I have a belvedere or cupola in my new house that currently functions as a light well. I would like to install a floor about 11′ above the floor below which will give a person seated up there a view out. The inside dimensions are 7′-2″ square. I will need about a 20″ x 40″ hole for a ship ladder on one side. I want to make the floor transparent so as not to lose the light this structure provides to the spaces below. I am considering steel grating, glass or plexiglass. The floor system should also be light in mass, again to maximize transparency. I can use structural steel tubing or hardwood, with members spaced 16″ to 24″. Building inspection will not be a factor.
Anyone out there have any experience with something like this?
Replies
>Building inspection will not be a factor.
Thats priceless!!! Lawsuit may one day be a factor!
J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
Let me clarify. I have been living in the house for over a year and this is an improvement that I am doing myself. I have been in construction for 25 years and am a registered architect. I have a very good working relationship with the local building inspector, and this project will be of interest to him as it is not something he has come across before.
greg,
How about some glass block? CR makes a system.
http://www.circleredmont.com/91R%20Paver.htm
KK
KKearney,
That looks like a good system. I will look into it. Cost may be a factor. I tend to try unconventional methods and applications. My home is sort of a laboratory. Thanks
You could also add a little steel grid so that the glass does not have much of a span and use laminated safety glass.
you can get glass any thickness you need..
prison glass is designed to stop 357 roundsMike Smith Rhode Island : Design / Build / Repair / Restore
If you want to do something unusual, you might try constructing a grid of fairly thin steel, like about 2" high by 3/8" thick, on maybe 30" centers. Infill with panels made up of a sandwich of plexi, same 2" thickness, with a grid of plexi in between the layers. Not sure if this is a box beam, or what you call it, but it is the same idea that is behind corrugated cardboard. Because the plexi panels are clear in both surface and structural elements, the whole structure should seem pretty airy. I am guessing at the dimensions; you are the architect, so you can calculate better than I. It would require cutting and gluing a lot of plexi strips, though.
Why not explore glass? The stacks in the old library at Olivet College had floor panels of glass. I think that they were about an inch thick. The glass was also about eighty years old when I was there and was pretty well frosted from wear, so you couldn't look up for inspiration.
So, since you're an architect, you must have figured that walked on glass will scratch, and will no longer be transparent, unless you have different definition of transparent...oh, wait a sec, you're an architect, slap me silly.... It's okay, I can fix it!
Hey Bucky
Youre becoming more rambuncious then me now....how dare you! lol
Be well
Namaste'
AndyIt's not who's right, it's who's left ~ http://CLIFFORDRENOVATIONS.COM
Greg
If you can, have a look at the architecture of bridge design by David Bennett. Published by Thomas Telford Publishing in 1997 and available in the US through the American Society of Civil Engineers. ISBN 0 7277 2529 7
The book contains two examples of foot bridges built of glass. My favourite is the one in the Science Museum in London, a picture of which is attached (if I can master attaching files). This bridge is 6ft wide, not much different to your span. The bridge deck is made up of glass planks 6 ft wide, 3 in deep and 3/4 in wide supported only at the ends on what looks like a 3/4in stainless steel tube. The detail in the book suggests the glass planks are really 3 inch strips of 3/4 in glass stood on edge. The planks are laminated into 6ft long panels. In your case you should be able to cross the light well in a single span.
The other glass bridge is in Paris. It uses flat glass strips suported on a relatively heavy frame. The slipperiness of the glass is overcome by using denser or anti-slip glass for the alternate strips.
keep us posted.
Very pretty. Thanks for posting the picture. I bet it cost a small fortune to build.
Depends on what you describe as a fortune. The tender price for the bridge was 200,000 British pounds for a 14 metre long structure - ie about 4,500 British pounds per foot. My guess is that the cost of the glass was only a small fraction of the total cost. The supporting structure, which uses about 200 1mm diameter stainless steel wires each individually cut to length, positioned and tensioned would have been expensive. The interesting thing is the architect positioned the glass on its edge rather than going for sheets of thick glass.
Not to say it is not worth it. The bridge is a working work of art and beautiful besides.
200k british:
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Over $300,000. is a fair chunk of change. I grew up in a medium sized suburban house, it is still nice if a bit small by McMansion standards, that even now would go for less than $70,000 including the land. A family of five lived comfortably and wanted for little for over 40 years. I'm not sure the million dollar houses are really much better than that old house.
You're right, the bridge is mostly a work of art and that has greatly influenced the price. Still USD$316,000 for a 14 metre span works out at about USD$1200 per sq ft, which is arround about average for a highway bridge! However, your comments on reasonable house prices are interesting. I live in Sydney and here the average house price is about USD$175,000 including land. The McMansion style starts at about USD$350,000 and sits on a 7,000 sq ft block. From there the sky's the limit.
In relation to how this thread started, installing a glass floor in a light well, the Science Museum footbridge example suggests that if you install glass on its edge, relatively large spans are possible. If you cross the light well in a single span, you dispense with the need for a frame, except at the edges, and use maybe 4 times as much glass as for frame and pane construction.
I'm waiting for comments from the original poster. He described himself as an architect so it would be interesting to know how the Science Museum example grabs his imagination.
Dear Ian
I just installed a glass roof that we use a a babeque area - its cool during the day as it is milk white sand blasted and cool at night as we up light with colours from beneath.
Specification
32mm thick laminated - cost £650 British pounds per m2
or converted to US - US$933 per M2 ( about 10ft sq = 1m)
This does not include the struture needed to hold the glass in place ( about 100 - 150 per m2)
The biggest factor is the size of the glass that you ( well you and 8 friends) can lug into place. It heavy in the old fashined sence. A good glazier and an understanding engineer will sort the whole thing out. The building inspector should not worry if you can prove the calculation
good luck
Phil
I'd recommend speaking to a representative of an architectural glass manufacturer. They have all the calculations, strenths, safety factors, support requirements, etc.
Essentially what they will do is calculate the maximum tensile stress on the bottom surface and specify enough thickness so that the stress does not exceed the strength of the glass. With glass they use a healthy safety factor. I think the allowable tensile stress will be around 1000 psi.
Support is important. There can be no point loading. So, I'll bet they specify a gasket of some kind underneath the glass.
have a look at http://www.circleredmont.com/