Need To Anchor Into Concrete But Only Have 40mm Before Hitting Steel Beam?

4 May 2016
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United Kingdom
I'm building a lean-to but the only place I can anchor it on the house is a concrete lintel that spans the entire width of the house.

Problem is I could only drill 40mm into the concrete before I hit a steel beam.

What would be the best way to anchor?

I'm trying to attach joist hangers so the roof doesn't get lifted in the wind as opposed to running the screws through the wood and into concrete.


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Pictures would help. I'm struggling to conceive a concrete lintel that can span an entire house (at least 5m?), yet has a thickness of just 40mm
Pictures would help. I'm struggling to conceive a concrete lintel that can span an entire house (at least 5m?), yet has a thickness of just 40mm
I think it's a steel beam which has been filled with concrete to make it look nicer.
I'd drill the concrete and the steel and wind a fixing (like a concrete screw; it'll cut the steel if you back n forth it enough) through the whole lot, or if you can get to the back side of the steel, a bolt through it all. Won't need many to fix a ledger onto which you can secure a lean-to, as there isn't a lot of downward force from such a lightweight roof, snow-loaded or otherwise

That's assuming you're not up for cutting the concrete at the start and the end and bashing it out to replace it for wood (hilti gunning it on will be particularly quick but drilling and screwing will also work fine. You can then joist hanger it easily
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Nah no ledger has been installed. How would I drill through the steel beam? I tried with a HSS bit from ALDI and was taking ages.

What about expandable concrete wall plugs? I can't find them in 40mm sleeve lengths but if I can would they be strong enough here?
Use resin and threaded rod to install a horizontal ledger or plate running in same direction as beam, and the. Nail your brackets to that makes sense to me - rather than individually trying to fix brackets to the concrete
What diameter hole are you trying to drill? If it's 6mm or above then you are best to drill a 3 mm pilot hole through the steel and then work up by 1mm or 2mm diameters at a time.
Don't even think about drilling with the correct size if above 6mm dia as you will simply burn the tip out.
I tried with 8mm then stepped down to 6mm and it began shredding some metal off but was still taking forever.

What drill bit is recommended? I mean brand and all.

And no ledger! I fluffed that idea since it was originally the plan. Ended up using ledger wood as noggins. If I use resin fixings would they even hold in 40mm?

Could do brown plug but would it be strong enough to prevent wind lift off?
An Aldi bit won’t do it.
I would get some Cobalt bits from Toolstation.
you’d need a decent drill as well.

Or fit a timber above the lintel.
I would start with 3mm then 5 followed by 6 or 6.5 then finally 8mm
Remember, if you are using 8mm bolts you should drill to 8.5 or even 9mm clearance for the thread to pass through.
But assuming you can't get to the other side of the steel to fit washers and a nut then you would need to drill a 7.5mm hole and tap an 8mm thread with a tap wrench & tap.
Note though that a 3mm drill bit might not stick far enough out of the end of the drill to reach a steel that is 40mm deep in concrete..
..but starting with the smallest bit that will reach would help

When conny talks about taps they're referring to something like this:

Practice using them first; I find it easiest to start a tap by putting it in a drill on very slow speed so I can concentrate on keeping it well aligned with the hole before moving to the T handle to cut the thread proper
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Or fit a timber above the lintel.
That was the plan until I realised there's nothing behind that white cladding! Wall is literally cladding > insulation > plasterboard. Like an internal wall of a new build. Nothing to attach to.

I will try step up the drill bits when I'm next there. But why not just use the 3" wall plugs I bought in an 8mm hole? I have a tap and die set but seems overkill versus just plugging it.
Is it a steel beam, or have you just hit a reinforcing bar in what would be an insitu reinforced concrete beam?
I've come across a few houses built after WW1 which incorporate a full-width r.c. beam.
If it was a steel 'I' beam and you hit the web, the depth of concrete would be far more than 40mm (unless you were unlucky enough to hit the edge of the flange).

Edit: or is it a post-WW2 non-traditional build?
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