Extension subsidence

virb

Hello,

I hope someone can recommend the best way to deal with my problem.

I have an old brick extension which was built n years ago and only this year I noticed that the extension has slightly moved. This movement caused a gap/crack where the joint is between the house and extension walls.

IMHO Part of the reason why it moved was the pergola (built 2 years ago) which was covering 1/3 of the extension roof and due to draught this summer it settled down quite a lot and pushed the extension a little bit down (pergola was sitting on top of the extension). Currently I have fixed the issue with pergola and there’s now a decent gap between the pergola and the extension roof. This I hope should stop any further movement.

Some photos:

View from outside (neighbor side)

View from outside (my side)

The suspect (sorted):

Although, I hope it will stop moving, but I’m still conscious that the foundation has been disturbed and moved independently from the house foundation and as well the joint cracked, what can lead to even more movement if I will not take any actions.

Now, currently I filled the crack from the inside with CT1 (I know, but it got windy inside..) and will keep monitoring it to understand if it’s still moving. 

I’m aware that I have few options to fill in the crack 

·         CT1

·         Mortar repair cement

·         Expanding foam

Anything else?

I would like to hear your opinion about the best solution for my problem. I don’t think I can afford to call an engineer/specialist to investigate it and I’m not even sure if it’s worth it. Also, just to be clear, I’m not going to call my insurance to claim the subsidence for obvious reasons.

Let me know what you think.

Thank you

MikeJXE

Looks to me as the extension foundation has sunk, not properly joined to the house foundation, I'm sure thats not uncommon, theres not a lot you can do about it, no way of jacking it back up. I would suggest a good sealant on the joint and hope for the best 

grumbler

I don't believe that this can have anything to do with the pergola.

Most likely it's just inadequate foundation. Whatever you use to fill the gap, it cannot stop it growing. That's why until it stops growing, IMO it's better to use materials that are easy to remove and add. In this respect, I think, expanding foam is better. If at some point in the future you see that subsidence stops, you can remove the foam and repair the crack properly, e.g. with mortar.

stuart45

Do you know what the sub soil is? eg. clay or chalk?

Nearlyold

My wife has a near identical issue on one of her properties with an extension where a small gap has appeared between the old and the new walls - there are no step cracks in the walls themselves.

Her surveyor son has had a look and says basically not much you can do other than fill the gap with something flexible and keep an eye on the situation

His view is you have essentially two individual structures on separate foundations (in red clay in this case) that are moving slightly differently relative to each other as they're not strongly tied together, the exceptionally dry weather not helping too.

Conclusion was not to worry unduly (for the moment!)