Solutions for Restraining Movement in Walls

[johnobirches]

Hi again,

To get a mortgage for our new old house, we had to have a structural survey - fair enough.

The surveyor pointed out some cracks and evidence of outward movement of the front wall away from the cross walls on the first floor (upstairs).

This is backed up by obvious cracks once we got the plaster off. See pics of before and after I raked out the joints.




I'm going to work my way up this crack removing stones and mortaring in new stones to both walls which overlap at the corner (using lime mortar by the way).

The structural surveyor pointed out in his report that the movement may have been very old and that lime mortar remains relatively soft and allows movement but then went on to recommend the fixing of L shaped metal straps up the inside of the corners where crosswalls and gables meet front and rear walls and also the fitting of L shaped metal straps at 1 metre spacing along the tops of 1st floor joists and up the face of internal walls.
We may be required by our mortgage lender to show that this has been carried out but I can't for the life of me see how I can get solid enough fixings into these rubble walls to make such a solution effective. The stones are too small to drill and in any case any drilling would just loosen them, and trying to secure fastenings into the lime mortar between stones would just be silly.

All I can think of doing is installing some of those cast iron plates on the front and rear outside walls which are joined by a long rod passing throught the whole house. [Anyone know what they are called and where to get them?]

Any other suggestions would be appreciated. The daft thing is that from the outside there is no noticable bulging or spreading of the walls.

We hope to make the upstairs ceilings vaulted which will have implications re: possible spreading of the upper exterior walls but maybe we could make that part of the solution. - Another topic required there though I think.
Cheers
John

 

[robgil]

I had an internal clay lump wall that had not been fixed into the external, if tou can imagine a 'T' with the top horizontal line being the external wall. The internal wall (vertical line) was wobbling around like nobodys business. I sank some steel pins into the internal wall that went on into the external as well then lime mortered over the holes.
It was'nt ideal but the wall is quite stable now.
The fixings dont need to be over engineered, if it were me I would put steel straps on and fill the corner with lime mortar, especially if the movement is historic. Less is sometimes better.

 

[Roger H]

No idea on the solution to the issue but the ties you describe are called 'pattress plates' (sometimes wall ties).

 

[robgil]

Looking at your pics again it doesnt look like movement to me , it looks more like water damage. It isnt a crack, more the mortar between the stones has gone missing.

My extension was diagnosed as subsidence however the crack in question was due to the external door not having a lintle and it cracked as a result, sometimes they do get it wrong and it might be an idea to get a builder to look at it and give you their view on what is going on.

 

[Lime]

There is a world of difference between new and very old movement.
I'd want to know if it is moving or not personally.
An old method would have been to use strips of glass bonded across the gap and wait.
It doesn't look bad at all to me if it is old movement.
... it could be water damage as robgil suggests too, it is very clean.

Unfortunately you have removed perhaps the most tell-tale internal structual part of the problem, the plaster, and made the "problem" unable to be overlooked.

Fitting T and L shaped straps will be almost impossible as you say and probably pointless too.

 

[johnobirches]

Ah Pattress Plates! Thanks. Have found http://www.redgwick.co.uk/ who look very useful.

Could be water damage as there were some big voids in the mortar and lots of old black organic debris (mice or spiders?) but there's no sign of washout debris or marks on the boards or downstairs.
The structural surveyor noted the problem before we bought the property as the wallpaper (very old) was also stretched and cracked. We then had to remove the plaster to see what we were dealing with.
The crack looks bigger now and clean because I have raked out the joints and brushed away all the loose mortar. I'm wondering if the movement occurred when the house was re-roofed {late 20th century I guess} and the roof pitch reduced from the days when it was probably thatched.

Just this afternoon I have contacted a local structural engineer who specialises in old buildings I'll report back on what he says.

Thanks to all for your replies - several heads have got to be better than one and it's so easy to get stuck and not know what to do next for the best.
Cheers
John

 

[robgil]

John were any internal walls removed? Or any structural repairs done at any time?

 

[middi]

Google " HELIFIX".

Middi

 

[robgil]

Thats exactly how I did mine, without the 185 quid price tag. :shock:

 

[chuckey]

The internal corners of rock and rubble houses are extremely weak, due to the bonding across the corners being done with non flat stones. Imagine bonding a corner with bars of soap! The external corners are bonded with quoins so have a decent flat surface "going round the corner". Try digging out the mortar courses around the corners and bond in bent stainless steel bars. (I used reinforcing bars designed for internal glass block walls).
If you want wall to wall tie rods, use steel re-bars for concrete with a bit of studding welded at each end. the problem I see with this system is distributing the stiffness of the tie across a decent area of the outside blockwork in an attractive way (do they still make those big Xs?)
Frank

 

[MdB]

I've been looking for a suitable place to purchase helical bar and these are the cheapest I've found.
http://www.permagard.co.uk/crack-stitching.html

 

[MdB]

From here: http://www.tritonsystems.co.uk/prodc1.php#p6

Triton Lateral Restraint

Typically used to stabilize old or bowed walls, Triton’s Lateral Restraints are manufactured from 8mm diameter 304 austenitic Stainless Steel rods. They are available in a standard 1m length but can be supplied in other lengths on request. They are designed to restrain the whole of the brick outer structure to the floor joists. Installation involves minimal disturbance to the homeowner as they are fitted from the outside of the property.

Supplied in 400ml cartridges.

:shock: :roll:

 

[Andrew Bodenham]

johnobirches,

I'm glad that you've consulted a structural engineer. There could be many causes for the movement which has occured, and it will be necessary to determine if the movement has stabilised or is still occurring. Only then can a suitable plan of intervention be proposed - which may be 'do nothing'. Too often people jump to conclusions and start applying remedial treatments to properties before the nature of the defect is fully understood. Diagnosis first, then treatment.

Let us know what is discovered.

 

[johnobirches]

Thanks again folks for all the responses and links - now can talk to the structural engineer in a more informed way.

Chuckey - too true the walls are built of field or river stones the shape and size of turnips! When I've marvelled at the construction people have said "well these places were built by farmers not builders" which I suppose is true but farmers knew how to build dry stone walls all those years ago and that joints need crossing and wall junctions need tying in. I'm quite surprised they didn't apply the same techniques to mortared walls.

Anyhoo I will check out the various links and suggestions and then report back when I've spoken to the engineer.

Goodnight from soggy Lancashire.
John

 

[88v8]

I agree that it should have tell-tales fixed across the cracks, preferably the variety with a scale you can plot monthly on a graph. Then leave it for a year to see if there's any movement, and whether the movement is just seasonal.
http://www.surveyexpress.co.uk/Home-Inspection/Crack-Monitoring/c-1-131-142/?gclid=CIDl-p325rICFQfKtAodxXIACQ

Trying to fix anything to walls such as this is difficult, the idea of making structural fixings is comical.

If you eventually decide to insert tie rods from front to back of the building, you have to be sure the back walls will accept the load of course.

Ivor

 

[MatthewC]

The crack looks bigger now and clean because I have raked out the joints and brushed away all the loose mortar.

You want to be very careful doing that with lime mortar as you could go on for ever!

The structural surveyor pointed out in his report that the movement may have been very old and that lime mortar remains relatively soft and allows movement but then went on to recommend the fixing of L shaped metal straps up the inside of the corners where crosswalls and gables meet front and rear walls and also the fitting of L shaped metal straps at 1 metre spacing along the tops of 1st floor joists and up the face of internal walls.
We may be required by our mortgage lender to show that this has been carried out ...

I found large cracks when I removed old lime plaster but I could prove from my initial photos that there had been nothing major visible, or possibly only a very small crack in places. Hence the "structural crack" was a very old defect (possibly from inital build) and so I just filled and re-plastered.

Does your mortgage have any condition relating to this "defect"? Even if there is, in my experience they are quite unlikely to follow up this sort of thing, unless there's a retention. If there's no condition or retention then do what you want, not what the surveyor suggests. I'd be very cautious about doing anything within a couple of years; just see if there's any movement over a year or more and go from there.

Matthew

 

[johnobirches]

Thanks Matthew, - I have had a similar thought - that no-one is likely to check from the mortgage company that the work has been done.

The meeting with with the structural engineer left me feeling a bit confused and frustrated. His CV says he's a specialist in old buildings and he was very pleased that I was intending to use lime and keep things breathable...
BUT he suggested using right angle steel straps across the crack (even though he thought it wasn't too serious) when I said the stones were too small to drill he said to anchor the fastenings in the lime mortar joints with resin - just can't see how this would work unless I used masses of resin.
The big thing was that he 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.
We need a structural eng to do the calcs for the beams supporting the new openings we need to make and need an architect to do the construction detail drawings for the new extension and refurb hence our going out to the professionals but at the moment I feel I could use some empathy... glad the forum is here!
John

 

[Keithj]

A "rising damp" expert, i'faith!

I would be very tempted to get a second opinion from a different techie person.

 

[88v8]

How old is he?
A dpm will appear to work, for a while, it may take years before the damp appears in the walls. We took out a 1972 dpm/cement screed in a room where the damp around the perimeter had become so severe it had rotted the Gripperods that anchored the fitted carpet - yes, that got thrown away too.
Many 'experts' spend a lifetime defending the dogmas of their youth, and your 'expert' might be retired before the result of his bad advice becomes apparent.

After all, in 1986 Hugh Lander was so casual about dpms that he makes no attempt at all to justify them, to him it seems they were a routine response to damp. He also used gypsum plaster and cement. And yet, at the time, he was a respected expert on correct restoration.
Much of the building trade is still in 1972, or 1986, and if you want a sympathetic hearing for a lime-based solution, I'd contact Ty Mawr and ask them to suggest some experts who are accustomed to working with lime.

I'm quite sure however that trying to tie rubble/lime walls together with resin and angle brackets is just barmy. As I suggested, put tell-tales over the 'cracks', plot the results on a graph or in a spreadsheet for a year and then think about it again. The solution could well be - do nothing.

Ivor

 

[johnobirches]

Thanks for the wise words Ivor.
John