Shelf Support Issue

[Dan Mages]

I need a little wooworking advice for these built-ins. The shelving on both sides are 4'6" wide with pine shelves (in the basement being painted) That is very wide for a shelf without some sag. The previous owners used some additional material (a long lost shelf maybe? to stick between the shelves to help prop them up without sag. I need a cleaner option. would adding a 1.5" piece of trim to the front help brace it? Any other thoughts?

Sorry for the mess in the picture... It is amazing how much junk I was storing in the lower shelves.

[Adam Herman]

a 1.5 x 3/4 glued to the edge will stiffen it significantly when placed with the 1.5 vertically, is the shelf material 3/4? Could you put a shelf pin in the center on the back wall as well? a hardwood like oak or maple will be stiffer than pine.

[Edwin Santos]

There is a web tool called The Sagulator which you can google and find. It will give you guidance on what you will gain by adding supporting trim to the front (and if necessary the back) in different thicknesses. Here is the link:

http://www.woodbin.com/calcs/sagulator/

Hope this helps

[andy bessette]

...would adding a 1.5" piece of trim to the front help brace it?...

It won't prevent very visible sag, if the shelves are heavily loaded. Doubling the shelf thickness would be much more effective.

I would install barely noticeable center supports, such as thin metal standards, which could be painted to match the back wall. Alternatively a thin center divider could be installed.

[Dan Mages]

Thanks! I will check out the sagulator and look for metal standards that will match the ones I have now. Otherwise, I will adjust the front.

[Martin Wasner]

Add a vertical partition. I wouldn't put a 54" wide shelf in anything I sold with out the customer knowing up front that there is potential for issues. Not just sag either, you can put a zillion pounds of books on there and it has a pretty good likely hood of ripping out just about anything but shelf standards. I never know what people are going to put on shelves. Books, civil war cannon balls, feathers, spare cinder blocks, priceless antiquities, etcetera, that they are going want me to replace when something fails. Or worse, crushing a kid and I get sued into oblivion. I realize this is your house, and you can't really sue yourself, and you're in control of what you put on those shelves, just sharing my viewpoint.

I try not to go over 40". When I get up to that or a little over I double up the shelf edging, meaning I put an edge on the front and back. My standard shelf edge is 3/4" thick, and 1-1/4" tall.

[Brian Henderson]

Not seeing exactly what you're working with or how you are attaching to the wall makes it a bit difficult, but you can always just reinforce the shelf with metal. Get an appropriate flat bar or two, route a groove into the bottom of the shelf, epoxy in the bar, cover with a thin veneer of wood and you'll have a very strong shelf that looks no different than the original.

[Andy Giddings]

+1 on Edwin's Sagulator recommendation

[Lee Schierer]

The sagulator is a very good tool. For a floating shelf 54" long 7.5 inches wide made from 3/4" pine with a 50 pound distributed load it will sag 1/4" at the center. Adding a 3/4" thick by 1.5" tall along the front will reduce the sag for the shelf to ~1/8". You may get additional sag over time.

[Dan Mages]

Add a vertical partition. I wouldn't put a 54" wide shelf in anything I sold with out the customer knowing up front that there is potential for issues. Not just sag either, you can put a zillion pounds of books on there and it has a pretty good likely hood of ripping out just about anything but shelf standards. I never know what people are going to put on shelves. Books, civil war cannon balls, feathers, spare cinder blocks, priceless antiquities, etcetera, that they are going want me to replace when something fails. Or worse, crushing a kid and I get sued into oblivion. I realize this is your house, and you can't really sue yourself, and you're in control of what you put on those shelves, just sharing my viewpoint.

I try not to go over 40". When I get up to that or a little over I double up the shelf edging, meaning I put an edge on the front and back. My standard shelf edge is 3/4" thick, and 1-1/4" tall.
This is original to the house roughly 60 years ago. It is definitely a Yankee build. I found some leftover trimwork inside the lower cabinets to support the counter. I am not sure if I can sell my wife on adding a center divider. I might be able to redo the shelf supports on the sides with Closetmaid adjustable shelf standards and brackets. Inelegant, but totally workable.


Not seeing exactly what you're working with or how you are attaching to the wall makes it a bit difficult, but you can always just reinforce the shelf with metal. Get an appropriate flat bar or two, route a groove into the bottom of the shelf, epoxy in the bar, cover with a thin veneer of wood and you'll have a very strong shelf that looks no different than the original.
I have a close-up picture below of the inside of the built-in. The room is lined in this 3/4" thick double bead pine paneling (is double bead the correct term?). It is mounted over wallboard with a rough coat of plaster. The paneling is awesome, but a massive amount of prep for paint. I am caulking each seam, filling all of the holes and deep scratches, light sanding, a scrub with a brillo pad, prime and paint.... about 3 days of work per wall. Reinforce with metal? A little angle iron along the back?


The sagulator is a very good tool. For a floating shelf 54" long 7.5 inches wide made from 3/4" pine with a 50 pound distributed load it will sag 1/4" at the center. Adding a 3/4" thick by 1.5" tall along the front will reduce the sag for the shelf to ~1/8". You may get additional sag over time.

Thanks for running the numbers!

[Sam Murdoch]

If I had to build a shelf this wide I would include a riser on the front AND back. Not a bad idea to incorporate a bit of crown in the risers too.
An additional help would be another support stanchion with the clips in the center back.

[Brian Scheffler]

I'd be good with twice as many 27" shelves. 54" is like building an 8' cedar picket fence with 1x2's for posts. If its painted its a super easy fix. put in another 2x on each side. They're painted so even better!

[Ole Anderson]

Not seeing exactly what you're working with or how you are attaching to the wall makes it a bit difficult, but you can always just reinforce the shelf with metal. Get an appropriate flat bar or two, route a groove into the bottom of the shelf, epoxy in the bar, cover with a thin veneer of wood and you'll have a very strong shelf that looks no different than the original.

Brian, have you actually tried this? My considered opinion, short of your experience otherwise, is that one would see very little difference in a thin shelf. A long, thin, flat bar is very flexy, and even solidly glued to the wood, would add little strength. Burying it so a veneer can be used to hide it would put it even closer to the center of the "beam", you want any reinforcing steel to be as far away from the center as possible. Think "I" beam. Sorry, my old structural engineering classes are surfacing.

[Adam Herman]

you use the same idea and run a rabbit along the back edge for a peice of 1/2 angle. this would shurly provide enough stiffness. I like to cut a groove and dado into projects that need a little extra support to install steel angle.

[Dan Mages]

I did a little experiment this morning with a shelf standard and brackets from the Borg. I can install two of these on the back wall to prevent sags and use the clips on the side for additional support on the ends and along the front. I will also add a 4/4 x 2" poplar band to the front to the shelves. Will biscuits, glue and pocket screws be overkill??

Thoughts?

Dan

[Jamie Buxton]

Make the shelves thicker. Stiffness goes up as the square of the thickness. So if you go from a 3/4"-thick shelf to a 1 1/2" thick shelf, it is eight times stiffer. That is, the sag under load is one eighth of the sag for the 3/4" shelf.

Just looking at the pic, a thicker shelf would not look out of place.

[Sam Layton]

If you want to stiffen the shelves I like the following. If your shelf is 3/4" in thickness. Buy some 1/8 x 1/2 or 3/8 flat steel stock. Take your shelf and saw two kerfs 1/2" deep about 2" from each side. Epoxy the steel flat stock in the kerfs, and that should stiffen your shelves.

Sam

[andy bessette]

As Ole rightly pointed out, adding metal near the center of the shelf's thickness will accomplish very little. It is the material's extreme fibers that do most of the work. This is why doubling the shelf's thickness is so effective. And it is why adding an edge stiffener does very little; its extreme fibers are limited to just a narrow band.

[Malcolm McLeod]

Brian, have you actually tried this? My considered opinion, short of your experience otherwise, is that one would see very little difference in a thin shelf. A long, thin, flat bar is very flexy, and even solidly glued to the wood, would add little strength. Burying it so a veneer can be used to hide it would put it even closer to the center of the "beam", you want any reinforcing steel to be as far away from the center as possible. Think "I" beam. Sorry, my old structural engineering classes are surfacing.


As Ole rightly pointed out, adding metal near the center of the shelf's thickness will accomplish very little. It is the material's extreme fibers that do most of the work. This is why doubling the shelf's thickness is so effective. And it is why adding an edge stiffener does very little; its extreme fibers are limited to just a narrow band.

It takes very little material to create a strong beam (and that's what a shelf is). It just has to be in the right places.

...Andy, sorry but gotta go with Ole on this. The narrowness of the band has little to do with it. It has much more to do with the distance from the vertical 'center' of the shelf. Again, think of an 'I' beam; the (vertical) web can be very thin and still support a large load; this web moves some of the 'fibers' away from the center of the bending stress. The (horizontal) flanges are just there to keep the tall web from buckling side-ways. Its the same principle as a torsion box or a honey-comb sheet of composite. But all of this makes for a very unconventional look (some would say UGLY), and inefficient use of the space. So we throw a plank in and expect it to hold up the world.:eek:

Doubling the thickness from 3/4 to 1-1/2 will add a great deal to the anti-sag, but you could get virtually the same result with much less material (& $$) - - just add a 3/4"W X ~1-1/2"H 'web' (Dan's "band") to front and back of each shelf. ...I'd make the height of the band about 1/8" less than UGLY!:cool:

If you're in an experimental mood, compare 4 shelves of equal depth & span:
1. 3/4" thick
2. 1-1/2" thick (3/4" doubled)
3. 3/4" thick with 1-1/2" band (front and back)
4, 1-1/2" band (front and back) skinned with 1/8" ply or hardboard.
Load a shotput in the center and measure the sag.

I've never tried it, but I'll bet #4 wins (and has less material than any other).

[Edwin Santos]

If you want to stiffen the shelves I like the following. If your shelf is 3/4" in thickness. Buy some 1/8 x 1/2 or 3/8 flat steel stock. Take your shelf and saw two kerfs 1/2" deep about 2" from each side. Epoxy the steel flat stock in the kerfs, and that should stiffen your shelves.

Sam

That's a nifty idea! If you were very cautious,a third steel spline down the center would be easy enough.

Here's another idea that probably becomes a little too time consuming, but how about a web frame that you would skin on both sides, basically a 1" or so thick torsion box? The more cells, the stiffer it would be. I remember an article years ago by Ian Kirby that talked about the incredible strength of torsion box "floating" shelves. Again, there are simpler and faster solutions for your particular situation, but torsion boxes are an interesting way to solve various problems.

352597

[andy bessette]

MM--you misunderstand the premise of an I-beam. It is not the vertical web that is doing the work; it is the flanges, the extreme fibers. What you propose is building an angle (one vertical web) or a channel (two vertical webs), not an I-beam. The reason the double-thick shelf simply works is that the "flanges" of the "I-beam" are full width.

[Malcolm McLeod]

MM--you misunderstand the premise of an I-beam. It is not the vertical web that is doing the work; it is the flanges, the extreme fibers. What you propose is building an angle (one vertical web) or a channel (two vertical webs), not an I-beam. The reason the double-thick shelf simply works is that the "flanges" of the "I-beam" are full width.

I misunderstand a lot, just ask my Mechanics of Materials or Statics prof. But try this:
Build your own I-beam from some scrap plywood. Just for giggles, let's say it is 6" tall with 6" wide flanges. Load it and measure the deflection.

Now rip 2" strips off each side of both flanges. So now we have 6" tall by 2" wide beam (only 1/3 of the flange material:eek:). Now load it and measure the deflection.

By your estimation, would your beam have 1/3 the strength? ...3x the deflection? ...Something else?:confused:

Edit: Now rip the flanges completely off. If you used 1/2" ply, your beam is now 6" tall by 1/2" wide. I assume you assume the resulting beam would support virtually no load at all?

[Brian Henderson]

I have a close-up picture below of the inside of the built-in. The room is lined in this 3/4" thick double bead pine paneling (is double bead the correct term?). It is mounted over wallboard with a rough coat of plaster. The paneling is awesome, but a massive amount of prep for paint. I am caulking each seam, filling all of the holes and deep scratches, light sanding, a scrub with a brillo pad, prime and paint.... about 3 days of work per wall. Reinforce with metal? A little angle iron along the back?

I couldn't find a good picture online in the few minutes I had to look, but something like this: http://www.woodweb.com/knowledge_base_images/zp/preventing_long_span_bookshelves_1.jpg

[Dan Mages]

Oy. I have opened a can of worms here! I have minimal time, budget, and materials to make this happen. Adding dividers, building fancy torsion box shelves or multi ply shelves with rebar or other metal components is beyond what I can produce right now.

I did not want to mention this earlier and taint the discussion, but I am trying to make the room look good and ready if we sell the house.

[Adam Herman]

a third standard up the back is perfect then. We always like to come up with solutions that are not simple, but maintain the least amount of visual impact to the project.

[Dan Mages]

a third standard up the back is perfect then. We always like to come up with solutions that are not simple, but maintain the least amount of visual impact to the project.

I know, and I appreciate the effort to reduce the visual impact. However, the effort to do so it's more than I have time for. I'm hoping the standards will be hidden by the books and items on the shelves.

Will decorative trim along the front also work to reinforce the shelf? I can always beef it up with an extra piece behind it.

[Mike Cutler]

I did a little experiment this morning with a shelf standard and brackets from the Borg. I can install two of these on the back wall to prevent sags and use the clips on the side for additional support on the ends and along the front. I will also add a 4/4 x 2" poplar band to the front to the shelves. Will biscuits, glue and pocket screws be overkill??

Thoughts?

Dan

Dan
I personally think this will be enough. What is the rating on that shelf bracket?

Here's an idea for the future if you should want to integrate form with function. I think it would be to much work for you at this point with the shelves you're currently working on.
These shelves are 64" wide made of 5/4 jatoba. The two verticals in the middle have 1/4" drill stock, 8" long, recessed into the shelves underneath to hide the support. (This is where the strength comes from.)
A person would really have to work to load that book shelf more than my wife has. That thing is full.
It's been standing for some 12-13 years, so I must've gotten at least close to right.

http://www.sawmillcreek.org/showthread.php?10801-Finished-Project-and-a-question-Long&highlight=

[Sam Murdoch]

I'm surprised you haven't been able to find some more of the standards and clips already in use rather than the white brackets version.

Those metal standards with the clips don't need to be set into the wood. They can simply be screwed to the back and provide more than enough support. Especially if you set them to go all the way to the floor.

The draw back to the ones you are showing is that the standards stick out quite far from the back (may need to notch your shelves) and the brackets actually MIGHT interfere with placing books. I write "might" because they do have the benefit of serving as bookends too - in fact I think you can buy bookends to go with that system.

As for using biscuits (or Dominos) to attach your front edge - they make the work easier as they locate the top edges perfectly. Doesn't add much to the strength but surely makes the glue up easier. You can nix the pocket screws altogether but do use glue.

You are certainly solving the problem!

[Dan Mages]

I'm surprised you haven't been able to find some more of the standards and clips already in use rather than the white brackets version.

Those metal standards with the clips don't need to be set into the wood. They can simply be screwed to the back and provide more than enough support. Especially if you set them to go all the way to the floor.

The draw back to the ones you are showing is that the standards stick out quite far from the back (may need to notch your shelves) and the brackets actually MIGHT interfere with placing books. I write "might" because they do have the benefit of serving as bookends too - in fact I think you can buy bookends to go with that system.

As for using biscuits (or Dominos) to attach your front edge - they make the work easier as they locate the top edges perfectly. Doesn't add much to the strength but surely makes the glue up easier. You can nix the pocket screws altogether but do use glue.

You are certainly solving the problem!

The brackets that are used on the side are available at the Borg. I am concerned that they will only provide support along the back of the board allowing for sag along the front. I had this issue in the front closet. The 10" deep shelf was supported along the side and back, but had a generous dip in the middle. I had to add a bracket in the middle to help prop it up.

Mike Cutler. That is a beautiful shelf you built! I am not 100% sure on the weight load. Some of them on the Borg website list 100 lbs load per bracket.

[Ole Anderson]

Edit: Now rip the flanges completely off. If you used 1/2" ply, your beam is now 6" tall by 1/2" wide. I assume you assume the resulting beam would support virtually no load at all?

My dad, also a civil engineer, graduated in 1933 from MSU, quipped that when multiplying 2 x 2 on a slide rule some would get 3.99. In other words, not applying common sense to an issue. I can only presume the jesting answer of no beam strength was meant tongue-in-cheek. (Oops, I just noticed the "I assume that you assume").

[Malcolm McLeod]

My dad, also a civil engineer, graduated in 1933 from MSU, quipped that when multiplying 2 x 2 on a slide rule some would get 3.99. In other words, not applying common sense to an issue. I can only presume the jesting answer of no beam strength was meant tongue-in-cheek. (Oops, I just noticed the "I assume that you assume").

Tongue is firmly, and misunderstanding-ly in cheek.;)

Dan, sorry about the giant 'left turn' in your thread.

[Sam Murdoch]

The brackets that are used on the side are available at the Borg. I am concerned that they will only provide support along the back of the board allowing for sag along the front. I had this issue in the front closet. The 10" deep shelf was supported along the side and back, but had a generous dip in the middle. I had to add a bracket in the middle to help prop it up.



I wasn't suggesting those standards and clips on the back as the sole support. You certainly want to add the solid wood front edge too as has been discussed. Still no a bad idea to add a riser on the back of the shelf too (my first post in the thread). Makes for a rugged but clean looking wide span shelf system - after the fact. Before the fact, a middle partition would have been a better design.

[Dan Mages]

I wasn't suggesting those standards and clips on the back as the sole support. You certainly want to add the solid wood front edge too as has been discussed. Still no a bad idea to add a riser on the back of the shelf too (my first post in the thread). Makes for a rugged but clean looking wide span shelf system - after the fact. Before the fact, a middle partition would have been a better design.

That might work. I will have 2 standards on each side and on the back with clips and a beefy front edge along the front. The standards are only $3 and clips are 12 for about $2. I am going to rebuild these shelves this week and will share once it is done.


Tongue is firmly, and misunderstanding-ly in cheek.;)

Dan, sorry about the giant 'left turn' in your thread.
No worries! This place is great for getting the finest solutions to problems. In this case, I just needed the simplest solution.

[Dan Mages]

A two short school days and two sick kids have put me behind by about a week. The shelves have been modified to the best of my ability and prepped for paint. They were as straight and flat as well cooked bacon. :rolleyes: Hopefully, I will have them done by the end of the week. In the mean time, I have been thinking about lighting for this area. I am going to install a 4" recessed light with a gimbal fixture to wash selves with light. I am now trying to figure out the desk area. The alcove above the windows is 5" deep and 72" wide. The two options I can think of are a 3" recessed or a 2' light bar. Are there any other creative ideas?


The rabbit hole continues... I'll paint the room. But while I'm at it, new window & cabinet hardware, fix the heating, improve the shelving, improve the lighting, replace the floor...