One for the engineers

[RogerS]

This was the original problem

A large crack developing due to the foundations shifting. And getting worse.

My proposed solution was to have fabricated out of 16mm mild steel a tie bar which came in three parts and joined like this

only either my measurements were wrong or they made it to the wrong length because this has happened

The individual tie bars are too long for me to take back to modify them. I don't have any welding kit. Nor do I have a die and stock large enough to thread the bar myself and so I thought drill a hole through the bar.

So I started small....3mm and put in a wire nail..which promptly sheared off once I tightened the bar up and so my questions are as follows:

1) what size hole can i safely drill in the bar (16mm dia) before I weaken it

2) what should I use instead of the nail? A bigger one? HSS stock .but not sure where to get a piece in small quantities and how would I stop it falling out of the hole as I seem to remember that HSS is brittle and so can't be bent like a nail

3) Is this a sensible route to take or is it weaker than a nut?

4) Given that steel expands/contracts, when should I tighten up the bar?

 

[OLD]

If you do fix the tie bar and it continues to move it will crack else were .
time to get out the spade and find out whats happening ,underpinning can be just digging holes and casting concrete blocks under existing footing so that the wall is acting on a greater area.
You may be able to bend the bar at right angles to make it shorter not the best looking solution or use a nut and bolt through the rod

 

[Lord Nibbo]

Roger are you sure it is a foundation problem? It looks more like a shrinkage problem to me. How old is the wall?
Most modern walls have a shrinkage gap every 15ft even buildings are designed around the problem of shrinkage. To give you some idea a 100ft long wall can in theory shrink 3" yes 3"...

 

[RogerS]

Reason why I think it's a foundation problem is because the gap is much, much wider at the top of the wall than the bottom. So my theory is that the wall is dropping on one or both sides of the crack. The tie bar at the top is supposed to stabilise it...and what was done in the house by our builders when we bought it.

This wall is around 8-9 years old, I'd say IIRC

 

[jasonB]

Its probably due to the ground drying out with the dry weather, iif we get a decent amount of rain the gap will likely close up again.

A 6mm hole will be about as large as you can go, this will leave just over half the cross sectional area of the tie rod. Use a bolt as the pin preferably a grade 8.8 or higher. Put some washers on the rod so pressure is applied to both sides of the bolt or cut the bolt head off flush one side.

Jason

 

[RogerS]

Thanks, guys for the suggestions. Reckon I will go for 6mm as Jason suggests and see how it goes.

Any recommendations as to when to tighten the nut up? At maximum thermal expansion? I have no idea how much thermal expansion there might be in a 16mm bar about 10m long.

 

[OLD]

10 metres long ! i can not see this working . If you are just waiting for the subsidence to stop then bolting front to rear through the crack would be a better measure best to cure at source.

 

[RogerS]

Well, Old....I hope you're wrong :wink: as the missus has got an awful lot of plants near the base of the wall and wouldn't be best pleased me suggesting she dug them up while I went excavating .

Mind you, the wall falling down doesn't bear thinking about

 

[paulm]

Heat and bend the excess rod to 90 degrees, then tighten up with the nut at the opposite length. Cut off any excess rod from the bent end leaving a couple of inches or so.

Obviously the measurements will need to be reasonably accurate bearing in mind the amount of thread available at the nut end of the rod.

Ultimately though it's only a sticking plaster !

Good luck.

Cheers, Paul.

 

[engineer one]

frankly roger i am having a great deal of trouble figuring why you
would use a 16mm bar over 30 feet 10metres. presumably you
are tying back to something, but what??

if you are not going to dig, which given that we are going into winter,
and many of your wife's plants may not be there much longer, or
could do with moving, should be the best solution. then why not
tie along the wall rather than across it??

as suggested i would not think about more than approx 1/3rd of dia for hole, and then what about a bar from an old fashioned tube spanner.
but looking at your pictures, it seems that the thread part has stretched,
so you may have problems in tying it back.

my personal solution is a bodge, but, cut the 10m bar in half in the
middle, beg borrow or steal a tap and die set, and then use one of
the old fashioned turnbuckles to keep it strained in the middle.

you cut some out of the middle, and then tap each end, and
then put that through the turn buckle, put a nut on each piece, and then
tighten to increase the strain again.

but as the irishman said to me in dublin "if i were you i wouldn't be
starting from here!"

good luck
paul :wink:

 

[RogerS]

Hi Paul

The bar is down the length of the wall and ties back to the two pillars at either end..that was the plan, at any rate :wink:

I'll probably try the easier option of drilling through a larger hole..and see how we go.

Watch this space...literally and metaphorically

 

[engineer one]

roger, having been out, i was thinking in the odd moments, and i
wonder whether the 16mm bar is going to be strong enough in
the long run? i think over the length, it may well stretch very
quickly, particularly if the wall starts to move again.

will think more, and maybe the light bulb will work, :?

but certainly to ensure proper tension, you need to use a turnbuckle.

paul :wink:

 

[les chicken]

Roger

Had a similar problem with my dividing garden wall 30ft long 7ft high my side 4ft high neigbours side. We had a discussion got a friend who is a decent brickie to inspect.

Only one answer knock it down sort out the foundations and start again. Not the answer you are looking for but, the thought of it falling over onto the granchildren or the dog sealed the decision.

Les