How to fix to RSJ?

[JoinerMike]

Hi guys
I have a job next week fitting some sliding doors into an opening which divides 2 rooms. This is a relatively new build and have been informed by the customer that the only thing above is a RSJ.
Now the system that the sliding doors use is the weight of the doors hang from the top rail so it is vital that the rail is fixed well. What fixings, screw etc can I use to screw the door frame to the underside of the plastered RSJ? so I can screw the rail to the frame securely?

Thanks in advance for any advice and ideas
Mike

 

[foxhole]

Do have a link to the sliding doors? most modern systems run on the floor avoiding the need for heavy framing. Will the doors be full room height, again unusual as there is often room for an upper framework.

 

[JoinerMike]

It is a rail a shop provides to it's customer for turning standard 30" x 78" internal doors into sliding doors. The one I will be doing this time will be 3 doors. The first door on the left pivots on the floor and is guided at the top. The 2nd door is hinged to the first, however is fixed by a bracket at the top of the top which the door hangs off. So the weight of that door is taken by the top rair and obviously slides so the rail has to be well fixed long that point. Besides the system the frame at the top is about 2.3m. Without any weight hanging from this it will still dip in the middle over time. Im guessing the plasterboard at the underside is probably pink gripped on. I'm guessing it's probably not distanced enough from the RSJ to get a plasterboard fixing. Can you drill a small pilot hole into a RSJ? I'm guessing it will just burn the drill bit. Thanks for any suggestions

 

[foxhole]

You can drill the rsj, but you will have room above the doors for a substantial timber to span the gap and hanging door rails are fairly substantial, fixed at the wall there should be no deflection over a small distance like three 30'' doors.Ceiling fixing would then only serve to keep the alignment and take no weight.

 

[JoinerMike]

I also have to fit some French doors in the same property. So with that I will need the 20mm thick door casing not to dip. If I have room above I will fix eg a 4"x2" first by drilling into the RSJ. This will give me a nice gap to put some architraves on. So say I fix the 4"x2" with some 4" no 8 screws do I just drill the steel with a bit just slightly smaller than the screw thickness? Then on both doors I can fix my door frame to that.
Thanks again for your help

 

[foxhole]

You could use a 3.5mm hss for the no 8 screws or use self tappers.