Greenhalgh & Co.

Chartered Building Surveyors & Valuers

 

boltonsurveyors.org.uk

Greenhalgh & Co.

Chartered Building Surveyors & Valuers

21 Towncroft Lane

Bolton  BL1 5EN

Tel: +44 (0)1204 845382

Mob: +44 (0)7813 439196

Email: greenhalghco@btconnect.com

 

RICS Company No. 002973

 

Ageing a crack

The presence of dust/dirt/cobwebs in cracks and their likely age 

 

We have investigated whether the presence of dust, dirt or spiders webs in cracks can give a surveyor an indication of their age, and thus he can establish whether the movement that caused the crack is historic or recent.

 

To check on the above we undertook the following:

 

  1. Used a strong light source and a magnifying glass to try and assess whether dust/dirt/cobwebs existed and their extent.

 

  1. Used a vacuum cleaner and clean damp white cloth to extract dust/dirt/cobwebs from cracks, and then checked the amount extracted.

 

We used the test on the following:

Shrinkage cracks in a blockwork wall which were fifteen years old (approx)

Shrinkage cracks in a blockwork wall which were five years old (approx)

Crack in a piece of blockwork that was 1 minute old (approx). 

 

(Note: shrinkage cracks were used because we can date them to shortly after a house was built and thus have a good indication of their age)

  

The magnifying glass

 

15 year old cracks

We could see some cobwebs (very small and random) but it was not possible to determine the amount of dust/dirt.

 

5 year old cracks

We could see some cobwebs (very small and random) but it was not possible to determine the amount of dust/dirt.

 

New crack

No cobwebs were found of course, but by the same token it was not possible to determine the amount of dust.

 

The vacuum cleaner test

A conventional vacuum cleaner with a hose was used.  A fine piece of white cloth was secured over the hose mouth and moistened.   The face of the two different blockwork walls were brushed clear of any surface dust.  The newly cracked piece of blockwork was similarly treated.  We then used the vacuum cleaner to suck out dust/dirt.

 

15 year old crack

Dust/dirt was found stuck to the moist cloth, it tended to be grainy in texture.

 

5 year old crack

Dust/dirt was found stuck to the moist cloth, it tended to be grainy in texture.

 

New crack

Dust/dirt was found stuck to the moist cloth, it tended to be grainy in texture.

 

Note: we had no success in sucking out cobwebs, or if we did we couldn’t actually see them on the cloth.

 

Conclusion:  The very process of cracking a piece of masonry [in our case blockwork] creates dust and grainy particles.  Therefore to determine the age of a crack by the presence of dust/dirt, would in our opinion be impossible for a surveyor if using visual methods or for that matter a vacuum cleaner. 

 

Even if one could show the crack had dust and dirt in it other than that created by the process of cracking, how then would one date the point at which the dirt or dust entered it?  

 

It is of course possible that there are more scientific methods of analysis which would yield a more definitive conclusion as to the age of a crack.  The possibility of dating cobwebs has potential because they are organic.  Although we know of no one who can do this. 

 

The problem we encountered with cobwebs was; some cracks simply didn’t have any, irrespective of their age.  Likely because they were unattractive to a spider, so in essence the presence of cobwebs probably relates to how attractive the crack is to a spider, as opposed to the age of the crack.

 

The only real definitive conclusion we can reach is that a new crack doesn’t have any cobwebs in it!