Wall fasteners for 75mm stud wall?

[MJNewton]

Having stripped back the dot-and-dab plasterboard from a bedroom wall I now need to route four 75mm OD semi-rigid ducts from floor to ceiling. To conceal these, and reinstate the wall finish, I will be building a stud frame out of 75mm x 50mm timber.

 

Unfortunately, whilst the base plate can be screwed down to the floor joists the joist hangers of the ceiling joists mean I won’t be able to affix the top plate to anything so the lateral loading will have to be accommodated by fastening the studs to the wall. My question is: what fasteners would your recommend, noting the ~75mm stud depth and limited scope for noggins for stiffness? If it’s relevant the wall finish will be 12.5mm PB + skim and whilst I don't anticipate putting heavy shelves up future owners might well do.

[ToughButterCup]

This what I use, I have often been accused of over-engineering things. 120mm Thunderbolts

[ProDave]

10 minutes ago, MJNewton said:

Unfortunately, whilst the base plate can be screwed down to the floor joists the joist hangers of the ceiling joists mean I won’t be able to affix the top plate to anything so the lateral loading will have to be accommodated by fastening the studs to the wall. 

I would just drill a clearance hole in the bottom of the joist hanger and screw through that into the joist.

 

No doubt someone will now tell me why that will cause everything to become structurally unsound?

[PeterW]

12 minutes ago, MJNewton said:

the floor joists the joist hangers of the ceiling joists mean I won’t be able to affix the top plate to anything

 

Can you elaborate ..?? Can you fit blocks either side of the hangers and use screws up through the wall plate into those ..??

[Russell griffiths]

As peter said, can you go in the loft and fit noggins between for trusses then come down and screw into the noggins. 

 

If this is downstairs then then there is a multitude of 125mm frame anchors that will do the job. 

You can get the concrete anchore screws in 125mm also, so no plug needed. 

[MJNewton]

Thanks everyone for the initial thoughts/suggestions. I'll take, and post up, some photos this evening to help illustrate the situation - apologies I should've done this at the outset.

 

In the meantime, I should add that there is actually another floor above this bedroom (so no easy access like there would be in a loft), the wall is block (light/medium-weight?) and the joists are engineered I-joists. Also, the plasterboard ceiling is affixed to resilient bars so sits ~16mm down from the joists - not sure if this is relevant other than the extra distance (gap) that would generally not normally exist.

 

Will post back with the pics so you can revise any suggestions if required in light of the full story!

Edited September 2, 2019 by MJNewton

[Mr Punter]

Can you just fix some brackets onto the wall at the top with screws and rawlplugs, then screw into the side of the stud to hold it firm?

 

https://www.screwfix.com/p/sabrefix-heavy-duty-angle-brackets-galvanised-60-x-50mm-10-pack/61576

[MJNewton]

I think all of these suggestions are probably valid; and I should add that by asking the question I have perhaps given the impression that I think it is a difficult problem to solve - I don't think it is but am never the less keen to hear of new (to me) ideas/products or whether a 'just use what Ive got' approach might suffice.

 

On to the pics, here's the wall in question:

 

 

(Ignore the duct routing - they're just hanging there! Oh, and don't highlight the less-than-ideal noncontinuous dot-and-dab method that'll almost certainly exist throughout the house!)

 

And here are the joist hangers; photo taken from another room where I've taken the ceiling (plasterboard and resilient bars) down but the wall boards are still up:

 

 

The 'cradle' of the hangers protrude ~80mm into the room so just about the size of my stud depth.

 

If the hangers already hand a hole drilled in the bottom I think I'd be laughing - I'd locate them and drive a decent depth screw up through but for some reason I am nervous about drilling my own hole in them just in case that causes any weakness!

[ProDave]

Yep I would just personally drill say an 8mm hole in the bottom of the joist hanger and insert a wood screw through that into the wood to fix the top plate.

[MJNewton]

I'm warming to that idea - certainly sounds the easiest and most straightforward method and having thought about it further can't see how it could cause issue. Assuming of course drilling through the metal is achievable which given all my HSS drill bits are the ones made from cheese that you get in a multi-pack when you first buy a drill will unlikely be the case! Any bit recommendations? (Ideally from Toolstation/Screwfix for ease of reference)

[Simplysimon]

not a fan of the black and yellow, however, these are superb. make the metal seem like cheese as opposed to the bits

https://www.screwfix.com/p/dewalt-straight-shank-hss-co-metal-drill-bit-set-29-pcs/1979v

[MJNewton]

I'm sure they're great but at £69.99 I hasten to add that I only want one bit! (Hopefully)

 

Edit: I see they sell them individually so will take a further look!

Edited September 2, 2019 by MJNewton

[MJNewton]

I did this job today and, as Simplysimon said, the Dewalt drill bit was a dream to use - it was like the proverbial hot knife through butter.

 

Edited September 13, 2019 by MJNewton