Pointless repointing - do hairline cracks really need it?

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The very mention of 'cracks' can strike fear into any home owner - but I think the seriousness of cracks is often grossly exaggerated.

I have some hairline cracks (mostly less than 1 mm) in the external walls of my terraced house (along with probably most of the old housing stock in London - and a fair few of the new ones I expect...). They were professionally monitored within the last 5 years and haven't increased. They have probably existed for much longer. No actual bricks are cracked - they seem a very hard type (except the lintels perhaps), not prone to spalling either.

My insurers say the cracks should be repointed. But is this really necessary? There may be a case for repointing the lintels - the red bricks are less robust. But as for the rest - it would look horrible, and be pointless in my opinion.

The house dates from about 1900 and won't be falling down any time soon. It is probably built on shallow foundations, on clay, and is about 50 metres from a tree-lined railway line. I feel that anything short of complete underpinning (not an option) is not going to prevent further movement in the future. Cracks can be remortared, with mastic as well perhaps, but at some point they will open up again, or, if they've been effectively bonded, new ones will appear elsewhere - necessitating even more pointless repointing!

However I can see there may be some benefit in preventing excessive water ingress. Is there any alternative to repointing which would limit it - clear mastic perhaps, or some form of water repellent which could be sprayed along the line of the cracks, or even injected?

 
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Just forget about them. It's our changing climate and your London clay that is causing it.
 
Yes leave them.

Or run a bit of clear silicone in them for an unobtrusive repair, and monitor over the course of a year
 
The house was probably built with traditional lime mortar. The beauty of this stuff is that is slightly plastic and will accommodate small movement without problems. Also, lime tends to be chemically 'self-healing' for small cracks, in that they eventually seal over.
My guess is that these houses have been re-pointed at some time in cement mortar, which is hard and un-yielding, and will show hairline cracks following slight movement.
As the others have said, it's not a problem.
 
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Would agree with Tony on this. Looks like a strong cement mortar was used.
It can also cause damage to softer bricks in time and damp problems. Many builders still think that a strong cement mix will last longer.
 
Thanks for all your responses. I feel I'm in the presence of people who know what they are talking about!

If I decide to have a go at filling / sealing these cracks can you recommend a particular product, or type of product? There seems to be such a vast range - would any exterior silicone sealant (if that's the best thing) do the trick, or do they vary?

I guess it would need to be clear, 'fluid' enough to penetrate narrow cracks, flexible but not shrinkable, and with good adhesion to bricks. And not too difficult to apply (from a ladder...!).

Thanks.
 
Small hairline cracks like that can't really be effectively filled.
If there is no damp problem internally, why bother? Over time, the cement-mortar pointing will start to come away in places and you will eventually need to have it re-pointed properly, using a more forgiving material. Until then, just leave it.
 

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