Solutions for Restraining Movement in Walls

[FamilyWiggs]

It is certainly worth checking that this is old movement. We had a front wall of our outbuildings that wasn't tied into the cross walls at all. This was the result:

We've had it rebuilt and tied in in two ways - firstly with concrete t-bars set into the front and cross walls as they were being rebuilt and secondly (and probably not necessary) with some helical steel bars laid in as well. There is no longer a void in the wall, and so I'm reasonably confident that this will now outlive the grandkids.

One thing I was persuaded on but still have slight doubts. Our mason (well respected and carefully chosen, does work for NT, Heretics, CADW, etc) was not happy once we'd cleared the footings and dug a bit into the clay just to relay the wall in the existing footings. We excavated further and poured in some concrete, and then built the wall on that. Normally I'd have been fine with that - but we weren't rebuilding the whole front wall, so I have some misgivings that the building may pivot in future as there are differences in the footings.

However the original building has been there for 2-300 years, so I'm reasonably comfortable it has settled. I just hope the grandkids don't curse me if they have a large crack open up.

Apologies for useing the word concrete twice (now thrice!) in a post ... but I'm a firm believer that all building materials and approaches can have their appropriate place in a project - with the obvious exception of expanding foam! Mind you, even that I suppose has its use in window installation?

 

[MatthewC]

...the structural engineer ... absolutely insisted that a damp proof membrane was the way to go for floors (not because of any site specific reasons - his argument was that moisture will only come upwards in a breathable floor and would never go downwards). He simply pooh pooh'd the logic of the LECA and limecrete approach I showed him in the Old House Handbook.

He seems a bit of a liability. Thanks to a bit of previous knowledge, a Mike Wye one day course and this forum, I have proved a lot of things about how to tackle dampness in old buildings - this one is now dry and relatively warm, but for the previous owner it was a freezing damp ruin! I have also proved that LECA and limecrete works in a floor - see my blog in May 2011 (click the blue spot on the right). If you are within reach of Oxfordshire/Bucks then PM me and come and see.

Matthew

 

[chuckey]

FamilyWiggs, I think your collapse demonstrates perfectly some thing which I have postulated but never actually seen in practice. The problem I am postulating is that when some houses were built in stone, to be "posh", they lined the door and window voids with vertical stones, which also offered some support for the lintel. After 200 years the lime mortar has weathered down (or away) leaving the stones at the side of the "standing stone", loose or at least not carrying their fair share of the load. So eventually the "standing stones" , which normally have their "grain" running the wrong way, cracks, the lintel falls and the result is what happened to you.
The real problem is that there is no real cure except for rebuilding around the opening, leaving out the "standing stones".
Around here (Wensleydale) there are only a few (two?) cottages still standing with this form of construction, compared to hundreds of more conventional construction, though the problem is how many were ever built?
Frank

 

[johnobirches]

Well work continues slowly - still skirting around the major issues while we try and plot the best route ahead.

The engineer who insisted that DPM was the only way to go for floors has replied and the following is an excerpt...

The concept of a breatheable external wall and breatheable floors are quite different. In the former there is "dry" air on both sides of the wall, and in the latter there is "wet" soil on one side and a useable domestic living surface on the other.
I can't recall the breatheable floor section which you showed me, but most such sections incorporate some form of breatheable membrane with clay balls and/or limecrete.
Firstly, the clay of course becomes virtually impermeable and the "breatheable" membrane is in my opinion unlikely to remain "breatheable" in intimate contact with films of clay, lime, water, etc. on both sides. Consequently you are likely to end up eventually with a construction approaching an impermeable membrane in some form.
Secondly, and probably most importantly, the ground beneath the floor is likely to remain permanently "damp" unlike the external wall situation where the external atmosphere does at least dry out on occasions (perhaps not this Summer). Thus, moisture can only migrate in one direction, that is upwards through the floor surface. This probably works reasonably well most of the time in well drained sandy soils with a low water table, but in your case the sub-soils are most likely glacial clays with high perched water tables.

It's certainly true we are on clay and the surrounding fields are very soggy after this summer but we are on a slope and having lifted one (concrete) floor there is no excess moisture (water or sogginess) underneath. His argument seems to have a certain logic though and I am curious about his suggestion that the clay beneath and [ultimately degraded]LECA above will eventually clog the breathable membrane resulting in an impermeable floor anyway.

Any thoughts folks? Does anyone know of any study of the long term performance of these LECA Limecrete floors. I've not seen LECA yet but could it really break down into fine clay which could clog the membrane?
Thanks
John

 

[tobydog]

I'm certainly an amateur here but a Very good question on the long term efficacy of LECA. I have a bag that is about to go down in the narrow gap between the plinth and concrete floor before capping it off with lime mortar / limecrete.

The LECA shouldn't actually be in direct contact with the ground or the limecrete slab above and should be protected by two membranes. You should also use coated LECA rather than the uncoated type which can be mixed with the limecrete slab.

There looks to be a good alternative to LECA in the link below. It looks to be a more recent development but logic says that glass, foamed or otherwise, shouldn't suffer the same potential issues as clay.

http://www.lime.org.uk/products/limecrete-floor/components/recycled-foamed-glass-gravel-rfg/

 

[MatthewC]

I can't see why your chap thinks that the LECA will break down (if that's what he's saying). It is very hard stuff; it is brittle so if subjected to shock (e.g. being trodden on!) it will turn into dust and bits. Because it is the product of a firing process (in power stations?), I would expect it to last for a long time. What you have to avoid is treading on it whilst laying it - I agree that would cause fines which could block the membrane. The other key is probably how well drained is the soil around/under the house, and is the soil level well below the floor level?

He could be right that problems might occur "eventually" but I reckon that would be several hundred years, not five or twenty. Apart from the one I did last year, a large limecrete floor has just been laid in the church opposite me, and that was designed/approved by an architect who specializes in old buildings.

Speak to Mike Wye or Ty Mawr, etc and ask their advice.

 

[johnobirches]

I've booked a 2 day course at Ty Mawr so will ask loads of questions.
I appreciate your comments though.
Thanks again.
John