Wall Ties

[MdB]

The end walls of our house are of 1850s rubble and mud construction and are not in fantastic nick. The stone is the worst possible sandstone and there isn't enough mud holding it together. Looking around neighbouring properties there are signs of failures everywhere and due to the differing construction styles, I would guess that one or other of our walls fell down at some point. The wall I'm working on at the moment is top heavy (50% 300mm, 50% 600mm thick at the bottom, all 600mm thick at the top) and is of course clad on both sides with cement. As is common (I believe) with walls like this, the wall is faced on either side with the better stone with the centre being filled with rubble. Unfortunately there is some signs of the two layers delaminating with a bit of a bulge on the outside though this may due to the results of the chimney being mucked about in the past. Due to the layer of cement on the outside, I can't tell.

This afternoons job was to remove the woodchip wallpaper from the inside of the wall upstairs. It is somewhat satisfying to remove woodchip with a hammer and bolster.

I've now exposed some of the stone.

Note how well the cement has stuck to the stone (it hasn't and basically peeled off though it was hard work as it was thick. At least there is some advantage of having such rubbish stone.)

In various sections there are large voids between the stones as can be seen here:

The crowbar is 450mm long so the void goes most of the way through the wall. (I'm quietly proud of the fact that I've managed to break a crowbar...)

As I have done elsewhere, the plan is to clean the wall up and repoint in lime rather than mud. I will also attempt to fill in as much of the voids as I can so as to attempt to tie the different parts together. Lime is awful in tension so I was thinking it would be sensible to reinforce it with stainless steel wall ties and stainless steel rods / nuts and washers where possible.

Can anybody see any problems with doing this or have a better idea? Currently I don't have easy access to the other side of the wall so ideas that require this, though welcome, would have to wait a while.

In the longer term, we want to build an extension on the other side of this wall which I intend to design so it also acts as a large buttress for this wall but that is a while off. In the mean time is seems sensible to reinforce whilst I have the chance. All comments very welcome.

 

[Flyfisher]

We used helifix bars to bind some walls, but that was along their length rather than through the wall itself. But we also have some rubble walls that show signs of the delamination you describe, so I'm interested in the problem. I'm certainly no expert but I'm not sure how useful basic wall ties would be. It seems to me that they might be good at adding some tension-strength in their immediate vicinity but the structure of a rubble wall is such that it might simple continue moving around the ties. I can't see they would do any harm, but they may not be all that helpful. But I'm only guessing.

Perhaps some threaded rods and a length of steel on both sides would be a better method for holding such a failing wall together? Of course, this won't be easy if you don't have access to the other side of the wall.

Our rubble walls (originally C17 we believe) show signs of extensive repairs/rebuilding with standard bricks and I'm wondering if this might be the best structural method for dealing with such a failing wall.

 

[Penners]

I'm not sure how useful basic wall ties would be. It seems to me that they might be good at adding some tension-strength in their immediate vicinity but the structure of a rubble wall is such that it might simple continue moving around the ties. I can't see they would do any harm, but they may not be all that helpful.

I tend the FF's point-of-view on this, although I must add the same warning about my rank amateur status. I just have a feeling that, with the looseness of the wall's construction, you could find the tie bars just pulling through, in the event of the wall's movement.

Our Oxfordshire house was constructed much as your wall - two skins of fairly good Hornton stone with an infill of rubble (known, I believe, as "dross"). One of the walls had a distinct bulge to its outside skin. Being a newcomer to stone structures, I employed a well-spoken-of local builder to advise on the best repair, and to carry it out.

He simply pulled out the bulging area (leaving the sounder skin above it hanging on by skyhooks!) and rebuilt it without the bulge. He also repointed the wall. Thereafter, it was fine.

 

[Lime]

Stop thinking the modern way that everything has to be rigid and stiff and realise that old walls need to be able to move to remain standing.
Then repair with similar materials as what originally formed the wall.

 

[Feltwell]

Another vote for the FF and Penners way of thinking, that wall ties wouldn't do much. Without something against the external face on both sides to hold it together, rather like tie rods (although they usually go across the whole building), I wouldn't have thought that much could be done beyond repointing BUT I also hold the "rank amateur" status! I also think that if done badly any attempt to reinforce could make matters worse.

I would be very careful about removing the cement render - whilst it may well be the cause of the problem, it could also be what is holding it all together at the moment. I personally would opt for some careful investigation by removing some small areas of render, then seek the advice of a someone who is used to dealing with that type of construction. Do you know of a good builder locally who is used to working with traditional materials and this construction method? If not, maybe one for the "Agony Uncle" questions on here?

Highly likely that Lime is spot on, but some 3rd party reassurance from an experienced person who's seen the wall "in the flesh" would reassure me a lot!

 

[MdB]

Move is fine. Fall down is not.

Just to give you a feel for the quality of the walls around us, the other end wall has had a buttress added to it at some stage. The direct neighbour has had two buttresses added. The end wall of the house 50m away has at some stage half collapsed and has been rebuilt and there are a number of houses missing from the old maps for reasons unknown. Add to this the fact that the wall was built onto top soil rather than on to sub soil and you can see why I am worried about it.

To repair it properly to cure the delamination would require the wall to be rebuilt which isn't necessary. I just don't want it to get worse before we have chance to add the extension and buttress it properly.

I think the idea of getting somebody in with expertise in this area is a good one. I'll have a look at the SPAB site and talk to our local CO and lime suppliers to see if I can find somebody suitable. The builders we used for our previous work are great for modern construction but aren't really the right people to look into this for us.

Thanks all for the replies though.

 

[Gervase]

Rubble stone walls are tougher than you think, but if the wall is in a bad way, those brick ties would be pretty pointless. If you're seriously worried about the state of the wall, then helibars and grouting would do the job handsomely, if not cheaply.
If you're not going to be changing the loading on the wall or interfering with the ground within a metre or so, however, I'd be tempted merely to consolidate the voids by tapping in stone pinnings and gallets and then repoint.
But...
Buggering around with the ground near the wall is what is most likely to cause a collapse (and probably did so in the case of the neighbouring buildings), so if an extension is going to be built abutting the wall, with all the foundation work thus entailed, then you may wish to go down the helibar and grout road.

 

[Penners]

tapping in stone pinnings and gallets

Gervase - for the benefit of this particular ignoramus, please could explain that process a bit more?

 

[Gervase]

Pinnings* are simply loose pieces of stone smaller than your palm that you can use to push into voids, while gallets* are flatter pieces, like triangles of cheese, which serve a similar purpose. When pinning, it's best to ensure that you have stone touching stone rather than simply bedding them in mortar in the void, and to tap them home gently so they won't wiggle with finger pressure (don't do what one berk did, and whack them home with a bloody great warrington hammer and watch the surrounding stones crack and fall out of the wall. That was a handy repair job for me!). Smaller pinnings (about the size of an almond) are also useful when repointing to push into the mortar to (1) save mortar and to (2) give a more authentic finish to the repointing if the edges of the original stone have weathered, as great bands of pale mortar can look a little de trop. You'll often find masses of small pinnings if you find yourself having to rake out old lime mortar; it's a good idea to sweep up what you've raked out and riddle it through a garden sieve to salvage the pinnings for reuse.
For consolidating a tired wall like the one above, though, the pinnings are usually quite a bit larger, and some of the voids would clearly benefit from some more substantial stone held in place with pinnings and gallets.

*OED:
Pinning: [< PIN v.1 + -ING suffix1.] ...the insertion of small stones or mortar into the joints or interstices of masonry. (1533 Accts. St. John's Hosp., Canterbury (MS), To John Bryght for tyllyng and dabyng & outher pynyng xs)
Gallet: [ad. F. galet rounded pebble on the beach; also, a chip, f. OF. gal, of uncertain origin.] A chip or splinter of stone. (1712 J. JAMES tr. Le Blond's Gardening 45 The coarser Stone or Gallets.)

 

[chuckey]

I am confused, you say that the wall is 300mm (12") thick at the bottom for 50%, and 600mm (24") at the top. Is this the stone work or the render? Which side of the wall is vertical? 12" is too much to support by through bolting. Was a chimney breast removed in the 12" section, sounds as though it was, i.e. the wall is actually plumb but its got a bit missing from its lower centre section. Therein lies your solution. Rebuild the missing section, I would use 6" building blocks of the old chimney breast "foundation" or use bricks if you prefer. Do not dig the foundations out at all just uncover the top 3" of any buried stones and work off them.This could be a tricky task. Sprinkle wall ties about to bond the new bit into the old bit. Use lime mortar. The natural way the wall would go is towards the thickened top, so if this is on the "your" side of the wall, your new bit will actually be acting as a column to hold it up. Should also make plastering the wall easier.
Frank

 

[Penners]

Many thanks for that comprehensive explanation, Gervase. I reckon the day isn't wasted if I've learned something!

 

[MdB]

This is the same wall downstairs. Sorry it isn't a great picture.

The wall at the two alcoves eitherside and the chimney itself are only 300mm thick with the rest 600mm thick. Across the top of the alcoves are some hefty wooden beams which are in generally good nick and then the wall above is 600mm thick for the full width. A bit of an unusual construction. The other end wall is completely different.

As the downstairs part of the wall is so thin and pretty much all exposed, I can see that is not too bad a condition and I'm not worried about it. It is the top thicker section which I am more worried about purely from the delamination issue.

I think I am probably worrying too much about it but for my own piece of mind, I'll have a look at getting an expert in to give it a once over now it is partially exposed. We will see how much they would charge though first.

 

[MdB]

tapping in stone pinnings and gallets

Gervase - for the benefit of this particular ignoramus, please could explain that process a bit more?

Thanks Penner, I was going to ask exactly the same.

Thank you too Gervase for the explaination.

 

[Ushy M]

We have two walls with significant bowing or exposed voids, so this subject is of interest to us too. We consulted a historic buidings surveyor (sourced from this site) while the house was being re-thatched so he could see the top of one of the bowing walls, and apart from repointing with lime rather than cement (which we were doing anyway), he suggested a process of hydraulic grouting to stabilise the rubble infill (there's an old thread on this somewhere, that I think Lime and/or Gervase contributed to).

The picture below shows the inside of our gable end wall, which as you can see has been progressively extended in the past (left side) and has some infilled repairs (purpose unknown). We've already hydraulically grouted and repointed from the outside and will use the same technique on the inside - basically this means testing for voids by using a long drill (unless the voids are already obvious). Once a void is located through the mortar course, you open the hole out to about 18mm with a larger bit - this size allows you to insert a hosepipe for the lime slurry fill. Before you get to this stage, you repoint the wall externally (so the slurry doesn't fall out) and work up from the bottom grouting in approx 500mm lifts (or less if the voids are very large - we had one or two that consumed several buckets of mix :shock: ). A reasonable amount of time for setting needs to be allowed between lifts.

On the advice of the surveyor, we used NHL for this, because it is an external wall, we're high up and facing north and we were doing the work in February so a chemical set was needed. We used 3:1 (sand:lime) mix but experimentation with the amount of water is needed to get the right soupy consistency. We used dowel plugs when repointing to mark the holes prevously drilled - these can also be used as a guide for when the slurry reaches the right level, as it will start to fall out.

Suggest there's nothing to lose by trying this approach and it could result in a permanent repair.

PS with the modern plaster removed, it's now clear that the house has been re-fronted at some time and the front wall isn't tied into the gables, :shock: so this explains some of the bowing. We'll have to have to bond the two together somehow.

 

[Ushy M]

Here's one of the threads on this:

http://periodproperty.co.uk/forum/viewtopic.php?f=1&t=8448&start=0&hilit=hydraulic+grouting

 

[MdB]

Hydraulic grouting is something I have heard of before but I can't say I know much about it nor had I thought about it for this wall so thanks for bringing up the subject.

Is it this simple? http://periodproperty.co.uk/forum/viewtopic.php?p=75417#p75417

where, after pointing the crack/fissure to a depth of say 25mm, you work up the wall in lifts of say 750mm pouring in a lime/pozzalanic grout via funnel and hosepipe to the top of the section.... point up the next lift and start again.... leaving a day inbetween each section or lift. pressure grouting is too extreme and can blow the face. tried and tested. i did my complete house in this way.... used approx 400 litres of grout (hydrated non hydraulic lime and brick dust, 1 part to 5 parts of water.

I can't find anything particularly useful online. Has anybody any comments on doing it and suitable mixes?

 

[Ushy M]

MdB - finally re-found this link which we found useful when we did our grouting. Have also dug about in the attic and found the hard copy method statement the historic building chappie gave us - we have no scanner so PM me if you'd like me to bung a hard copy in the post. Hope this helps.

http://www.magenta-conservation.co.uk/technical.htm#grouting

 

[MdB]

Hi Ushy M, thank you very much for that link. Very useful. If at all possible it would be great to have sight of your paper document at well. The more information the better. If you have a digital camera then a photograph is often quick easy alternative to a scan. I've sent you a PM with my contact details.

Thanks again for looking into this for me.

I have one problem with the grouting method at the moment in that there is a chimney through the middle of the wall. The chimney is very much linked to the voids in the wall as there are smoke stains everywhere so if we grouted now we would just fill up the chimney....

I guess the ideal solution is to first fix the chimney. Unfortunately this needs to be done from the outside as that is where it has been mucked about in the past. To get access will require the removal of the garage roof (something we are planning on doing) and a tower hired. Sounds like a summer job to me which suggests leaving the cement on the inside of the wall for the time being and then thinking about it later. However, if we finish off the rest of the room now (new render, new floor, repaint etc) then the likelyhood of us wanting all the mess and disruption of removing the cement at a later date is low. This means it will never get done which isn't what I would like.

I think some careful planning and thought is needed.

 

[Ushy M]

FIne - wIll put paper document in the post. As you could see from the pic we posted, we've taken the cement off our offending wall with a view to letting it dry out over a period of months. The wall is very thick (there may have been another building attached to ours at one stage so wall is effectively double thickness) so we've left it bare since last summer. It is difficult, as you say, to plan everything into a proper - and workable - order, especially when taking into account new floors, ceilings etc as well. We've decided to tackle the wall first, as the room above is just as bad, then replace hardboard/plasterboard ceilings and floors and finally the floor.

 

[Roger H]

Well, if you do put in a big wall tie/tie rod, get a photo of it up on http://www.flickr.com/groups/world_of_wall_ties/

Once you start seeing them, they are everywhere.