Should brick foundations be this badly spalled?

[Galen]

I've had problems with penetrating damp in a ground floor flat I own in a converted Victorian water mill. If you want a bit more background (and further pictures of the effected wall), please see my earlier post here:

Mystery concrete plinth, and damp problems

To try and cut a long story short, I've got some penetrating damp problems with a ground floor flat in a converted Victorian mill building. I posted about this before, so there is some additional information here...

www.periodproperty.co.uk

The management company arranged for an investigation of the foundation of said wall (with a structural engineer present) to see what could be done - there were some unusual features that they wanted to investigate (outlined in the post linked above) before implementing a solution (a french drain was a common suggestion from various people involved).

Anyway, cut to the investigation. Unfortunately I couldn't spend much time actually on site due to work commitments. But I did manage to visit briefly and take some pictures, which I've attached below.

I was pretty certain the wall would have a stepped brick foundation (and indeed it does). And I knew that it would likely be somewhat damaged from exposure to years of water ingress, freezing, etc. but I was actually quite shocked at just how damaged these foundational bricks are. Lots of them look like they've basically dissolved away over the years ...

For reference, this wall is roughly 14.3 metres (47 feet) tall, and supports 4 floors (including the ground floor), so these foundations are supporting a consierable amount of weight.

Is this normal for a solid wall property of the era? I suspect this wall is maybe 110 years old (very unlikely to be much older than 120 years old).

I haven't read the report from the structural engineer yet, and I wanted to discuss other matters in the brief time I was able to visit the site, but the more I think about this the more I'm worried that this surely can't be good?

 

[Cubist]

How far below your normal soil surface level are those footings? Normally they would be well below the typical freeze level and therefore should not be affected by the freeze/thaw cycle responsible for spalling. Also, a lot of the damage to those bricks looks very new, are you sure their faces were not damaged during the excavation work?

 

[Galen]

These footings don't appear much below ground level at all. You can see roughly where the ground level was from where the soil markings on the wall extend to (at a rough guess, I would say the distance is maybe 25-35cm from the top of the soil to the start of the footings).

I'm not sure how far below ground level you need to get before bricks can be considered protected from the freeze/thaw cycle, but they do seem quite close to ground level.

It's possible that the damage was done during the excavation yes. I'm really kicking myself that I couldn't easily arrange to be there to see it all take place (and that I didn't take more photos). But this looks like it was all done manually with a spade (no heavy machinery in sight when I was there), so I can't imagine they would have been able to do much damage to these sorts of bricks with a spade? Unless they were already in a rather fragile state?

I've attached the only other picture I took of this part - you can see some rubble off to the left. Perhaps these brick fragments had already broken away, but I suppose it is possible they were broken off while digging down.

I'll be checking in to see if there's a report I can view tomorrow. It'll be interesting to see if the structrual engineer made much of this.

 

[Cubist]

Barring for the northern parts of the nation there have been very few periods of protracted freezing conditions over the last couple of years at least and, for the most part, such conditions have been restricted to a few days of surface frost at worst. Surface frost does not penetrate very far into the ground and would definitely not reach beyond 5cm or so. Long and very hard periods of freezing conditions would be needed to reach the bricks at the bottom of those holes - but this building will have seen such in the decades since it was first built.

Water sodden bricks can be easily damaged and the typically used in footings are not usually of the highest quality. The edge of a spade or mattock could, in the hands of a thoughtless or unknowing user, easily produce the damage you're seeing there. Given that, my concern would be that repeated blows from a spade or mattock could induce shock damage to the bricks and weaken the footings structural integrity. Hopefully the surveyor will have assessed whether remedial measures are now needed.

 

[stuart45]

18 inches was always considered the maximum frost line in the UK.

 

[Galen]

Just wanted to say thank you both for your responses here.

I got the report from the surveyor/structural engineer today, and he said:

The results of trial pits 3 and 4 to the gable wall elevation revealed an original
random brick footing with a depth from existing ground level of 500mm with a
minimal projection of approximately 150mm. Again there was no indication of
any water present in the trial pits. The brick footing is founded onto the Fill and
Boulder Clay mix.

So I think he concluded that this was more or less the original state of the foundation here. Or at least, that's how I'm reading that?

I suppose at this stage there's nothing much to be done anyway. I was just surprised to see it in that state (although maybe it's not that unusual for a property of this age).