Bowing house wall - tie rods?

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Phil Addison wrote:

Thanks Phil, that would be much appreciated.
--
Grunff


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First of all, the house is quite different to yours. It is an 1890 end terrace built with 11" single skin brick, i.e. 2 bricks thick, no cavity. My daughter was having a loft conversion done when the builders noticed the gable wall leaning, and pointed it out 'so they wouldn't be blamed for it'. It was, like yours, firmly attached at the two end walls and bowing out from them. There some cracks visible internally.
I got a structural engineer to look at it and he reckoned it was fairly typical of that kind of property and not too bad, but he advised tie-rods to prevent further movement.
The joists are parallel to the gable wall, and the opposite wall is a party wall (being a terrace property). Apparently you don't want to fix to the opposite wall (which in our case is a party wall), but to strengthen the joists and affix the tie-rods to them. I suppose fixing to the opposite wall would risk distorting that. The following is a description of the finished work that I did, and there is an associated drawing that I could send you. Basically, 7 joists are braced together with noggins, and boarding nailed over them to make a very rigid diaphragm assembly supported on the side walls. The tie rods are fixed to the 7th joist (from the leaning gable wall) only.
Description:
"There are two tie-rods equi-spaced between two steels I-beams which are 3m apart and mortared into the walls. (These beams are nothing to do with the tie-rods; they support the floor of the loft conversion).
The tie rods consist of M16 studding inserted through 20 mm holes bored through the centre-line of 7"x2" joists, and the gable brick wall.
The joists are secured to wooden cross-members, which in turn are attached to the steel I-beams using joist hangers and nails. There is an additional roof I-beam, supported on lintels, at the apex of the gable. The rear elevation of the loft has been converted into a flat-roofed dormer room.
Each tie-rod is composed of three 1m sections of M16 studding with the outer 1m section being stainless steel and the two inboard sections being mild steel. The sections are joined using M16 mild steel couplers with lock-nuts each side.
The inboard end is restrained with a 100 x 100 mm x 10mm mild steel plate, M16 washer and a pair of lock-nuts.
The load is distributed over seven joists (2 of which are doubled) by two rows of 50 x 100 noggins per tie-rod. The noggins are staggered to allow nailing. These are in addition to a row of noggins across the centres of all the joists.
18 mm tongue and groove chipboard flooring is nailed to the joists to form a diaphragm.
The outer wall plates are stainless steel discs 300mm diameter, drilled and tapped M16 at the centre. They are screwed to the studding and each locked with an M16 nut and washer (all in stainless steel).
The external rendering has been hacked away in the area behind the discs and a thin skim of waterproof sand and cement mortar applied. The disks were carefully bedded into this to ensure even pressure on the wall. After the mortar had cured the discs were removed and frame sealant applied behind and around the periphery to make a waterproof seal, and then the discs replaced and locked. Finally the tie-rods were tensioned by tightening the inboard nuts, and the lock-nuts secured."
The trickiest part was drilling the holes through the wall from the outside so that they accurately lined up with the joist centre line. I could not drill from the inside because a joist was close to the wall, and the length of the drill bit (plus drill) was much greater than the distance between joists. I actually drilled some location holes above the joist line and worked off those. The problem there drilling horizontally accurately enough, so that there wasn't too much vertical error between the start and finish of the alignment hole.
The metal materials cost about 50, and the surveyors fee was 75. I hired a 90 degree drill to drill the joist centre holes, for about 25.
HTH.
Phil
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wrote:

I meant Structural Consultant's fee, fo that is what he called himself, though without any of the fancy initials mentioned by others.
Phil
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Phil Addison wrote:

Thank you very much Phil, that is very helpful. While there are significant differences between the houses - for instance my joists run parallel to the proposed rods - it gives me a pretty good idea of what's involved.
I've got a structural engineer coming to take a look tomorrow (for a somewhat higher fee than you paid yours!). I'll post results.
Thanks again.
--
Grunff


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There are some pics of it at http://www.pando.pwp.blueyonder.co.uk/TieRods/index.htm
Phil
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Grunff wrote:

<snip original post>
The structural engineer has just been and gone. He appeared to be very knowledgeable, and had lots of qualifications.
In short, he believes the wall has moved both downwards and bowed outwards. Partly due to settlement of the cut and fill, and partly due to the rear porch having no discernable foundations.
Top marks to mark for coming to almost exactly the same conclusions without even seeing the place!!
He (the engineer) said that there's no need to take any action, but that there may be some future movement, accompanied by cracks to the interior plasterwork.
He suggested that putting in a tie or two, tieing the back wall to the floor joist(s) may alleviate the cracking. Which is oddly where my question started out...
So there. Nothing to worry about. Thanks to everyone who gave sensible, reasoned advice.
--
Grunff


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Dont forget to keep a copy of his report safe and, once you have done your DIY, get him to return and provide a certificate of satisfaction, (or similar). This way, when you come to sell, you will have documents to prevent a buyers surveyor second guessing the worst case scenario.
When the time comes, make sure your estate agent has copies of the documents, and make absolutely certaing that any buyers surveyor receives copies at the time of the survey.
--
Richard Faulkner

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I was talking to a builder friend the other day about my tie-rods, and he said that he would simply have rebuilt the wall. He reckoned it is a straightforward job. I can't say I'm convinced, but if feasible it would avoid any future awkward questions from prospective buyers.
-- Phil Addison The uk.d-i-y FAQ is at http://www.diyfaq.org.uk / Remove NOSPAM from address to reply
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