6/18/2005
what would be the recommended thickness of glass, for a glass shelf that would span 5’ft. and is 5″in depth. and be supported by a support cleat on each side(no center support)? Approximate weight load would be about 50-60lbs – dispersed kitchen items – (olive oil, small cannisters, tea cups…) Is there a more suitable type of glass other than tempered glass?
Thank You! Chipper
Listeners write in about fireplaces and ask questions about sharpening hand tools, easier wiring upgrades, and fixing cedar siding.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial NowGet instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
Replies
Thats a lot of weight on a 5' x 5" strip of glass. You better check with a glass fabricator.
In the meantime I would suggest dadoing a continuous channel in the wall or backer to help share the load. You might get away with a thinner less expensive piece of glass
it will be open space on the front and back side of shelf. it is an open window partition wall between a kitchen & dining room. Therefor, the only spot to tie in the shelf would be on the 2 end sides. 5"deep.
I'm not sure about the properties of glass, but if you get the glass a little longer than the opening you could creat a very subtle arch. This could keep the glass from bowing down under load.
You could also run a thin steel wire back and forth a couple of times on the underside, attached to brackets at the end. Putting tension in the wire will help the load capacity of the glass (bridge building technique)
Another idea - Use a long acrylic piece 7" wide, heat and fold the edges down, creating a 5"x1" C channelRebuilding my home in Cypress, CA
Also a CRX fanatic!
have you actually done and tested this idea or are you just spouting off here? Glass under tension that breaks can send shards flying as projectiles that could kill or seiously injure someone.IMO, this glass will need to be at least a half inch thinck and probably more.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I agree, thats a narrow piece of glass. I think its gonna have a noticeable sag in the middle even without any knick-naks.
I'm betting he may have to ratchet up to 3/4". Thats just an uneducated guess.
I'm just giving a glass manufactorers standard recommendations.
I've done hundreds of glass shelves. Each application is different. Tempered glass can also cause injuries when it explodes. Not to mention that when it breaks everything on it will be lost.
Additional support is always a great idea. If an annealed glass shelf is fully supported, you have a better chance of eliminating fall out and containing your items. If the glass is laminated your chances are even better. If you are worried about saftey, then laminated glass is a must! From what I know so far I would recommend 3/4" thick glass at least.
Edited 6/19/2005 12:23 pm ET by glassguy1
Sorry - it was not you I was questioning about the idea of introducing a camber/crown to this glass shelf, but a previous post. We all happened to post about the same time, so mine fell in line rtight after yours. As a newbie, you may not have noticed it was adressed to the other guy.Thanks for good inforamtion.Another idea, I had while out was to affix another piece to this one so there would be a "T" cross section to give it support. Personally, I liked the idea of the "C" channel edging to strengthen it
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Those were some ideas to take to his glass fabricator. I thought it has he himself who mentioned that when I typed my ideas. I also stated that "I do not know the properties of glass". If he finds a type of glass that does well in compression, then perhaps it could work even better with a little engineering brought in from other fields.
Just some ideas to be accepted or rejected, ruminated on and tried or dismissed.
And if you don't know EXACTLY the thickness he should use, aren't you just spouting off here? Glass under tension that breaks can send shards flying as projectiles that could kill or seriously injure someone ya know.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Touche`!
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I appreciate everybodys insight & advice - THANK YOU!
I love the idea of using steel wire on the underside of the glass shelf. I am unfamiliar with this technique, but very curious & would love to add extra support underneath that would not really impinge on the working space - great idea! What type of brackets would be used? kerfed metal plates, lipped plates, thread ferrules......?
I will be going up to the local glass manufacturer tommorow(Tues), to talk with them and order glass. Thnaks Again for the help!!!!!! I appreciate it!
chipper
talked to glass manufacturer & came up with the conclusion that the best solution would be stranded steel wire with adjustable glass support clips and mounting plates for top & bottom. The hardware alone would cost approx. $250 & the glass would cost approx. $65. Customer did not prefer spending that much in material expenses, & resorted to have 3/4" x 5" X 5' oak wood shelf installed, with wood supports.
Phew - the customer will be MUCH happier without the glass! I realize that usually our default approach is solve the technical problem rather than ask why. Why would someone want to use a clear shelf for things like olive oil, that are always dripping, leaving rings, etc. Kinda like those glass range hoods - always dirty! OK, I'm better now :-)
Unless you want that glowing green edge of the glass affect, you could slide the glass into steel channel front and back and mortise the channels into the supports at each end. Or you could place the glass on one or two angle irons running across and under them (sort of like ...Paul..'s idea of wire). Even wire glass (glass that has like chicken wire imbedded in it) might have more strength. At any rate, that or safety glass would be less dangerous if it did break.
According to some old data that I have from a glass manufacturer, the permissible load for annealed (standard float) glass is as follows:
1 2 3 4 5 distance between supports
1/4" glass 49.4 10.5 3.3 .080 0
3/8" glass 196.7 45.5 17.5 7.7 3.2
1/2" glass 345.4 81.4 32.6 15.4 7.5
The numbers above are pounds per square foot, based on two sided support. A general rule of thumb is to multiply the above numbers by three if the glass is tempered. Most manufacturers do not recommend tempered glass for shelving due to the slight possibility of spontaneous breakage. Some people still use it, but you should explain the consequences to your customer. We always use caution with glass shelves, the thicker the better. Even with minimal loads, at least 3 in every 1000 will break when loaded close to the maximum permissible load.
If the green hue is a problem, there are low iron glass options on the market. This glass is not 100 percent clear (a slight blue hue), but some people love it. Not worth the added cost though (i.m.h.o.). Hope this helps.
50 to 60 pounds of kitchen knick-knacks? seems a bit high, but it's your kitchen :-)
its actually for a client, and 50-40lb was a high-end assumption on the weight. but, ya never know what somebody may set on there so i figured to estimate a higher weight bearing to be safe.
Sorry, I sent my reply to the wrong person on my first post...
Two more options for your situation would be to use 3/4" float glass which has a 23.3 pounds per square foot load at a 5'-0" span. Or you can go with laminated tempered glass. The problem with laminated glass is that there could be some overlap during the lamination process, resulting in a slightly offset edge. The laminated glass edge is not very attractive. The interlayer adds an unslighly line through the glass, which turns most people off to it's use.
I cut and polished an entire jewelry store full of 3/4" inch glass shelves once - similar size. The original shelves we cut were from 1/2 and sagged without any weight on them, so out they went. 3/4 is a pain to work with, it's pretty hard to snap too.