Torsion box shelf in alcove with stud (kind of) wall advice

[Noel]

I've got to build a torsion box shelf in the morning in an alcove, one side solid wall, other side has been sheeted with plaster board (just found out) over the original chimney breast and as far as I can tell, not a stud in sight ( : )). There's about a 2/3 inch gap between the sheet and the chimney breast, which could well be filled with scrunched up newspaper rather than a proper timber frame.....there's plenty of flex. Might be a stud halfway up the wall but that's no help.
I don't have a lot of faith in plaster board fixings, especially as there is likely to be a reasonably heavy TV on the shelf eventually.
So, I was thinking about cutting/slotting into the plaster board to fix directly to the brick work. It might be a bit fiddly when applying the top and bottom boards (6mm ply) to the torsion box frame but seems the only safe and secure way. And some hassle making good too but the family has a few kids so best to be safe.

What do you all think? Can't think of any other way.

Thanks in advance.

 

[NazNomad]

The plasterboard fixings will only really be under shear-pressure which should be plenty strong enough. It's not like they are holding an unsupported load on one side only.

A couple of beads of Gripfill on the end of the shelf won't hurt either.

 

[user22161]

You could drill and plug the chimney breast and use copper tube or similar spacers to sleeve long screws so you're tightening up against the spacers, not just the plasterboard.

 

[Jacob]

Er - alcove has three sides but you've only mentioned two? You couldn't fit a heavily loaded shelf to plasterboard alone. From what you say it sounds like you need to remove plaster board back to the nearest studs/noggins, fit your shelf (to a new noggin?) and then make good with plaster board. Otherwise it sounds like key hole surgery.

 

[Graham Orm]

Er - alcove has three sides but you've only mentioned two? You couldn't fit a heavily loaded shelf to plasterboard alone. From what you say it sounds like you need to remove plaster board back to the nearest studs/noggins, fit your shelf (to a new noggin?) and then make good with plaster board. Otherwise it sounds like key hole surgery.

Ditto to that.

I'd slot the PB, & cut a batten that will reach from the brickwork out to the face of the PB. Drill half way through the batten with a large spade bit in 4 places. Put a large screw in the face of it to use as a handle so you don't drop it down behind the PB. Hold it in place with your 'handle' then masonry drill through the middle of the large holes made by the spade bit. Plug and fix to the brickwork, remove the 'handle' and fix your shelf to it. You'll need a long masonry bit, the large holes will let the chuck of your drill further in. Some SDS bits are long enough for this but I doubt you'll find a conventional masonry bit long enough. Before now I've ground the SDS shank off a bit and used it in an ordinary hammer drill, when I'd forgotten my SDS.

 

[No skills]

Answered your own question, if your worried about it remove a section of plasterboard and fix timber to the brick where required. Stitch the plasterboard back in and make good. Build shelf as normal remembering to screw through the plasterboard in the correct places to hit timber.

As an aside I've become a big fan of concrete screws rather than the typical large rawlplug for fixing timber to masonry, easier to do and less hit n miss as to how good a fixing you get. Fwiw.