stability. So, cavity wall ties constitute the primary structural element in cavities.
The past was when a wide variety of materials were used in wall ties. This included in some areas slate and wood. The most popular materials used in the last decade of the Victorian time period have been mild steel or iron but it’s the destructive characteristics of these types of tie which have caused the most trouble.
There is a common misconception that houses built post 1981 are not at risk from the threat of corrosion in wall ties and the associated issues. This is due to the fact that after this date, wall tie wires were of an improved specification, typically galvanised or stainless steel While this decreases the chance of failure, but it doesn’t entirely eliminate the risk.
Corrosion:
The older kinds of tie are either without a protection coating, or may are coated with a bituminous, or thin Zinc coating. Whatever the case, they are extremely susceptible to rust in conditions of humidity or oxygen. The degree and speed of corrosion will depend on a number of aspects, including
Exposure to weather patterns
Type of mortar : Black Ash and weak mixes, as well as porous lime mixes
Pointing condition
Inadequate design, construction and layout, blockage of cavities, no DPC’s or membranes
Environmental aspects, including the costal areas.
Wall tie corrosion could result in a scenario that varies in severity from the upcoming maintain the ace, to a complete crumble of the building. As ties age, they expand and this corrosion can cause distinctive horizontal cracks within joint joints of mortar generally, but not limited to the leaf’s outer. This is usually associated with the heavier metal and Fishtail types of ties.
Wire ties as well as other thin metallic ties will not expand enough to cause horizontal cracks, as long as the joints in mortar beds are extremely tight(thin) or the mortar is that are very hard. Horizontal cracks could severely weaken structures of the building as well as increase speed of corrosion increasing the exposure of the ties moisture.
Contact northwestwallties.co.uk when searching for wall tie replacement near me.
Wall tie density:
The structure of the wall ties found in the majority of older homes is usually discovered to be irregular, and the overall density of the ties is usually not sufficient. This can lead to regions of great concerns and weak spots within these types of structures These areas are typically
Windows’ sides and doors
Eaves and Verge levels
In the past, there was no tie allowance in these areas, and as stated, this could cause weaknesses within the structure.
Wall tie survey:
The main elements of Wall tie surveys are:
Location and approximate age the property’s location and approximate age
Determine the methods of construction, cavity or brick construction. Materials for the outer and inner leaf. The design of the wall can alter inside the wall for instance, in north-easterly areas. North East it is common for walls at ground level to be converted into cavity walls when they reach the one floor. For cavity brick walls to change to solid walls when eaves are placed on a gable-end peak.
Mortar type and condition , and the general state of the pointed
The width of the cavity
The wall insulation is present in the Cavity?
Check for cracks and other obvious evidence of movement. Also, note any bowed or bulging walls
Be particularly attentive to horizontal cracks which have been fixed and repaired and
Determine the pattern and the density of existing connections
Determine the condition of the existing ties as well as the severity and extent of any corrosion
Does the location of corrosion-prone ties match the site of any cracking that has been previously noted?
Differentiate between cracks caused by corroded tie ties and cracks caused by other types of corrosion-prone metals, such as cast iron, steel lintels down pipes etc.
Wall tie embedment Are the wall ties sufficiently long to accommodate the cavity’s width and are they in the correct position
Equipment:
The surveyor is armed with many of the necessary equipment for an extensive survey and investigation.
Metal detector to locate ties
Drilling with a cordless hammer drill to inspect holes
EndoscopeOr Boroscope to study ties at-situ
Mastic or Mortar for making great drill holes
NB Cavity wall insulation is another issue in homes with cavity insulation . It’s required to take a brick to examine the wall ties. This will cost PS60.00 plus VAT at the rate of the moment.
Wall tie stabilisation:
After all the outcomes of the survey are assessed, it will be time to move on to the next step which could be anything from not taking any action until the ties are free of corrosion and functional, all the way to the entire reconstruction of the structural walls. The most cost-effective treatment is generally somewhere in between the two extremes.
Specific recommendations are provided in Building Research Establishment (BRE) Digests 329 & 401 and British Standards Institute (BSI) D140.
The most frequently used treatments for remediation are:
A complete wall tie replacement is advised if the ties exhibit signs of significant corrosion and where visible corrosion in the course of inspection
For the majority of walls, the suggested fixed density of 2.5 tie/m2 and further ties at 300mm vertically centred at the edges of the openings and at the top the verges
In the case where the ties currently in place are made of thin metal or wire butterfly type, which might cause horizontal cracks It is normal for them to remain in the same place.
If the corrosive nature of ties has caused cracks to the leaf’s exterior the ties must be removed or separated structurally from the leaf. This is only possible following installing remedial tie and is generally the most expensive and time-consuming aspect of stabilisation of wall tie.
It could be that the wall tie is in good shape however they are not dense It could be in instances like this that additional ties can be installed to enhance and reinforce the existing tie.
Installation of a wall tie for a second time:
A variety of remedial tie options are readily available, and it is essential that to choose the correct tie for every property. The choice should depend on outcomes of the survey, and specifically the outer and inner leaf cavities and the thickness of the substrate.
A standard product does not cover all possible scenarios and, even with the advantage of an accurate survey installers will be prepared to deal with a variety of construction variations
In certain instances, ties could be put in from the inside of the building if significant changes or renovations are being carried out. This is a great option since there aren’t any obvious signs for replacement after the works are completed.
When holes are made through the middle of bricks with outer leaf, it is crucial to ensure the closest match possible using dyeing mortars on the spot. Our workers have been trained and are extremely proficient in this particular aspect of remedial work.
Experience and supervision of the operator is vital to ensure that the ties are properly installed and the job is finished on time and effective.
Treating existing relationships:
When the repair demands an alteration to the existing ties they must be identified generally using an instrument such as a metal detector, and/or the Boroscope
Removal of all tie is required when there is a significant amount of damage to both the inner and the outer leaves. This will require replacing and removing the individual bricks. This is slow and labor intensive, and could cost you a lot.
If the damage is restricted to the leaf’s outer surface, you can isolate structurally the tie and mortar bed joints. There are a variety of methods to use such as the use of isolation sleeves, either made of made of foam or plastic.
NB that if your property needs general repointing, it’s beneficial visually and financially to carry out these projects in conjunction with treatments for existing wall ties.
The installation of a wall tie is a solution that’s technical to a frequent issue with durability and structural strength that is commonly encountered with cavity wall constructions. It shouldn’t be attempted by non-experts and should not be used as DIY solution. As with other remedial procedures like mold, damp, and woodworm elimination. One of the main aspects that the customer pays for is assurance that the job was completed by professionals and that the house is safe for habitation and will keep its market value.
