Fixing into pre-stressed reinforced concrete?

[Chud]

Morning all - bit of a random question here but I've got a greenhouse that is sat on a base of scavenged offcuts of pre-stressed concrete beams. Lengths are ~650mm- 900mmIts on an allotment so the obvious poured concrete base/foundation is a no-go.
I've got them all set and levelled, the greenhouse frame is now on top and the glass going in. I have put in a couple of fixings to stop it literally blowing away (live near the coast!) but on using brown rawlplugs (7mm hole) it has caused the side of the beam to blow out a bit (although the anchor still seems to be holding. I had to drill off centre to avoid the reinforcing bar in the beam.

What's peoples views on an alternative fixing - I'm thinking either:
1) Concrete screws - am i right in thinking they don't put as much expansive force on the material as the threads cut into the concrete?
2) Chemical fixing - obviously this would work but is probably overkill and ££

 

[stevie888]

Resin is the way to go. All you need is some 5mm studding cut to length (I'd go stainless) and some nuts and bolts. Make sure the resin you get will fit a standard mastic gun. I would also use a nylon washer to separate steel from ally.

 

[noseall]

Morning all - bit of a random question here but I've got a greenhouse that is sat on a base of scavenged offcuts of pre-stressed concrete beams. Lengths are ~650mm- 900mmIts on an allotment so the obvious poured concrete base/foundation is a no-go.
I've got them all set and levelled, the greenhouse frame is now on top and the glass going in. I have put in a couple of fixings to stop it literally blowing away (live near the coast!) but on using brown rawlplugs (7mm hole) it has caused the side of the beam to blow out a bit (although the anchor still seems to be holding. I had to drill off centre to avoid the reinforcing bar in the beam.

What's peoples views on an alternative fixing - I'm thinking either:
1) Concrete screws - am i right in thinking they don't put as much expansive force on the material as the threads cut into the concrete?
2) Chemical fixing - obviously this would work but is probably overkill and ££

View attachment 375715

Fix in the beam centre with say 50mm concrete screws. Job done. The screw heads may benefit from a washer.

 

[Ivor Windybottom]

Can't you hook under them with some sort of brackets, to avoid drilling?

Or even heavy duty cable ties

 

[Deluks]

As above, j-bolts, road pins hammered in, or what about these sheet roofing bolts?

Putting more holes in them will weaken their longevity.

https://www.amazon.co.uk/Compton-Ga...hvtargid=pla-2281435176938&psc=1&gad_source=1

 

[noseall]

As above, j-bolts, road pins hammered in, or what about these sheet roofing bolts?

Putting more holes in them will weaken their longevity.

It's a support for a greenhouse, lol. Putting a few holes in them won't amount to jack.

 

[phatboy]

A few concrete screws with Form A washers will be fine. Quick and easy.

 

[Deluks]

It's a support for a greenhouse, lol. Putting a few holes in them won't amount to jack.

But it is true that they will last longer without having holes drilled into them.

We don't know the desired lifespan of this structure, the OP could be on his last legs, wanting his greenhouse to see him out for a couple more years until he becomes compost for his own potatoes.

Conversely, he might be barely out of short trousers, in the flush of youth, looking forward to a lifetime of productive horticulture and brown fingers, in his greenhouse that he hopes will last him for 80 years and beyond.

 

[Ivor Windybottom]

I'd be more worried about the things just falling apart when drilled into, they can be pretty brittle.

Those j-bolts linked above look good.

 

[jj4091]

Just a tip for fitting the glass if you live in an exposed area, bed the panes on silicon sealer rather than rely on the clips.

 

[noseall]

But it is true that they will last longer without having holes drilled into them.

Nonsense. Have you ever worked with floor beams? They will outlive the greenhouse by about a thousand years, holes or no holes.

 

[noseall]

I'd be more worried about the things just falling apart when drilled into, they can be pretty brittle.

Lol.

 

[robinbanks]

Probably simpler to just use chunky cable ties to go round the whole beam, and frame. You may have to drill the frame to avoid the tie displacing the glass.

Be aware that using fixings that are not aluminium, and winding them in such that they contact the alu will promote galvanic corrosion. Use some electrically insulating spacer (eg a plastic washer) between the alu frame and the non alu fixing if you go this route

 

[cdbe]

How do you even walk on them? Must be like a cattle grid - or are they upside down. From the allotments I've seen a bit of blue rope won't be out of place.

 

[Chud]

Just a tip for fitting the glass if you live in an exposed area, bed the panes on silicon sealer rather than rely on the clips.

I lucked out - the greenhouse I got has screwed on bar capping in addition to the clips.