Securing insulated plasterboard to steel lintel

Do you mean with some self-tapping screws? I did consider that, and not sure why I moved to the plugs. I would presumably still require pilot holes?

Is this all indoors, totally protected from rain/moisture?

In my limited experience, I'd glue it (with insulating foam maybe), making sure it's properly supported while the glue goes off. Then fix/glue the plasterboard over. I'm probably missing something, but it's so lightweight . . .

Yes; I'm just insulating the internal reveals.

I must admit I am tempted. It never ceases to surprise me how effective adhesive can be, particularly when applied over large areas. I remember dismantling a conservatory and removing a ridge beam from a side wall - I was sure I'd got all the screws out but it just wasn't budging... It turns out a full length of silicone was still keeping it place.

I would use dry wall adhesive or coving adhesive which is very similar, both will need some support initially. If you are plastering walls around the opening then you can apply plaster direct to the lintel just press the initial bonding coat into the gaps to maximise adhesion.

Richard

Good point. :)

Yes, I am keen to ensure there is at least some insulation around the reveals (although the door frame width means there won't be all that much).

I'll be making my own plasterboard+insulation sandwich and so it'll be foil backed. I too had read that dot-and-dab adhesive doesn't stick well to it, but it seems that most 'tube' adhesives do.

Problem is that that situation, you'll blunt the drill with the first hole you drill when you go through the lintel into the aerated concrete blocks above it. So you will need to sharpen the drill after each hole is drilled.

Better to glue the insulated plasterboard to the lintel with a decent glue.

You need a hilti gun and some ammo. They will nail into RSJs with the correct ammo.

What's wrong with using self drilling screws? They come in a variety of lengths and are the standard for roofing contractors attaching insulated sheeting to steel purlins

Can't see that being viable, getting the right amount of the nail sticking out of the lintel. Those nails rely on the head stopping it going into the lintel and the plasterboard/ insulation composite isnt going to stop the head.

Glue would be much more practical.

Your basic plan is fine, but get yourself a set of cobalt drills, Toolstation does a cheap set, or Bosch do them individually or as a set. A bit more expensive than TS but *very* good.

The advantage over "normal" high speed steel "metal" bits is that they won't blunt when you go through the metal even if you hit normal brick or blocks, rather than lightweight.

That type of lintel ought to be easy enough to drill. RSJs are sometimes more difficult partly because of the section thickness, and you can also hit non-metallic inclusions.

There's a bit more skill in drilling metal than wood or masonry, you need to have the right combination of pressure and drill speed and it all depends on the size of hole. But a 6 mm hole with a normal domestic mains or cordless drill should be no problem. Slow speed and quite a lot of pressure, you should be able to "feel" when it is cutting.

Overkill for insulated plasterboard.

I'd just go with the low expansion foam, and suitable spreaders to hold it in place for an hour or two ... I've done that with about 3/4 sheets with no problems.

Drilling metal is always a problem for the timid,use as much pressure as possible without breaking the bit, at a slow speed and your drill will last for many holes without sharpening.

Use one of the foam adhesives which will not only stick to the surface of the lintel but expand into the slots in the lintel.

example

I've recent had some work done on my house and this type of adhesive was used to bond some wood to a sandstone type surface prior to plasterboard being screwed to the wood and then skimmed. Excess foam was easily removed with a knife albiet there wasn't much excess because it was alow expansion foam.

FFS just glue it in place

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