Cover steel externally

[johnny2007]

My friend had his massive window replaced with a smaller one and the steel above it was left exposed by the disappearing builder (see picture).
They want a canopy over that window (there was one there originally), so another builder proposed to fit wood in the steel and hung the joists off it as you would do internally.
I disagree with this because the steel would remain exposed unless unsightly foam is used to cover the gaps.
I've proposed to fit insulation board in the steel recess and fill gaps with foam, them fit a wooden plate longer than the steel basically covering it and start the canopy from there.
In future they want to extend the canopy further left, so having the wall plate at brick level will make everything better imo.
All of this without considering the thermal implications of leaving a steel virtually exposed, although covered and dry from above.
What do you think?
(In second picture is my proposal, red line is insulation board, blue line is wooden plate protruding either sides of the steel)

 

[^woody^]

If the steel was there previously and there was a canopy, what covered it?

 

[johnny2007]

If the steel was there previously and there was a canopy, what covered it?

There was a flat wooden canopy with lead top.
It was as thick as the steel and cladded from underneath.
Basically it was like a small roof with two posts to hold it at the front.
Now they want a longer canopy with the corrugated transparent roof.

 

[RonnyRaygun]

With regard to corrosion do you know what protection the beam currently has?
It looks like it’s painted but might be galvanised underneath.
Either way, I’d give it a couple of coats of protective coating, although if it’s going to be covered by a canopy it won’t be fully exposed to the elements and so exposure will be limited.

As it’s a cavity wall there shouldn’t be any issue with thermals due to the cavity separating the beam from the inner leaf. In fact, the standard methods of supporting external leaf brickwork over an opening (proprietary lintel or beam on inner leaf with welded bottom plate supporting the outer leaf) will introduce a small thermal bridge.

I think joists into the web of the beam I with noggins between them is the best option - if you put a ledger board in front of the beam how are you going to fix it to the beam? I guess if you aren’t planning to span the canopy joists onto the timber board then it’s not so much of an issue?

 

[^woody^]

I suspect hiding it will look worse than seeing it.

Otherwise an alternative would be to clad the whole area enclosed by the canopy as part of the design of the canopy.

The insulation situation will be no different to how it was before, so if there were no problems before, then insulating it now won't offer any advantage

 

[johnny2007]

I'm told that there are 2 separate steels, one on the outer leaf, one on the inner, so no problems with thermal bridging.
The steel has been there 90 years and it was painted red with some superficial rust.
The builder repainted it.
The reason I suggested to go with the wooden plate at brick level rather than inside the steel, is that they will eventually extend the canopy to the left, so another plate would look ok.
Knowing now that there's no chance of thermal bridging, maybe a few knoggings in the steel would suffice.
I can drill and tap the steel in 3 points to hold the wood with exterior bolts.