Repairs: walls

Bowing and distortion to walls can occur for a variety of reasons:

• overloading of the wall because of modern concrete tiles being used on the roof instead of slate (as per the original specification), upsetting the equilibrium of a building that was otherwise previously performing satisfactorily;
• lack of adequate restraint and bracing to the wall;
• collapsing arches over windows or doorways;
• soft spots in the ground where the foundations have inadequate bearing so that the wall may have rotated slightly on the foundation causing bulging further up the structure as it deforms;
• poor original building materials;
• ‘external influences’ such as shockwave damage from Second World War or other bombing incidents;
• solar overheating of a wall without expansion joints.

Solution 1

If the problem is caused by solar overheating, a solar reflective or light toned paint may assist if the problem is slight.

In addition to any other repairs needed, it is appropriate to tie back the wall, provided the degree of distortion is within acceptable limits (extra wall ties or tie-in to the joists).

However, be aware that over-restraint elsewhere risks making the problem worse. For example, rebuilding sections of the wall using an overly strong Portland cement mix in the mortar would constrain the ability of the wall to move and might make distortions worse in weaker areas adjoining the repair.

Solution 2

Traditionally the remedy for a bowing wall is to use restraining bars or tie bars with the classic iron or steel crosses or discs acting as spreader plates visible on the external part of the wall – helping spread the load of the restraining bar, which was subsequently run over the top of the floor joists (notched into them) and fixed down beneath the floor covering.

When carrying out this type of exercise it is particularly important to ensure that adequate restraint is placed across the floor, e.g. using timber noggings so that the joists are not prone to buckling across their width.

The traditional tie bar is a useful way of restraining the wall and certainly the spreading plates across the surface of the wall can spread the point load picked up from the restraining bar over a considerable area. However, they are somewhat unsightly, and more discrete methods of restraining the wall are now available.

Solution 3

Stainless steel helical bars similar to the wall ties mentioned above can be used to stitch the wall and effectively attach it by penetrating the wall at a number of locations and spearing through the joists. Some form of nogging is essential to prevent the joists buckling and deforming sideways, but a cosmetically improved restraint can be put in place (when compared with the traditional tie bar) with significantly improved rigidity across the wall.

It is also worth considering the use of galvanised steel straps fitted across notches within the joists where they run parallel with the distorted wall and strapped over nogging pieces and screw fixed to the inside leaf of the wall which, coupled with wall tie repairs, can provide some significant additional bracing.

A variety of systems have been produced by Helifix Ltd. The figure below illustrates the range of applications.

The use of polyester resin glue is generally essential when using stainless steel helix solutions; it provides an amazing amount of adhesion in order to glue together fixings and masonry finishes.

Cost sequence - Installation of helical fixing wall anchor to secure bowing wall

• Assumes that wall anchors will be inserted at the first floor joist level.
• Contractor to supply scaffold tower or equivalent safe working access.
• Assumes that the elevation of the building being treated is not obstructed by any unusual hazards or building projections with no special access requirements resulting from this.
• Specification assumes 4 stainless steel helical anchor bars are drilled through from the external face of the wall at 1m centres.

1. Take up floorboards internally and carefully set aside for reuse.
2. Install noggings/blocking pieces to the voids between 3 sets of joists running parallel qwith the wall: 3 noggins per void (9 in total).

• Assumes that the helical tie bars will be positioned to miss any services that no rerouting of electrical or pipe work is required.
• Ensure the helical tie bars pass through the stiffened joist sections.

1. Repoint face of wall where the helical bar has been drilled through and secured with resin bonding.
2. Reinstate floorboards, screwed back down into place.

Wall anchors - COST £400

Small works pricing

Since the original price estimating in 2008 the economic turmoil of the last few years has caused some disparities in pricing - if you are reviewing these figures in the London area they may look laughable - if you are located in Hull they might still look a bit expensive. Please treat them with caution and of course always consider obtaining more than one quote against which to test prices. Reference to the BCIS or a small works pricing book such as Spons or Laxton's will help assess costs and the hourly labour rates upon which they are based.