Conservatory roof tie

[DIYspanner]

A wood beam roof that's gradually sunk and pushed on the window frames and spilt them.

I'm planning to install a cable type tie and have considered using 6mm steel rope to tie between a couple of eye bolts that I'll screw into opposite inline beams.

Has anyone made a roof tie with steel rope?

 

[Burnerman]

How are you going to tension the wire, D Spanner?
Have you considered threaded bar which could make it easier? I have before had two strips of steel, with a flange welded to each end, and pulled together with a 12mm nut and bolt......a bit agricultural but that's me!
John

 

[DIYspanner]

For tension, I've considered a couple of options.

A turnbuckle wire tensioner OR perhaps using a jack and long post, push up on the centre beam (which I've already done to ease the window frames back together) then get the cable taught and clamped with u bolts, then lower the jack to put the tension on the cable.

 

[Burnerman]

The turnbuckle tensioner is very effective - used it on wire fencing a few times.
Personally I wouldn’t use the jack, but tension your wire gradually to heave it back into place.
I’ve used my method to brace chimney stacks a few times, and just leave the metalwork in place.
John

 

[KenGMac]

Agree with Burnerman above, slowly slowly using a steel cabling, [say] 6.mm ?

Suggest you consider two of the following.type of tensioners?

https://www.amazon.co.uk/Turnbuckle-Tensioner-Strainer-Stainless-Tension/dp/B073TRQQQT

As for fixing to the rafters? possibly a plate bolted to each side of the rafter, with one bolt protruding to provide an anchor for the wire? the wirt bring a loop and held by two large washers and a bolt??

The fixing to the rafters needs consideration as the tension on the timber is really quite high and concentrated

Some time ago, I saw a Conservatory roof failure where on a PVC roof the fixings on the rafters [again PVC] simply poor design on a fairly wide Conservatory

Ken.

 

[DIYspanner]

A few ways to consider, thanks.

If using a turn buckle, I'd use a double eye type rather than one with a hook which could open under strain.

The type of beam fixing would be an M10 wood eye screw bolt. The bolt would be at angle to the cable strain so wouldn't pull out.

 

[Burnerman]

All points to consider, certainly but if a turn buckle hook was able to be pulled straight by the force of the cable, a 10mm eye bolt wouldn't stand much chance and would pull out of the beam, I think.....much better to bolt right through.
https://www.screwfix.com/p/diall-m8-rope-clip-zinc-plated-10-pack/382ht
These are good if you go down the cable route.
John

 

[DIYspanner]

I'll see how the cable works. I can use turnbuckles to tension and u bolts to lock. I had a look at this product and its similar to what I intend.

 

[KenGMac]

would pull out of the beam, I think.....much better to bolt right through.

Totally in agreement with the above, this area of the connection to the rafters is crucial.

IMO it needs a 15 or 20.mm threaded bar with a loop on one end, then two substantial plates on each side of the rafter, something like a 10.mm thick plate with a central hole, a reasonably close fit around the threaded bar.

Nuts and washers on each side.

If you consider it, the roof will set up a very slight vibration, the action of wind on the roof, any unsupported fixing under a lot of stress will fail by crushing the rafter??

Ken.

 

[Burnerman]

This structure should have been tied when it was originally erected.....to pull it back in now will need gentle tensioning over a period of time.
John

 

[mrrusty]

Agree with most of the above. Wire strop with properly made eyes with thimbles - you may have to get this made up - or threaded bar (12mm will be more than enough) with proper clevis end fittings. A turnbuckle will work. The key will be the fixing in to the rafter which must be very robust. A single bolt will be no good - the point load where it contacts the wood will just compress the wood - you need to spread the load around a bit. If it was me I would use a stirrup bracket bolted around the rafter fixed through the sides so the fixings are all in shear. The loop of the stirrup around the inner face providing the fixing for the tension bar/wire.

The problem you have is that I think this will only work if you tension across the end of the rafter much closer to where it meets the wall plate, otherwise I think the rafters will just bend inwards without actually drawing the extremities inwards - I don't think the rafters are big enough for the forces you create with a tie where you have drawn it to transfer to the rafter ends enough. If you think of the rafter as a lever with the apex as the fulcrum, if you tension from a mid fixing, most of the transferred force at the rafter end is downwards, not inwards.

As the wire will be too low if strung across at wallplate height, I would consider doing this, getting the roof where you want it and then fixing a permanent brace a little higher before you remove the lower tension brace.

 

[catlad]

I've done this once using 6mm steel cable, I went through the rafter with a 6mm drill a couple of times and then put a steel cable tie to stop it coming back through.

 

[DIYspanner]

A number of criteria to consider on this job. Thanks All!