Frameless Glass Balustrading on a steel structure

[D Walter]

We are looking to install frameless glass balustrading on a balcony, bottom fixed to painted galvanised 200 x 150mm 8mm RHS steel box section, and on a terrace bottom fixed to concrete.  My current issue relates to the balcony which will require 1100mm high balustrading tested to 0.74kn/m2.  We are looking at the various anodised alloy channel systems (PanelGrip, OnLevel etc..).  The recommendation is that 17.5mm toughened laminated glass is acceptable provided it is fixed at 200mm centres but that the better option is 21.5mm toughened laminated glass which can be fixed at 600mm centres.  I assume that the different fixing centres for thickness of glass is related to the potential for flexion damage. 

 

We are intending to use M10 Type 316 SS bolts for fixing, bolted into tapped holes in the RHS8 so as to avoid through bolting the box section with nuts underneath.  My concerns are a) the potential for galvanic corrosion between the galvanised steel, the SS bolts and the aluminium channel, particularly given we are on the Isle of Wight and have some salt in SW gales; and b) whether bolting into tapped holes in 8mm steel will be sufficient. 

 

Any thoughts/advice would be most appreciated.  We will be using Galvafroid to seal where we are tapping through the galvanising wherever possible.

 

Incidentally, it looks like the best prices we can find are on F. H. Brundles site where they offer a number of different systems and competitive glass prices.

 

Thanks

David

[PeterW]

I’m not sure tapped holes are acceptable but an engineer would be able to advise 

[Russell griffiths]

I was going to say the same as peter, the thickness of your box section may not be thick enough to resist pull out, I have fixed handrails before ( not glass ) and the box was cut and internally plated to add thickness to the bolt areas. 25mm thick I seam to remember but it is many years ago. 

[Ralph]

Hi David, 

 

I would be very interested to see how this turns out for you. We keep being steered away from frameless balustrades. We’re told that over time the panes shift slightly and it’s difficult to keep them aligned. This seems to be more of an aesthetic issue than a structural one.

[D Walter]

Thanks for the input everyone.  I will get some SE advice on this.  As for adjustment over time, some of the systems are easy to adjust after initial fixing and some impossible...

[D Walter]

Hi,

 

Quick update - my Structural Engineer says that securing the bottom fixed alu channel with M10 Type 316 SS bolts into tapped threaded RHS 8mm mild steel box section is fine.

 

On the issue of frameless glass balustrading moving out of alignment over time, this should hopefully not be a problem with most of the dry-fixed systems where the rubber gasket can be removed and spacers adjusted.  Some systems requires a tool for removal of the spacers (usually also required for installation) and others have spacers which are adjustable by means of, e.g. allen bolts.

 

If I experience any problems I will do a subsequent post.

 

David

[jack]

On the subject of frameless glass, my main point would be to make 100% sure that you have every detail worked out, especially drainage (including how you handle any leakage into the channel supporting the glass).

 

I overlooked these details on our (admittedly timberframe) build until too late, and it's added a lot of stress, delay and cost trying to sort something out.

[Pocster]

Like this ??

 

 

[D Walter]

Hi Pocster,

 

Looking at your photo, have you used anodised alu channel for the frameless balustrade and was it bolted into galvanised steel?  If so, what sort of bolts did you use and were you able to take any precautions against galvanic corrosion?

[Pocster]

24 minutes ago, D Walter said:

Hi Pocster,

 

Looking at your photo, have you used anodised alu channel for the frameless balustrade and was it bolted into galvanised steel?  If so, what sort of bolts did you use and were you able to take any precautions against galvanic corrosion?

Erm !

The steel beams are indeed powder coated I believe . The installer supplied bolts etc. - it was a custom job so I did nothing ?. I can later get a photo underneath so you can see the bolts - from memory there’s no sign of corrosion..... yet !

[D Walter]

Thanks Pocster.  The risk of galvanic corrosion between alu and galvanised is relatively low in any event. 

[Pocster]

Not sure how helpful this photo is . After a year no obvious sign of corrosion