Wall Tie Corrosion Levels
(BRE 401 Reference Chart) Description of Condition.
1. Zinc uncorroded - Zinc/bitumen layer still shiny. Spangles (zones of different crystal orientation) may be visible.
2. Zinc light corrosion - Zinc layer of even light grey colour but no shine. (Bitumen: even black colour but no shine.)
3. Zinc moderate corrosion - Zinc layer of medium grey colour with some variation (lighter or darker areas).
4. Zinc heavy corrosion - Zinc layer dark grey to black matt colour; may show some pitting or minor rust spots.
5. Zinc white rust - Zinc covered with a white compound; may show some pitting or minor rust spots.
6. Zinc terminal corrosion - Zinc corroded, and up to 10% of the area has red rust, but the tie cross-section is not reduced.
7. Red rusting - Zinc substantially gone; large areas of red rust, but cross-section is not significantly reduced.
8. Red rusting & erosion - Largely red rust with build-up of iron oxide layers and significant loss of steel cross-section.
9. Total failure - Steel cross-section is less than one-third of the designed cross-section, or completely eroded.
Note
Bitumen paint films have often been used as a substitute for zinc protection in times of shortage.
These may be judged roughly using references 1, 2, 4, 6, 7, 8, 9 by substituting "Paint film" for "Zinc".
Quantitative measurements would be meaningless.
How much is a wall tie survey?
At Surveying Wall Ties, we offer a fixed-price wall tie survey for £250.00. This includes a professional inspection and a detailed report, with no hidden charges or obligation for remedial work.
Who can check wall ties?
If you suspect an issue with your wall ties, you must seek advice from a specialist wall tie surveyor who can provide a thorough and unbiased assessment. I am an independent surveyor and I do not offer a replacement service.
How serious is wall tie failure?
Wall tie failure can be extremely serious, sometimes leading to the collapse of the outer leaf of the wall if left untreated. Early identification and action are vital to maintain structural safety.
How do you test wall ties?
Testing wall ties typically involves a visual inspection and the use of a borescope camera to examine the cavity wall without causing damage. A surveyor may also take small samples for laboratory analysis if needed.
Can wall ties cause damp?
Yes, failing wall ties can contribute to damp problems. Moisture can bridge through defective ties or gaps in mortar, leading to penetrating damp inside your property.
Can I replace wall ties myself?
DIY wall tie replacement is not recommended. It requires specialised equipment, experience, and a clear understanding of structural loads. Always consult a qualified professional.
Do all houses have wall ties?
Wall ties are present only in cavity wall constructions.
What does wall tie failure look like?
Signs of wall tie failure include horizontal cracks in the mortar joints, bulging brickwork, and misaligned rows of bricks where the outer wall starts to separate from the structure.
The Wall Tie Survey is straightforward and usually takes about two hours.
Upon arrival on site the suyeyor will introduce himself to the owner and carry out a visual inspection of all elevations.
Having done this he will use a metal detector to locate the positions of the Wall Ties on each elevation then drill a 11 mm hole in the motar bed near the ties.
Using a boroscope to view the ties, photos will be taken.
After the survey, all holes will be made good.
We use the Building Research Establishment (BRE) Digest 401 how to visually grade existing Wall Ties to grade your property.
The BRE 401 sets out nine classes of Wall Tie Corrosion ranging from no.1 bright not corroded to no.9 very rusty or totally failed. See below.
Our surveys are carried out for the fixed price of £250.00