•    Prolonged vibrations from heavy traffic or plant machinery
•    An increase in the floor loads (for example where additional floors have been added to an existing building)
•    The original walls being insufficiently thick in comparison to the building height
•    A lack of restraint between the external walls and the floor joists, beams and partitions
Bowed, leaning or bulging walls occur more regularly in older buildings. These types of properties are more prone to a decrease in wall stability because they will typically have solid walls (rather than cavity walls) which may have inadequate lateral restraint, a symptom of the construction methods of the time.

Typically, modern construction methods make use of metal strapping which connects the floors and roof to the external cavity walls. Additionally the internal walls are connected to the external walls.

You will often be able to identify a bowed, leaning or bulging wall through visual examination. Cracks may be evident at the connection of internal walls and floors with the external wall. It is important to note however, that a bowed wall without a crack will still require the same consideration as it is a dangerous fault.

In all instances, it is important to have an engineer conduct the same accurate examination of the defective wall, taking into consideration the following points:

•    The thickness and height of the wall
•    The method of restraint
•    The amount the wall is out of plumb
•    The length, width and position of any fractures – both internally and externally
•    General state of repair or disrepair
•    Evidence of historic filling of gaps between internal finishes and external wall
•    The number of openings and piers in the defective wall

The rule of thumb is that remedial measures will certainly be required when the amount of lean in the full wall height exceeds 1/6 of the thickness of the wall at the base.

There are a number of ways in which external walls can be restrained to prevent further bowing, many are disruptive for the building occupants and consequently more expensive and aesthetically unfavorable. Remedial wall tying is a less invasive, quicker and a more cost effective method of structural repair.

Remedial wall tying has been used to repair bowed, leaning or bulging walls since the early 19th Century. Early wall ties took the form of cast iron bosses (known as anchor plates) and were connected by tie rods to the opposite wall of the building, in an attempt to hold the walls vertical. Over the years, corrosion of these iron bosses has been known to cause damage to the surrounding stonework, so it is important to have these checked by an engineer if they exist in your property.

Modern day wall ties are much less invasive.   The Helibeam System of structural repair can be used to provide horizontal restraint in the external wall including BowTies and BowTie HDs to provide lateral restraint. Grouted CemTies and DryFix wall ties are used to reconnect the internal and external walls. Depending on the cause of the bowing, HeliBars can be grouted into slots (normally the mortar beds) across the crack to assist in providing simple, permanent and non-disruptive stabilization of the wall.

Common wall tie failure indicators include:

•    Horizontal cracking
•    Out of plumb, bowed, cracked or collapsed brickwork elevations
•    Rust staining on the walls
•    Problems having been identified within properties of a similar age and location

Wall ties are essential to the stability of the normally unloaded outer wythe.  The outer wythe can be affected by either direct wind forces, or more commonly wind suction forces – particularly within high rise buildings. Where insufficient or perhaps incorrect wall ties have been installed, or where the corrosion of the existing ties has been identified, then remedial wall ties will need to be installed to prevent potentially catastrophic failure.

The majority of corrosion of wall ties takes place in the outer wythe bed joint. This can lead to considerable horizontal cracking, and cumulative raising of the outer wythe.   Smaller ‘wire’ ties do not usually have sufficient corrosion product volume to crack the brickwork. Ongoing cracking is a certain indicator that new ties should be installed, and the existing either removed or isolated. In the case of ‘wire’ ties the lack of cracking will not necessarily reduce the necessity for new wall ties.

Developed by Helifix®, Inc. over many years, the patented DryFix Remedial Pinning and Tying System provides an effective, economical, and stress-free retrofit connection between all commonly used building materials. The slim profile, precision engineered DryFix helical ties (stainless steel; grade 304 or 316) are made from a drawn stainless steel manufacturing process that creates the helical hi-fin design that more than doubles the proof stress. With its’ relatively small diameter, the system provides substantial tensile properties to the concrete.

Ideal for both cavity and solid masonry constructions, the DryFix system requires no special grouts, resins, or mechanical expansion, and is embedded within the existing masonry to be fully concealed−once installed.

DryFix installation involves simple power-driving of the precision engineered, slim profile remedial ties into position via a small pilot hole. A special installation tool is then used to leave the end of the tie recessed below the outer face to allow an ‘invisible’ finish. High performance Helifix polymer grout was utilized in key areas to help increase the bond.

DryFix systems are installed into the existing masonry; expensive and time consuming tear down and rebuild were avoided while retaining the visual aesthetics of the structure.

The DryFix Tie was specified as the ideal solution for the Lancaster Leaf Tobacco Company’s structural warehouse restoration project, where approximately 6,400 DryFix helical anchor ties were used throughout key focus areas of the tobacco warehouse’s north, south, and west elevations. You can view this project and many others, by visiting our case studies section. Click here.

Key characteristics

• Non-shrink grout  which exhibits excellent thixotropic properties
• Flows easily under pressure to fill voids
• Rapidly develops compressive strength
• Cures to 6525psi
• Ready-to-mix components supplied in two-pack sets to reduce waste

HeliBond is suitable for bonding HeliBars into most common masonry-type substrates, including brick, stone, pre-cast concrete and Aircrete blocks.

Frequently asked questions

Does HeliBond grout create hard spots in a building?

Only a very low cross sectional area of HeliBond is typically required, and the HeliBars are flexible. This will allow normal building movements to be readily accommodated. So while being effective in tension, the usage of HeliBond Grout will not create stiff elements within the masonry with the potential to cause damage.

Is HeliBond suitable to use with lime mortar masonry?

Yes it is, HeliBond works differently to most common hard cementitious grouts. HeliBond is applied as a thin layer, with the ability to micro-crack, providing high tensile reinforcement to strengthen low compressive strength lime mortar masonry, while not stiffening it.

Why is HeliBond thixotropic?

HeliBond grout has been formulated to be readily injectible, while also holding its form on reaching the location that it is being injected to. HeliBond has a low liquid to powder ratio creating a thixotropic grout that avoids wastage and eliminates issues with slumping of the material prior to curing.

Can I use any applicator gun?

HeliBond should be injected with an applicator with a re-usable cartridge. Helifix sells a Crack Stitching Gun, and a Heavy Duty Gun suitable for Crack Stitching and CemTies. It is mixed using a power mixer in the supplied bucket and then transferred into the cartridge. When used for Crack Stitching the applicator must have a nozzle suitable for reaching into the relevant bed joint height. When using CemTies the Heavy Duty Gun should be used and appropriate Pinning Nozzle manufactured by Helifix will be required. Helifix also sell 4mm and 9.5mm wide Mortar Nozzles for use with their guns for Crack Stitching.

How do I clean my tools after using HeliBond grout?

Immediately after use, always clean all tools, mixers and containers with fresh clean water. Ensure that no grout remains within the mechanism. A spherical (toilet) brush is useful for cleaning the barrel and around the mechanism. If the pail is to be used more than once ensure that the pail is completely clean before loading fresh material.

When can I re point after installing HeliBars and grout?

Re-pointing may be undertaken immediately, although ideally the HeliBond should be recessed adequately below the surface and left for a few hours to start to ‘skin’ before re-pointing.

How much coverage can I achieve with HeliBond?

HeliBond is supplied packed in a pail containing two-packs of dry powder and two packs of liquid ready for mixing as a “set”. The formulation includes an expansion agent, to compensate for normal cement hydration shrinkage, to maintain a tight bond in its hardened state. A 3 Litre tub of HeliBond Grout provides enough coverage for approximately 35 linear feet (2 beads of grout) of single HeliBar Crack Stitching.

Visit our YouTube Channel to see a live installation of Crack Stitching and how to mix HeliBond Grout.

 The Helifix Group with operations in USA, Europe, Australia and New Zealand, strengthens CRH’s position in these key territories, while for Helifix this change of ownership will allow local entrepreneurship to benefit from large company resources.
Brian Barnes, Vice President of Sales, said,

“This is fantastic news which brings immediate operating benefits and secures the long-term development of the business. We are now an integral part of an international construction group that is committed to supporting our growth plans and will ensure we reach our full potential.”

“I’m delighted that this process is now complete and that the business can move forward with renewed vigour and heightened optimism.”

The existing Helifix management remains in place and, despite talk of exciting future plans, company founder and UK Managing Director Bob Paterson confirms the current focus is unchanged.

“Our customers can be assured that it is ‘business as usual’ at our operations worldwide. The immediate priority for the Helifix team is to continue to provide the high quality products, technical support and excellent customer service that the market has come to expect from us”.

CRH has a turnover of circa €18 billion and employs over 75,000 people at 3,600 locations worldwide. The Helifix Group will join the existing Engineered Accessories division of CRH that comprises a number of other market-leading manufacturers.

As expected from a major international group, being part of CRH will bring enhanced focus and continual investment in health and safety, innovation and sustainability.

New Helifix company and technical literature will be available shortly.