How to reinforce a sagging shelf

Fixing your sagging shelf is an easy, budget weekend project

Too much weight and flimsy initial construction can lead to sagging and bowed shelves around the home.

As well as being visually unappealing, sagging shelves can present hazards. If the shelf breaks due to stress, the objects on the shelf can fall and could potentially injure people.

With all the busyness of daily life, it’s easy to put household chores and maintenance on the back burner. Thankfully, reinforcing a sagging shelf is a task you can easily fit into a spare few hours this weekend. We promise.


If you have to buy new tools, the shelf reinforcement could cost up to $100 in total. If you can borrow tools or have most tools on hand (except for Carinya’s shelving brackets), the total cost will likely be less than $20.

The tools you’ll need

  • Measuring tape
  • Pencil
  • Shelving brackets
  • Drywall anchors
  • Screws
  • Screwdrivers

Choosing brackets

There are several options to reinforce a sagging shelf. Carinya has a range of functional reinforcing brackets and plates, including:

    brackets and T-shaped brackets
  • Pressed reinforced plate brackets

The type of bracket you require will depend on the space between your shelves and the amount of weight you are looking to reinforce. A single floating shelf may only need a single angled bracket.

If you are unsure, contact the friendly team at Carinya, or visit your local Bunnings Warehouse to find out which brackets will suit your shelves.

How to install brackets

You can install brand new reinforcing brackets in a short amount of time and just a few easy steps.

  1. Measure the length of the shelf in order to determine the middle point. Mark with a pencil.
  2. If you have several floating shelves on top of each other, measure the distance between the shelves parallel to the sagging layer.
  3. Line the metal bracket to the centre of the shelf and mark these spots on your wall.
  4. After you remove the shelves from the wall, screw drywall anchors into the spots you’ve marked.
  5. Position the brackets over the anchors, screwing into the anchors and ensuring screws are tight.
  6. Replace the shelves, and you’re done.

Shelves can also be reinforced with planks of wood vertically along the wall, however this requires more tools and expertise.

Where to buy brackets

Carinya are bracket specialists, selling top quality brackets in Australia for more than 30 years. Carinya focus on supplying quality brackets using only the highest grade materials, so you know you’ll be reinforcing your shelves with the best product.

Their range of over 300 brackets means that you’ll always be able to find the right bracket for the job. Head into your local Bunnings Warehouse to view the range, or give the Carinya team a call on 1300 727 535.

Utility shelves are one of those wonderfully practical additions you can easily make to any garage or laundry room. Not only do they allow valuable storage, but they also display commonly used items while still keeping them organized. Unfortunately, these shelves often get overloaded and then become unsafe. To secure the utility shelf, you need to reinforce it with extra structural support to disburse the load. Flat steel connector plates are also referred to as flat steel repair plates. They are used to repair or connect furniture together and have multiple holes along a flat piece of steel. Any major home improvement store should carry these items in stock. If these pieces cannot be found, multiple types of reinforcement bars can be found on the Internet.

Step 1 – Identifying Problem Areas

Often you can visually see where the shelf is sagging. This sag normally occurs in the center of the shelf, but can be located off to one side or the other depending on the load. On the underside of the shelf, mark the place where the shelf is sagging and will need the support. If no sag can be found, measure the shelf and mark the center and the midpoints between the center and edges. Each marking should be reinforced to provide adequate stability.

Step 2 – Detach the Shelf

Remove all the items that are placed upon the shelf. Remove the shelf from its brackets and turn it over to locate the marking where reinforcement is needed. Line the holes of flat steel connector plate up to the markings and secure with a wood screw to the shelf. The steel plate will better disburse the weight of the heavy items on top. However, if the load is particularly heavy, place one flat plate connector above the marking and one below. Make sure the screw does not penetrate the other side of the shelf. If it does, sand the tip down so it will not be unsafe.

Step 3 – Remounting the Shelf

The triangle brackets provide greater structural support because it redirects the force back to the wall. However, this means the utility shelves must be properly mounted to the wall for structural safety. Locate the studs within the wall to mount the shelf. If mounting into a different material, be sure to have the appropriate fasteners. Switch out the previous shelf supports with the triangle brackets and remount the shelf. Be sure to check for level. Take an additional triangle bracket and secure it through one of the holes in the flat steel connector plate and up into the shelf. The sagging portion of the shelf should now have not only the steel connector plate to help disburse the weight, but also the additional triangle bracket for support. Use additional triangle brackets to secure the shelf midway between the reinforced area and each end of the shelf.

I’ve been meaning to write this up for awhile. We did this over a year ago, but I thought the internet might appreciate this how-to.

How to: Reinforce a Crappy WalMart Bookcase OR How to Fix Sagging Shelves

When Orion and I bought a bookcase from Walmart, we bought it because we wanted to store our books on it. The low, low $35 price tag should’ve tipped us off to its obvious shortcomings, but I’m sure this mistake has been made many a time before. The shelves, made of weak particle board, started bending in the middle immediately, even when we kept the actual books towards the edges of each shelf. Note the sagging:

So if, like us, you would like your bookshelf to actually be able to hold books, go through the following steps.

You will need:
One crappy WalMart bookcase.

3″ wide board, cut to the height of your bookshelf (floor to top)
4 L-brackets, the color of your bookshelf (these will be visible)
Screws to secure the brackets* (See Very Important Footnote)
Six 1 1/2-inch screws to secure the board
A Drill

The extras all cost us about $20 at Home Depot. Not too shabby.

First, make sure your board is the exact height of your bookcase, floor to top. If it is the wrong height, you might throw your bookcase off balance, which would be bad.

Part I) Securing the board to the back of your bookcase
1. Remove shelves from bookcase
2. Place bookcase face down on floor, so that the back of the case is up
3. Place board on top of the bookcase in the exact center


Thanks for the great idea, now I know what to do with my 3 crappy wal-mart bookshelves!

Looked all over youtube for this tutorial but never found it. I was wracking my brain, and thought doing something like this might reinforce my sagging OfficeMax. Thanks sooo much for a user friendly tutorial!

Thanks for the tip. Also have 3 of these things and this modification is working out great so far.

One other thing people might want to take note of. pay attention to the size of the screws you're going to attach the L-brackets with or you might end up screwing the bookshelf into the floor (almost happened!)

or at the least, you'll have a bunch of nasty screw points sticking out of the back.

Good tip! Definitely don't want a bookshelf attached to your floor.

What is it with people named "Anonymous" having three of these? 🙂 I also have three crappy sagging bookcases. filled with books, of all things, and they don't seem to be handling it well; why call them bookcases in the first place, I wonder. I plan to do this as soon as I can borrow someone to use my drill for the day (I hate power tools).

And yes, check the size of the screws; attaching your bookcase to the wall is not recommended, particularly if (like me) you're renting.

A very comprehensive DIY, indeed! Congratulations for making the bookshelf "not-so-crappy" anymore. Organising books has never been this convenient. Nevertheless, this article is very helpful. Glad you've shared this. Please keep posting your thoughts in the future. Ciao!

Hi Betsy and Orion,
My friend and I just reinforced my 2 new crappy bookshelves from Walmart by following your directions! Just wanted to say Thank You so much.
Ben in Kansas

Hi Ben! Great to hear that this was helpful for you, you're welcome and thanks for the comment 🙂

Yes, it worked great! I had screws that were too long for the brackets and nearly did the same thing.

This comment has been removed by the author.

I'm going to do this for 19 of these. (I've been putting together a library since 1971, and my money is in the books.) I need to know what size bracket because I'm going to be ordering 95, and I don't want to make a mistake. Can you tell me what size you used?

Hi Tom, your library sounds like it's going to be amazing and full of heavy books, I picture a rolling ladder like the one in Beauty and the Beast, and I therefore ask that you promise to roll around singing at the top of your lungs when you finally finish your epic book setup!

I very much regret not writing down the exact specs of the items I used, but I didn't get around to actually writing up this post until a year after we had fixed up the bookcase and by that time I simply couldn't remember. However, we still have this bookcase (and not a single sagging shelf – self-five!) so I got out my tape measure, and here is what I found:

The L Brackets are 7.5 inches on one leg and 5 inches on the other. I put the 7.5 inch side along the bottom of the shelves and secured the 5 inch side to the back-board.

The exact measurements of the brackets are not all that important, just so long as the leg that will support the shelf does not exceed the depth of your bookcase (or it will protrude) and the base-board leg does not exceed the height of the shelf beneath it. I picked my L brackets because they were the only ones that looked about right at Home Depot that day.

A quick note that other commenters have brought up: make sure the screws you use to secure the bottom leg of your bracket to the back-board do not exceed the thickness of the board. The board I used was about an inch thick and the screws that came with the bracket were about 3/4 of an inch long, so it worked out well for me. Just a note of caution so you don't secure your bookcase to the floor, although the shelves probably wouldn't sag that way either. But then again, not so great for rolling ladder conciertos. Best of luck to you!

How to reinforce a sagging shelf

By Johnt007871 Follow

How to reinforce a sagging shelf

How to reinforce a sagging shelf

How to reinforce a sagging shelf

Everyone has seen book shelves that seem to defy physics and bow until they almost touch the books on the shelf below. This is a simple fix to extend the life of your bookshelf and help keep your OCD for straight lines in check.

I performed this fix on our bookshelf which also has a TV in it. The fix is less ideal for shelves above eye level because the reinforcement will be more obvious unless you paint it.

Step 1: Intro and Materials

For this fix you’ll only need a couple things.

Aluminum C or U channel or similar

Hacksaw for cutting metal, or similar

Step 2: Clear Shelf

Remove all books and objects from the shelf.

Measure the width of your shelf.

Step 3: Remove Shelf

Remove the shelf

Cut Aluminum C channel the same length as your shelf (or a hair under, but not longer)

Step 4: Add Reinforcement

Place the C channel on the pins that hold up your shelf. I only put it on the back where most of the weight is, but if you have deep shelves or many heavy books then you may need to reinforce across both sets of pins.

If your C channel is too long, try to cut off a little or use a file.

Step 5: Replace Shelf

Put the shelf back UPSIDE DOWN if you can. This will allow the sagging and bowing to flatten back out from the weight of the books on top.

I added a red line so you can see the bow.

Step 6: Replace Books and Bask in Glory

Replace your books! Take the chance to organize them by series or theme or what not.

As hacks go, this is an inexpensive solution to a common problem. Billy bookcase shelves have a reputation for sagging. It’s easy to strengthen the shelves with this hack. How much more weight can the shelves bear? I don’t know, but mine were holding full and even double-shelved text books with no problems.


  • Hacksaw or metal cutting blade of some sort
  • File to smooth the cut ends


  • Aluminium “U-channel” strips from the local home improvement store (One 8-foot strip can stiffen three 30-inch shelves.)
  • Billy bookcase or other shelves you want to reinforce.


  1. Take a shelf with you and buy a channel that snugly slips over the shelf edge.
  2. My Billy shelves used 3/4 inch channel, but test before you buy.
  3. Cut the channel into pieces about 6 inches shorter than your shelf.
  4. Use the file to smooth the rough edges on the cut ends.
  5. Slide the channel over the back edge of the shelf, center it, and place the shelf on the pegs.

How to reinforce a sagging shelf

How to reinforce a sagging shelf

Q: How was this hacked or put together?

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9 Responses

I bought 3/4 inch u-track at Lowes. It was a very tight fit over the shelf. I used 2 crescent wrenches to spread the track at one end and the tapped the track onto the shelf with a rubber mallet.

Does this solution work if you want to mount oxberg doors as well? I mean do the shelves stick out so as to prevent mounting?

This was my submission:
To those concerned about “cheaping out”, and cutting the channel too short, we discussed full-length versus slightly shorter but less wasteful lengths, and did the engineering calculations. Chandru is right. The unsupported 3 inches at either end are insignificant compared to the 24 rigid inches in the center.

It’s perhaps also worth pointing out that if you had the aluminium channel the full width of the shelves, you may have difficulty sliding in the back section. Leaving it 10-15mm short at each end means this isn’t an issue.

Cutting the channel short is Bad Advice. Cut them the full length of the shelves. Toss the 6″ length of leftover C channel. You cheaped out to start with when you bought an MDF product, don’t cheap out as well on “fixing” it.

Of course by the time you do all this, you might as well have just bought the Hemnes solid wood bookcases to start with.

If you must buy Billy bookcases, stick to the narrowest versions. The shorter an MDF shelf is, the less likely it is to sag. You can’t even attach a support rail for the shelves to the back of the bookcase because the backing is basically cardboard.

Bypassing MDF doesn’t necessarily cure a sagging problem. A combination of hardwood and shelf design is needed, which is difficult and expensive to come by in practice. Heaven help you if you want style with that. The expense gets quickly out of hand the more shelving that is required.

The Hemnes shelves are made from pine wood. At this moment, I’m staring at a pine wood book-case, constructed exactly like the Hemnes, which is sagging. Finished soft wood shelving isn’t worth the money in my opinion. Reinforced MDF is fine for cheaper shelving, or pay the money for hardwood imo.

No really… why did you cut them 6in shorter than the shelf.

My guess is to to save on the number of aluminum strips to buy. One 8-foot strip = 96 inches. If you cut into 30-inch pieces, you have a 6-inch piece left over. If you cut into 24-inch pieces, you have four pieces and no left overs. Also, you only need four pieces because the center shelf is not removable.

Actually, if you know about mechanical stress, the highest is at the center, tapering to zero at the very ends. So it’s most important to reinforce the center; leaving a short gap at each end makes no difference.

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I am working on a job that requires some shelves 12″ x 50″, and I don’t want them to bow. The shelves will be used for mainly photos, but some books as well. I was planning on gluing 3/4″ and 1/2″ ply together, or 2 layers of 3/4″ and putting on a hardwood edge, hoping this would be enough.

Then I started thinking, with all the labor to make these, would it just make sense to make the shelves out of solid wood, poplar or soft maple, 6/4 stock? I suppose the solid wood has more strength, but could have a tendency to warp. Just wondering what others have done. I know I don’t want to use Medex or MDF, as I have seen it sag over time on other job sites I have been to.

Forum Responses
(Cabinetmaking Forum)
From contributor T:
I have offered this suggestion before, and been soundly criticized for it. It does, however, work. Take two pieces of 3/4 plywood and run them through the planer, removing the top layer of veneer. This will cause each piece of plywood to develop a severe crown where the core is exposed. If you re-glue these pieces of plywood back together with the bowed faces opposing each other, you will produce a pre-tensioned plank that is dead flat. With a 1 1/4 inch thickness you should be able to do chin-ups on 50 inch length without any deflection.

From contributor R:
50″ long shelves do need reinforcement and solid wood would be better than plywood. A good combination would be to use 3/4″ with a 3″ front edge splined or rebated to the edge of the shelf. The 3″ front could also be from 3/4″ hardwood. If you use a thick shelf for that span that will work also but I’d suggest 8/4 for poplar or soft maple.

From contributor L:
If you take two 1/2″ pieces of ply and use 1/4″ blocks on the inside going from front to back, you will create a torsion box. Laminate some solid stock on the front and back and it will resist quite a bit of weight before a bow might form. I think it would be cheaper in the long run to use solid stock, less labor.

How to reinforce a sagging shelf
Click here for higher quality, full size image

From contributor P:
Have you tried the sagulator in the software connection on this site? I have had good luck with it.

From contributor N:
You guys are over-engineering this shelf. 3/4″ plywood and 1 1/2″ solid wood edgebanding. For what he’s doing, it will last for years and years. Unless he’s going to use it for loading a motorcycle on a truck from time to time when he can’t find a ramp, I wouldn’t worry about it.

From contributor S:
You took the words right out of my mouth. I’m going to go out on a limb here and tell the questioner to add a 1 1/2 strip to the back, too, if he is that concerned.

From contributor N:
With the extra 1 1/2 strip on the back, you could use it as a ramp to load a motorcycle.

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My TV stand is a Sauder #413010 (specs here). The top shelf has started to sag, as you can see. The TV is a Sony KDL-55W800B which barely weighs 40lbs, whereas the shelf is spec'd for 95 lbs.

I am thinking of buying a new TV which weighs almost twice as much (79 lbs, still below weight limit) and am worried about the sagging. What would you do to reinforce it? I was thinking of some metal channels to somehow reinforce the top shelf (how?), or maybe metals straps across the back. Grateful for any suggestions! Thanks.

What about covering the entire top with a piece of tempered glass to distribute the weight more evenly?

That sounds like a good idea actually. But where would I get a 47¼" x 16¾" sheet of tempered glass from? I thought it can't be cut.

Perhaps call the manufacturer. Sounds like you are under their specified weight limits and it is still flexing.

If that does not work .

I see two issues: 1. fixing existing sag 2. prevent additional sagging.

For #2, adding tempered glass to distribute the load as suggested by Aldermere will probably work.

For #1: I can't tell what the top material is made up of, so that complicates it. In straightening up the bow you may break the top (assuming it is particle/fiber board). I do like your own suggestion of metal rails mounted under the top spanning the gap in the middle where all your electronics live.

Accommodates up to a 47" TV weighing 50 lbs. or less

That is info from the link you provided. If you have documentation from Sauder suggesting otherwise, I would call Sauder. Also, depending on the age of the stand, you might be able to return or be under warranty with Sauder.

I would get a piece of mdf or plywood for the top and cut it to size, Get a new tv stand or mount the tv to the wall before I modified anything.

That is info from the link you provided. If you have documentation from Sauder suggesting otherwise, I would call Sauder.

Hmm, where did you see that exactly? On the web page I see 95 lbs for the top. And here is the appropriate page from the manual that says the same.

I've sent Sauder an email anyway.

I would get a piece of mdf or plywood for the top and cut it to size

And how would you attach it to the top?

Looking a bit more at your picture vs the TV .. I really don't see how that TV caused the warp. The TV's stand is distributing the weight away from the center of the TV stand. My best guess is something else caused that warp or it was that way when you purchased it.

I'm guessing this unit is made particle board? It has very little structural integrity. that's why this type of stuff is so cheap. Anyway. It's a little hard to tell exactly what's going on from the pic but I think the whole thing is sagging. Meaning the bottom panel as well as the top. That amp must be heavy. Check the measurement from the floor to the underside of the bottom panel at the ends of the unit. Then check it in the middle. Is it different? Is the difference reflecting the sag in the top? The easy fix is to cut two pieces of wood or something to what the height should be. Position them underneath where the two interior partitions are. If you have no wood or the means to cut it, just stack up some old books or something. The idea is simply to provide support for the two interior partitions which should then provide better support for the top. Good luck.

I'm guessing this unit is made particle board? It has very little structural integrity. that's why this type of stuff is so cheap.

Yup. I would have been happy to spend more, but this was the only TV stand that had the space and shelves that I wanted.

Anyway. It's a little hard to tell exactly what's going on from the pic but I think the whole thing is sagging. Meaning the bottom panel as well as the top. That amp must be heavy.

I think you're onto something here! I scanned in the page from the manual that describes the various weight limits, here. My receiver, a Denon AVR-S900W, weighs 21 lbs. I'm not sure what "50 lbs total" is supposed to mean but if it means the combined weight on all the shelves in the centre section, then I should be within spec – the next heaviest item is an Aiwa MX100 VCR which according to Amazon weighs 11 lbs. The only other devices are a cable box (under 10 lbs) and a slimline Blu-ray player.

Of course, regardless of specs, some sagging is happening.

Check the measurement from the floor to the underside of the bottom panel at the ends of the unit. Then check it in the middle. Is it different?

Yes it is! By about 5mm.

The easy fix is to cut two pieces of wood or something to what the height should be. Position them underneath where the two interior partitions are. If you have no wood or the means to cut it, just stack up some old books or something. The idea is simply to provide support for the two interior partitions which should then provide better support for the top. Good luck.

I'll give that a try. Thanks a lot for your help. And to everyone else in this thread for your replies!

Our liquor cabinet has the usual row of holes drilled on either side for height-adjustable shelves, with typical shelf pins:

How to reinforce a sagging shelf

I think the wood is MDF + veneer. It might be plywood. It’s not holding the pins very well.

How to reinforce a sagging shelf

The end result was sudden catastrophic failure followed by two hours of mopping up glass shards while trying to convince the world-famous Siberian husky who lives with us to stay in the other room.

How to reinforce a sagging shelf

Yes, that is a marble tabletop that actually got shattered into pieces by a bottle of Maker’s Mark (recommended).

What would you use to reinforce these shelves instead of the dinky little pins?

How to reinforce a sagging shelf

5 Answers 5

The type of shelf pins shown in your photo are able to twist out of crappy MDF or particle board side walls when a lot of torque is placed on the pin due to excessive weight placed upon the shelf. There are alternate types of shelf bracket pins that are designed to keep the pin at 90 degrees to the side wall thus keeping it from torquing out of the hole. Here is a picture of one type that I have used in the past with good success.

How to reinforce a sagging shelf

You should be able to easily use your existing cabinet and bracket holes with this alternate type of bracket. The old pins broke out the side wall at the top of the hole and these will rest on the bottom of the holes once installed. You may have to push some of the splintered wood flat but then you would install these brackets up tight to the side walls. The shelf will then sit on top of the part of the bracket with the hole. It is best if the side to side length of the shelf fits snugly between the bracket at each side. Once you have the brackets and shelves in place you screw the bracket to the bottom side of the shelf. It would be highly encouraged to drill a pilot hole for these screws . but be careful to not let the hole or screw come through the top of the shelf.

It is the fastening of the bracket to the shelf that will provide most of the force to keep the pin straight into the cabinet side wall.