Structural calculations - any experts on here?
Discussion
I'm in the middle of renovating an apartment in France and have hit my first major problem. The frameless glass balustrade on the mezzanine floor is not fixed well enough and has 10mm of play at the top edge. We're thinking of building up more timber at either side of the base, but I'm not sure how high that would need to be to secure the glass. The glass in the stairs is rock solid, but that has much more beneath the surface and a shorter projection.
The measurements
The joists are 140x140mm
The glass is 15mm toughened (see below)
At the moment it sits 100mm underneath the floor level with 1m above (French regs)
Fixing a handrail would probably sort it, but so much effort and expense has gone into having frameless that I don't want to give in that easily. I'd rather lose the clean glass-to-floor design and build up some more timber than stick a handrail on.
Any suggestions for how to make this safe?
The measurements
The joists are 140x140mm
The glass is 15mm toughened (see below)
At the moment it sits 100mm underneath the floor level with 1m above (French regs)
Fixing a handrail would probably sort it, but so much effort and expense has gone into having frameless that I don't want to give in that easily. I'd rather lose the clean glass-to-floor design and build up some more timber than stick a handrail on.
Any suggestions for how to make this safe?
Could you not use the profile channel thats normally supplied for such glass installations and hide it in the timber / finished cladding? That is what I have done in the past.
Like this this and you then hammer in the plastic wedges in the gap between the channel and glass...
I am sitting next to a 3.7m long single piece fitted this way and I reckon it moves 1-2mm max.
Like this this and you then hammer in the plastic wedges in the gap between the channel and glass...
I am sitting next to a 3.7m long single piece fitted this way and I reckon it moves 1-2mm max.
From the picture it looks like the fixings in the timber need to be higher, closer to the bottom edge of the glass. I would use two rows of fixings, staggered along the length.
I would think that the movement is in the timber clamping member. You could use a structural resin to infill the gap, would make replacement etc a real bugger but should stop any movement.
Looking at it a little further you could remove the white timber and the outer clamping timber and replace them with deeper sections to go the extra 25mm to the full depth of the ceiling, this would give a bigger lever arm to resist the overturning moment and therefore reduce the deflection.
Are you screwing through the holes in the glass by the way?
I would think that the movement is in the timber clamping member. You could use a structural resin to infill the gap, would make replacement etc a real bugger but should stop any movement.
Looking at it a little further you could remove the white timber and the outer clamping timber and replace them with deeper sections to go the extra 25mm to the full depth of the ceiling, this would give a bigger lever arm to resist the overturning moment and therefore reduce the deflection.
Are you screwing through the holes in the glass by the way?
Edited by Desiato on Tuesday 8th October 19:38
Only way to guarantee minimal movement is to clamp the glass to something properly solid - concrete or serious steelwork - or use the correct ally channel (FH Brundle do a side mounted one as well as a base fix), and then securely fix that to something immoveable. Timber won't cut it. Even if you use the ally channel and side bolt it to the joist, I reckon the joist will still twist.
For me that joist needs to come out, to be replaced with a big chunk of steel. It's probably the cheapest option as it can be fabricated to maintain the exact same layout without getting any glass remade. An engineer may be able to think of an easier way though
May be worth considering a U channel trim clipped on the top edge of the glass - 12 or 15mm x 15mm so not as obvious as a handrail - to link the pieces together and reduce the movement a bit, hopefully tying into the staircase glass somehow.
We used 150 square galvanised steel C section with 4 90 degree turns around the building perimeter, all resin bolted to 7N blockwork, then the ally glazing channel bolted to the C section. Not going anywhere, and still moves a few mm if you push hard enough.
For me that joist needs to come out, to be replaced with a big chunk of steel. It's probably the cheapest option as it can be fabricated to maintain the exact same layout without getting any glass remade. An engineer may be able to think of an easier way though
May be worth considering a U channel trim clipped on the top edge of the glass - 12 or 15mm x 15mm so not as obvious as a handrail - to link the pieces together and reduce the movement a bit, hopefully tying into the staircase glass somehow.
We used 150 square galvanised steel C section with 4 90 degree turns around the building perimeter, all resin bolted to 7N blockwork, then the ally glazing channel bolted to the C section. Not going anywhere, and still moves a few mm if you push hard enough.
andy43 said:
Timber won't cut it. Even if you use the ally channel and side bolt it to the joist, I reckon the joist will still twist.
For me that joist needs to come out, to be replaced with a big chunk of steel. It's probably the cheapest option as it can be fabricated to maintain the exact same layout without getting any glass remade. An engineer may be able to think of an easier way though
The joists are 140x140 so I don't think you will get much if any twist in those, the issue in this instance I am sure is the clamping timber and it's fixings. Any twist in the joists could be taken out with a noggin back to the second joist if that was an issue.For me that joist needs to come out, to be replaced with a big chunk of steel. It's probably the cheapest option as it can be fabricated to maintain the exact same layout without getting any glass remade. An engineer may be able to think of an easier way though
Desiato said:
Looking at it a little further you could remove the white timber and the outer clamping timber and replace them with deeper sections to go the extra 25mm to the full depth of the ceiling, this would give a bigger lever arm to resist the overturning moment and therefore reduce the deflection.
Are you screwing through the holes in the glass by the way?
Makes good sense. Yes, the glass is screwed through the holes, though we'll have another go tomorrow with much thicker bolts to try and fill the holes but also get a really tight fix.Are you screwing through the holes in the glass by the way?
Gruffy said:
Desiato said:
Looking at it a little further you could remove the white timber and the outer clamping timber and replace them with deeper sections to go the extra 25mm to the full depth of the ceiling, this would give a bigger lever arm to resist the overturning moment and therefore reduce the deflection.
Are you screwing through the holes in the glass by the way?
Makes good sense. Yes, the glass is screwed through the holes, though we'll have another go tomorrow with much thicker bolts to try and fill the holes but also get a really tight fix.Are you screwing through the holes in the glass by the way?
Furtehr thought from me, will won't the glass be attached (possibly routed) into the wall on the right hand side (as you look from the balcony)?
Thinking that there are 3 glass panels to the right hand one will be as secure as a secure thing, so there's got to be some way to tarsnfer the rigisdity of this panel to the other 2.
So some sort of insert, H shape steel strip? I hear what you say about they panels are cut to the exact width and know your love of symmetry but would it be too offensive to your eye to dig the right hand side of the right hand panel further into the wall? This would also give it more stability wouldn it not.
(say hiya to marmoit and Mrs B)
Thinking that there are 3 glass panels to the right hand one will be as secure as a secure thing, so there's got to be some way to tarsnfer the rigisdity of this panel to the other 2.
So some sort of insert, H shape steel strip? I hear what you say about they panels are cut to the exact width and know your love of symmetry but would it be too offensive to your eye to dig the right hand side of the right hand panel further into the wall? This would also give it more stability wouldn it not.
(say hiya to marmoit and Mrs B)
The glass is cut to very precise measurements, so setting a panel into the wall would leave gaps that are bigger than 10mm (regs). That only space I'd be comfortable having larger than that is agains the wall anyway. We've got some ruddy great bolts now and I reckon they'll do the job as is. We'll find out this afternoon.
Or make a feature to fix problem.
Make a few small'C'channels the thickness of the glass with a gap for rubber insulator, make in Brass Stainless or fancy Iron, weld a similar rod onto channel affix some plates to ceiling joists and affix rod to ceiling plates, two or three would create a feature and also lock the tops of the glass to the ceiling. Not clean lines but an option.
Make a few small'C'channels the thickness of the glass with a gap for rubber insulator, make in Brass Stainless or fancy Iron, weld a similar rod onto channel affix some plates to ceiling joists and affix rod to ceiling plates, two or three would create a feature and also lock the tops of the glass to the ceiling. Not clean lines but an option.
How about a polished aluminium handrail along the top of the glass? If need be it could be fixed into the wall at either end for extra strength?
I worked on a project a couple of years ago that had curved glass balustrading - the only way to get enough strength into that was to introduce a handrail along the top, which looked lovely in the end. The photo below isn't great but gives you an idea of the overall appearance.
ETA - can you take a photo or do a sketch section through of how the glass sits in it's channel? In the case above, the glass sat in a u channel which was then filled with a pouring structural compound to close off the gaps between the glass and the channel - this may be am option?
I worked on a project a couple of years ago that had curved glass balustrading - the only way to get enough strength into that was to introduce a handrail along the top, which looked lovely in the end. The photo below isn't great but gives you an idea of the overall appearance.
ETA - can you take a photo or do a sketch section through of how the glass sits in it's channel? In the case above, the glass sat in a u channel which was then filled with a pouring structural compound to close off the gaps between the glass and the channel - this may be am option?
Edited by tleefox on Wednesday 9th October 12:24
I understand. We did consider it, but the reason for trying to go frameless is to avoid having a visual barrier at that height. The ceiling is only 2m so frameless glass would/will make quite a difference to how open the space feels.
If the current plan doesn't work then we'll be building up the base a bit. If that doesn't work then we'll be adding a handrail or a length of steel at the base.
If the current plan doesn't work then we'll be building up the base a bit. If that doesn't work then we'll be adding a handrail or a length of steel at the base.
Gruffy said:
The glass is cut to very precise measurements, so setting a panel into the wall would leave gaps that are bigger than 10mm (regs). That only space I'd be comfortable having larger than that is agains the wall anyway. We've got some ruddy great bolts now and I reckon they'll do the job as is. We'll find out this afternoon.
The 10mm maximum gap that you have quoted seems small. Is that a French reg that you are conforming to?In the UK, Part K Building Regs, states no gap greater than 100mm.
Not wishing to insult you at all, but you haven't got mm and cm mixed up have you?
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