Resin anchor fixings

[robngill]

I am in the process of renovating an old cottage and need to fix a steel angle horizontally along the internal face of an old stone wall. This is part of the construction of a new floor which will also help to support the old wall, which has moved slightly (probably many years ago). The walls are 500mm thick!

Anyway, the steel angle is 90x90x8 and is drilled with three 16mm holes. I have been advised to use resin anchors to secure the angle to the wall, though it has also been suggested that 'thunderbolts' would do a good job. These fixings will be supporting the wall, so I want them to be strong under tension.

I see that most resin anchors appear to be M12 or less. I had assumed to use an M16 bolt (hence the pre-drilled M16 holes in my angle), but now have some doubts whether this is appropriate.

Can anyone advise whether an M16 resin anchor would be the right approach, and if these are the best fixing for old masonary walls.

I assume thunderbolts are the same as coach bolts?, and I guess that the use of these would depend on me finding a solid bit of stone to screw into? Now that my steel is predrilled, this might not be the case. My inclination is to stick with the resin anchors.

I would be grateful for any tips or advice. Rob

[JoeJoe]

I am no expert on the matter, but from previous experience it sounds like the kind of information (not advice!) that you should receive from a structural engineer, based on his/her calculations.

[somebody]

In message , robngill writes

Get a suitable resin. Drill an M16 hole, clean out the hole, squirt in resin and twist in an M16 stud. AIUI this is a fairly standard approach for steel fixing into masonry, concrete etc.

Once that's done, I would be inclined to then inject/squirt/trowel a proper bedding grout into any gaps between the steel angle and the (probably) uneven wall.

As for whether the whole approach will be strong enough... I have no idea :-) Best talk to an engineer.

Hth Someone

[Andy Dingley]

They come in all sizes. You don't see over 12mm much because you can rarely attach a fixing with a load that needs a bolt that large and find stone that can take that load in such a small area. Toolstation sell up to 16 mm though.

Bolts certainly aren't appropriate in resin, nor are many standard thread profiles. Best to buy real studs intended for use with chemical anchors.

Not always the best, but if there's the slightest problem then they're far better than a metal expanding anchor. Those are the ones that really cause problems.

If you're stuck then you just can't put big loads into crumbly stone through a single fixing. You have to use a spreader plate and more fixings. Probably with a stunt geologist too.

[Steve Walker]

Yep, as long as you use enough of them, and drilled deep enough, this'll hold an ocean liner onto the side of your house (in my DIY not-a-builder-or-engineer-etc experience).

Noting Andy's comment below about suitability of stud or bolt for resin, I must admit I've often knocked a slight bend into the rod end for peace of mind, but I don't think it's strictly necessary. In my experience (emphasis as above) the hardened fixings are completely rigid & secure.

[meow2222]

Resin is the way, but I hope you dont mean youre going to support a floor on just 3 metal studs :)

NT

[robngill]

Thanks to everyone for the advice. This has given me confidence that the resin anchor is the right approach, though I will discuss it further with a structural engineer, as advised. The anchor grout sounds like a good idea too.

The local Builders Merchant has offered a metre length of M16 threaded bar to use as the anchor. This is nice and cheap, but would proper studs provide a significantly better performance?

For the record, these are not holding up the floor! That is to be supported by two 152UC32 beams. The angles are to be bolted between the beams and lie against the walls to reinforce the tie between the two opposing walls. The tie will also be assisted by the beams themselves. Hope that makes sense!

Rob

[somebody]

In message , robngill writes

Unless the bar is graded I'd go for proper studs. They may or may not be

*better* performance but they are a *known* performance. Nuts/Bolts/Studs are rated for strength, see ...

I don't know if you've got a local fixings specialist, if not try a steel fabricator/erector. Either is less likely to give you that 'blank' look when asked "M16 x 100mm SA8.8 stud" for example :-)

I think so but it does sound like a job for an engineer to specify.

Hth

[Andy Dingley]

You get a few advantages with studs:

- Clean steel. If it isn't already, then degrease the studding with acetone.

- The right thread profile. Some finer threads have problems with air entrainment, especially if dirty, and so can have massive loss of contact with the resin. People (climbers and cavers) get killed because of this.

- There's a stop on most resin studs so that you're tightening down onto a fixed flange, not putting the tension immediately onto the resin. Of course you're still applying a torque here, unless it's a big stud with facility for locking this too. Usually it makes no difference, but it can do if you're using a large high-torque nut onto a wek hole.

[robngill]

That all seems to make perfect sense. Studs it is. Many thanks Rob

[Rick Hughes]

Smiled as just bought 50 M16 expansion bolts to bolt down a load of plates

[Rick Hughes]

. In my experience

Do you torque up the fitting after the resin has set ? ... and can they take significant torque ?

I have to do up a load of M16 expanding sleeve bolts and the spec calls for

100NM (74 Lb ft)

[Andy Hall]

It's like doing up the clamps for transformer laminations. Tighten until it breaks and then back it off half a turn.