Don’t get tied up in knots: wall tie surveys done the right way

We received an instruction to undertake a pre-purchase inspection of a property, part of which was to include an inspection of the wall ties. The lender had refused to accept the previous survey, which had been arranged by the estate agent free of charge, the client sent Olympic Construction a copy of the free survey report, consisting of three pages including the cover and quotation.

The property was a standard two storey semi-detached house, constructed around 1950, the external elevations made up of 275mm cavity brick walls under a hipped roof construction.

The content of the report informed that the surveyor had undertaken a visual inspection of the walls ties within the cavity using an endoscope, they were found to be in a corroded condition and a new wall tie installation was required, with no further detail relating to the property or works included.

Installing remedial wall ties has limitations

It will not correct any movement which has occurred due to failure of the wall ties and it will not remove or correct movement due to other forces or defects which are acting on the property. It is also important to remember the forces now affecting the wall following the movement are different from those which were initially considered when the property was constructed.

What the “free report” missed

When undertaking the visual appraisal of the property, the following points were clearly evident, but they had not been included within the previous ”free report” arranged by the estate agent, which all have a bearing on the structure and the new wall tie installation:

• Retrofit cavity wall insulation was installed, which will limit the inspection, there was no evidence of a drill hole to the outer leaf to allow an endoscope inspection, so how had the surveyor inspected the wall ties?
• There was a distinctive deflection to the central area of the gable elevation, although the front and rear corners were plumb.
• The original bedding mortar was black ash based.
• Raking cracks were evident to the brickwork above the two ground floor window openings.
• There was no evidence to indicate movement within the foundations.
• There was no visible lifting of the mortar beds.
• An inspection to the internal of the property found the stairs to run along the gable elevation, the stairs/ landing having a distinctive slope towards the gable. However, there was no evidence of internal cracking to the plaster or stair stringer.
• An inspection to the roof void found the ceiling joints to run front to rear and the hip rafters fixed to a wall plate on the inner leaf, with no lateral restraint installed.

 The findings

From the findings, it was evident the property was affected by ‘roof spread’. This occurs when the downward pressure from the weight of the roof covering and other forces (i.e. wind or snow) loading on the rafters, resulting in increased pressure applied to the wall plate. If this is not adequately secured, it will begin to turn/ deflect, which can apply enough force to cause the wall structure itself to move. As the roof starts moving downwards, this pushes the external walls outwards, a prolonged process that can cause severe damage to the integrity of a home.

The first signs of roof spread are often cracking, bulging, or leaning at the head of the masonry, causing bowed walls. The line of the ridge in the roof should be horizontal, movement in the structure will result in some deflection in the ridge/ hips and the rafters will show evidence of movement, sagging or bowing, pulling down the ridge with them.

At the later stages bowing in the fascia and gutter of a property will be noted, there is likely to be substantial opening at the joints between the roof timbers. Installing remedial wall ties will not address the roof spread. If this is not addressed with a correctly designed restraining system, continued pressure will be applied by the roof to the external walls, resulting in a failure of the wall tie system.

The pressure and deflection to the gable elevation has resulted in cracking to the masonry over the openings, this being quite common due to the change in the bonding at these points, these defects will also need to be corrected by undertaking Thorhelical lintel repair works, and installing lateral restraints into the first floor timbers, along with a remedial wall tie system to stabilise the external structure, or the wall will act as independent panels when affected by thermal differential movement and wind suction.

Conclusion   

It is clear the last surveyor/ report had not highlighted the structural defects to the client, and was merely installing remedial wall ties to the external elevations, without undertaking the required remedial works to stabilise the roof. The external cracking would have resulted in the continued movement of the external wall and in the longer term, the structure would have to be taken down and reconstructed, resulting in additional expense and disruption.

It pays to undertake some research before instructing an inspection, a free survey instructed by an estate agent should have started the alarm bells - who can afford to work for free and want to take on the liability?

The fact is, estate agents work for the ‘Seller’ and themselves and are more interested in completing the sale as fast and trouble free as possible, at the highest price to improve their fee. They have no interest in advising or looking after the interest of the buyer - no matter how friendly or helpful they appear to be.

It is up to the buyer to be vigilant, buying a property is likely to be the most expensive purchase you will ever make, so why would you not instruct qualified professional surveyor to undertake the inspections? It is in your own interest to pay for a survey - a small price to pay to prevent you purchasing a property with structural defects.