Framing a paving slab??!?!

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craigfda
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Framing a paving slab??!?!

Post by craigfda » Tue 14 Aug, 2018 6:27 pm

Evening!

I have been asked to frame 50 paving slabs (10.28 kgs worth per slab- 40cm x 40cm)

I have agreed with the customer to use this float moulding from Arqadia:

https://www.arqadia.co.uk/productdetail ... 471&id=197

I have a few ideas about drilling and screwing the slabs onto hardboard or plywood but would be grateful if anyone could give me any tips/pointers for framing such a heavy item.

Many thanks in advance,

Craig

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Re: Framing a paving slab??!?!

Post by misterdiy » Tue 14 Aug, 2018 8:05 pm

I guess the first question would be "why do you want to frame 50 paving slabs? :shock:

Once over that, I agree with you in using the tray frames, however, unless these slabs were rare then the value is minimal and hence I would glue the tray of the frame to the slab after having fixed the hanging system to the slab which is the difficult bit, but I would fix the slabs directly to the hanging system and make that the only fixings to the slab. The frame would be ornamental in this case and take no weight.

I would not finish off the slabs either unless there was a really good reason to do so.

As for the hangings system, I would be inclined to bolt the "hooks" (and they will take some sourcing) directly to the slab probably using epoxy to fix the bolts into the slab. Its a very heavy load to be hung, but i dont thing the wooden frame has any chance of surviving that weight

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Re: Framing a paving slab??!?!

Post by Not your average framer » Tue 14 Aug, 2018 8:49 pm

Paving slabs! Whatever next? I'm wondering how you are going to secure the fixings into the paving slabs, that is assuming you are still intending to drill the slabs. it's probably worth considering fixing some M6 studding into the holes with chemical metal and fitting nuts and locking washers at the rear of the frame. I also would be careful not to over tighten the nuts when fixing the slabs into the frame, just in case. Unreinforced paving slabs are unlikely to have any published stress rating, so it may be wise to play it safe.
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Re: Framing a paving slab??!?!

Post by GeoSpectrum » Wed 15 Aug, 2018 7:34 am

I'd be tempted to have floater frames made from steel or alloy L profile to house the slabs and bind them into place with {something}. You could also use 'clips' fashioned from alloy and bolted to the steel frame to hold the slabs in place. You might also check your insurance......
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Re: Framing a paving slab??!?!

Post by craigfda » Wed 15 Aug, 2018 9:51 am

misterdiy wrote:I guess the first question would be "why do you want to frame 50 paving slabs? :shock:
Ha! Yes, indeed- basically it's for a contemporary art exhibition. Each slab will be "decorated" by an artist.
misterdiy wrote:Once over that, I agree with you in using the tray frames, however, unless these slabs were rare then the value is minimal and hence I would glue the tray of the frame to the slab after having fixed the hanging system to the slab which is the difficult bit, but I would fix the slabs directly to the hanging system and make that the only fixings to the slab. The frame would be ornamental in this case and take no weight.

I would not finish off the slabs either unless there was a really good reason to do so.
Aye, I was thinking that the slab itself will have to take the weight of hanging, as even a bulky frame will break. What do you mean by finishing off the slabs?
misterdiy wrote:As for the hangings system, I would be inclined to bolt the "hooks" (and they will take some sourcing) directly to the slab probably using epoxy to fix the bolts into the slab. Its a very heavy load to be hung, but i dont thing the wooden frame has any chance of surviving that weight
I think the biggest problem will be that the bolts can't go through to the front of the slab, as that is where the artwork will be displayed. Do you know of any particular hanging methods for supporting bulky items?

Thanks for your reply, Misterdiy! Greatly appreciated

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Re: Framing a paving slab??!?!

Post by craigfda » Wed 15 Aug, 2018 9:53 am

GeoSpectrum wrote:I'd be tempted to have floater frames made from steel or alloy L profile to house the slabs and bind them into place with {something}. You could also use 'clips' fashioned from alloy and bolted to the steel frame to hold the slabs in place. You might also check your insurance......

Would be a great solution but unfortunately the customer has insisted upon a wooden frame. May try to persuade them though. Thanks!

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Re: Framing a paving slab??!?!

Post by craigfda » Wed 15 Aug, 2018 9:58 am

Not your average framer wrote:Paving slabs! Whatever next? I'm wondering how you are going to secure the fixings into the paving slabs, that is assuming you are still intending to drill the slabs. it's probably worth considering fixing some M6 studding into the holes with chemical metal and fitting nuts and locking washers at the rear of the frame. I also would be careful not to over tighten the nuts when fixing the slabs into the frame, just in case. Unreinforced paving slabs are unlikely to have any published stress rating, so it may be wise to play it safe.
Great tips, thanks! Was thinking that I would have to drill and then use bolts but the biggest difficulty will be not being able to fasten at the front, as I'll not be able to break the surface of the slab. Maybe 3/4 of the way in and then use some chemical metal, like you suggest. :yes: It's only 29mm deep, mind you, so maybe I won't be able to drill that far into it.

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Re: Framing a paving slab??!?!

Post by misterdiy » Wed 15 Aug, 2018 10:07 am

By finishing off, I meant a back and tape. I would just use a frame round the slab leaving the rear of the slab visible, so that the hanging system can be sorted.

Mark's idea (NYAF) of using chemical metal could be a good idea. Its the Hilti bolt type system, but as mark says you have to be extremely careful not to stress the hole as the slabs will snap quite easily in my experience ( not for framing I hasten to add, but i did try and drill and use a Hilti bolt in a slab (50mm thick) and it cracked when tightening up)

Drilling a clearance hole into the slab and using an epoxy resin to hold them may be the best answer.

I must admit I have never had to hang anything this heavy to be honest, which is why the Screwfix catologue may be your best bet for sorting a hanging system.

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Re: Framing a paving slab??!?!

Post by Not your average framer » Wed 15 Aug, 2018 12:23 pm

How much do you know about concrete? The binding agent in concrete is calcium and much of the calcium in normal concrete fails to bond with other calcium in the concrete as it sets. Where super strength concrete is required, any un-bonded calcium will bond with sodium silicate if the concrete is soaked in a solution of sodium silicate. In other situations, sodium silicate can be added to the concrete as it is being mixed and the increase in strength and structural integrity is nothing short of amazing.

Try searching for sodium silicate concrete on the internet, I have not done this myself, but there should be some info to back up what I have said.

If you can adequately stabilize the surface of these paving slabs, then the possibility of getting a good adhesive bond to the concrete becomes a realistic option, but I would still like a secondary fixing method just in case, for complete peace of mind.

Is it acceptable to use any form of support contacting the sides of these slabs? I am thinking about using friction and a conformable materials which under pressure conform to the inherent roughness of the surface of the concrete. This is not as silly as it be at first sound, but is a recognised engineering practice. What do you think?
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Re: Framing a paving slab??!?!

Post by prospero » Wed 15 Aug, 2018 1:44 pm

It's the old story. If the artist had drilled the slabs and embedded bolts in the slabs BEFORE they were worked on it would
have made life infinitely simpler. If a blank slab got cracked in the process - no big deal.

A bit of forethought goes a long way. As is, the artist has made his problem your problem. :|
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Re: Framing a paving slab??!?!

Post by Jules007 » Wed 15 Aug, 2018 2:14 pm

Have the slabs actually been decorated by the artists yet?

If not then tell the client that you need to drill and attach the fixing bolts beforehand to avoid damaging the decoration and if any slabs break then they can be replaced.

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Re: Framing a paving slab??!?!

Post by GeoSpectrum » Wed 15 Aug, 2018 7:18 pm

Lion sell an alloy inlay frame with a wooden veneer covering. Thinner than the one you have discussed with your customer but probably stronger.
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Re: Framing a paving slab??!?!

Post by JFeig » Thu 16 Aug, 2018 1:08 pm

There are industrial epoxy compounds specifically designed for the insertion of bolts into concrete. No torquing down on the bolts is necessary.
I agree with Prospero, The drilling should have been done by the "Artist". It should be his responsibility if the slabs crack. You have no idea of any internal flaws in their creation. Ideally, the slabs should be drilled with water-cooled carbide bits.

Or they could have been cast in a mold with inserts where the bolts should be.
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Re: Framing a paving slab??!?!

Post by Not your average framer » Thu 16 Aug, 2018 4:28 pm

JFeig wrote:There are industrial epoxy compounds specifically designed for the insertion of bolts into concrete.
Yes, my local builders merchant stocks the one I mentioned, which is called chemical metal. It not particularly cheap and you are going to need quite a bit of it with so many paving slabs.

I've already been enquiring about this because the stairs to my flat above my new shop have no banisters and I was asking how I could fix the banisters into a 1600's cob wall and this was their recommendation.
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Re: Framing a paving slab??!?!

Post by A3DFramer » Fri 17 Aug, 2018 7:53 am

I think you might have put the cart before the horse in choosing the moulding before the method of hanging.

At first I thought this an interior decor job for a manufacturer of slabs. So this idea might be a bit off, but I will describe my initial thoughts so they may be some help. I would weld or have made angle iron frames, so that the slabs can be dropped into the frames front forward. Have the sides of the frames pre-drilled so that the edges of the slabs can have a shallow counter sink hole drilled into them. The holes in the angle iron tapped to take countersunk grub screws so that they will bite into the slabs on all four sides. I would then start to think about the moulding to hide the angle iron frame. The angle iron frame would would have the method of hanging the slabs attached to it.

But as this is a gallery concept, I would want to run a test, like suspending the framed slab upside down across two trestles and giving the back of the angle iron some hefty clouts with a 1 1/2lb ball and pane hammer, the a 4 lb lump, even perhaps an 8 lb sledge hammer. The idea of 'chemical metal' might also be used. If this is the substance used to replace the old method of setting iron bars into stonework using molten lead, may be an epoxy resin of some form in a mastic type tube.
'I have some in shed at the moment waiting to see if there is yet another method of making glass cases, still to be discovered.' :rock: old timer :giggle:
This stuff could be used as a back up to the grub screws, or might even work with a dexion type frame, used in a similar way. Though I can imagine this path might get a bit messy. :Slap:

Your predicament reminds me of another gallery idea, where the cart got put before the horse. This one had plenty of money to spend by the sounds of it. The idea was to bond 5 pieces of glass with 45 degree bevels together into a case, but the glass had to be tempered first. As the glass goes over rollers in the tempering process, very slight waves are formed and this produced imperfections that did not sit well with the gallery. After two attempts the first contractor, took to the hills, the replacement was confident he could do the job, fortunately I was only a bystander and never found out if they managed to satisfy the gallery. The person I was helping was just making the pedestal the glass cover was supposed to rest on.

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Re: Framing a paving slab??!?!

Post by craigfda » Tue 12 Feb, 2019 5:51 pm

Taken me a long while to get back to all of you on this- sorry! Your suggestions were greatly valued. I managed to, very carefully and with a bit of help, drill into the slabs and put bolt insert nuts into the holes. This was after I had attached a square piece of 10mm ply onto the back (it filled in the "aperture" in the tray frame.)

I was asked along to the exhibition to advise with hanging and when I got there, joiners had started attaching wooden cleats, directly onto the frames, ignoring the bolt inserts!! They had even hung a couple on the wall. I got them down pretty sharpish and showed them the inserts. Disaster averted and a fantastically successful show followed.

4 Walls covered the job in their October 18 and Jan 19 issues, if anyone's interested!

https://larsonjuhl.co.uk/content/files/pdf/4walls30.pdf

https://larsonjuhl.co.uk/content/files/ ... alls31.pdf

Thanks again for all your help.

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