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.
"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
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
18 mm tongue and groove chipboard flooring is nailed to the joists to form a
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
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.
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.
<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.
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.
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.
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