History in brief 

It is common to find that homes built within the 20th century (and latter 19th century) have  a “cavity wall” rather than  a solid wall. The cavity wall consists of two leaves of brickwork both a single brick deep, with a cavity in-between. These walls were not only more cost effective to build but also warmer and drier than the old solid walls. To ensure stability, wall ties were incorporated into the build. These effectively tied the two walls together.

Problems

These ties were usually made from mild steel and painted or galvanised for protection against corrosion. The problem is that this protection has simply failed to be sufficient to guard against corrosion. Homes with cavity walls built prior to the 1980's may be at risk.

If these ties start to corrode a number of things start to happen. As mild steel corrodes it can expand to many times it's original thickness and can cause cracking to render damage to mortar beds and bricks.

As the tie corrodes further, it can snap and the outer wall is no longer stable. This can cause bulges, general distortion of the outer wall and sometimes in extreme cases, sudden collapse (particularly at times of high wind).

It is quite common to find that a wall that has previously displayed this fault may have been re-pointed or re-rendered in the false belief that this will cure the cracking problem. Although these may both help prolong the life of the ties in some way, the root cause will still remain and the new pointing  or render will have to be drilled through in order to complete the appropriate remedial treatment.

Study photos

Images – Top left Advanced lifting /  Bottom left– Mild cracking / Middle – severe lifting / Right – Boundary between two rendered properties. The left hand property has had render “repaired” and has the positions of the existing ties marked on the wall. The right hand property has been left untouched. See how the cracking corresponds to the location of the existing (corroding) ties that are marked.

N.B. Wall tie replacement is often much cheaper per square metre than re-pointing. The pointing has often failed largely around the areas of the corroded wall ties and therefore will be made good in the tie installation. If you are planning to re-point or re-render your property, it may be worth having a wall tie inspection first to help with your planning. If you co-ordinate these works you will avoid having to pay for making good twice, so I can reduce the cost accordingly, as less labour is needed to complete the work!

Installation
Your home can have replacement stainless steel wall ties installed on the problem elevations and to prevent further damage from corrosion (by the original ties) the old ties are located and then treated (usually by dis-engaging from the outer leaf). Both the installation of new ties and treatment of the old ones are to the specifications detailed in Building Research Establishment (BRE) Digests 329 / 401.

Tip:- There are many different ties available and it is the installers' job to select the appropriate remedial tie for each job. The important point to note is that the job (when finished) should be able to be warrantable by the Wall Ties Installers' Federation. The warranty covers the complete job, that means the new ties themselves, the selection of the appropriate type of tie, the correct installation of the tie, the treatment of the old ties, the making good of the works and any damaged caused due to any part of the installation failing to perform the task for which it was intended.

Finishing / Making good
After the installation process the entry and exit holes are repaired using an appropriate mortar mix.

I strongly believe that however good the mechanics of an installation may be, the quality of the job will be judged on the quality of finish. I believe that it is important to discuss the finish required before the order is placed. Please look at some of the study photos below.

Brick Faced Properties
A variety of cement colours can be added to the mortar in order to ensure that the tie holes blend in with the existing brickwork.

Pebble Dashed Properties
A variety of different aggregates can be sourced in order to match the existing pebble-dash and cement colours can be added to the repair mortar in order to ensure that the tie holes blend in with the existing brickwork. Sometimes, the pebble-dash is in such poor condition that it is not possible for a good match to be made.

Painted Properties
Mortar holes are repaired however, redecoration will be required after the installation. We will be happy to arrange for these works to be carried out by a recommended contractor if requested.

N.B. As the installer, it is my obligation to select the correct ties and have found that many customers have been troubled by the choice of ties on the market, methods of installation and other details.

Here is my solution. It is my obligation to get everything right to produce the end result. This end result should be that when finished, the job looks good, it has been reasonably priced, it is ready to receive an independent secure warranty whether one is taken or not and that the customer is happy. Simple!

Study Photos

                          
Top Left – new wall ties installed old ties disengaged and all brickwork made good. Please note the top right of this photo where the installation has been made good on the render, but not yet painted. Top centre – brick / pebble dash after making good. If you look carefully you can just see the installation. Top right – The house on the right of the photo has just had the installation completed on the side. At this point it still needed to be painted but the front was tied and then painted the year before. Please note how discrete the installation is.