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Reducing thickness of 1 1/2" particle board to lighten a countertop

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Forum topic by jkjames posted 06-19-2018 02:35 PM 2891 views 0 times favorited 18 replies Add to Favorites Watch
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jkjames

13 posts in 2462 days


06-19-2018 02:35 PM

So let’s just say there’s a new project afoot at my house, to use an Ikea particle board countertop as a desk surface. Good idea from the position of durability, but not from a perspective of weight. It is 1 1/2” thick with a 1/8” hardwood top layer. 74” x 26”, 1 1/2” thick and about 63 lbs. It is finished on the top and all sides. They call it Karlby.

The problem is that the desk is of the standing desk variety, with stepper motor-driven legs for height adjustment. It has a total weight limit including desktop stuff of 60 lbs.

To meet the weight requirements, I think I need to reduce the weight of the slab by 50%... and the only way would be to route out 50% of the meat of the slab from the bottom.

So my question is:

Would I damage the integrity of the slab too much by routing out 3/4” of the slab from the bottom and in essence leaving a 3/4” slab at the end with will thickness around the edges to support the edge finish??

(My first thought is no since 3/4” particle is still pretty strong…).


18 replies so far

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jonah

1781 posts in 3354 days


#1 posted 06-19-2018 02:52 PM

A 74” wide sheet of 3/4” particle board would need a hell of a lot of support to be strong enough to serve as a desk top. Why not upgrade the legs, rather than trying to monkey with the top?

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jkjames

13 posts in 2462 days


#2 posted 06-19-2018 02:58 PM

The desk legs are motorized and $600… they are heavy steel. They can handle way more than 60lbs, but the motors cannot.

I am currently using Baltic Birch 60” x 30” x 3/4” and its working fine.

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Rich

3204 posts in 645 days


#3 posted 06-19-2018 03:03 PM

You could remove a lot of the weight without significantly sacrificing strength by drilling out an array of holes with something like a 2” Forstner bit. It would be pretty tedious, but should do the job. Space them maybe every 3 inches and be careful not to drill through. That’s pretty easy with a Forstner bit, since they provide a fairly solid visual reference to the depth.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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JayT

5731 posts in 2267 days


#4 posted 06-19-2018 03:18 PM

I’d leave some full length “ribs” and route out smaller pockets in between. That should help preserve the strength, as you would only have small sections of 3/4 in between supports of 1-1/2, while still cutting down the weight considerably. Something like this:

-- In matters of style, swim with the current; in matters of principle, stand like a rock. Thomas Jefferson

View Bill_Steele's profile

Bill_Steele

362 posts in 1787 days


#5 posted 06-19-2018 03:37 PM

Drilling holes (per Rich’s suggestion) sounds like a good idea. Alternatively, instead of routing a 3/4” recess in the bottom of the slab leaving a 1.5” border—you might route channels—in an effort to leave something that will provide more structure/support. I’m not sure if this is any more structurally sound or stiff than the “hole” approach or what you outlined.

If you need something light and strong you may consider saving the slab for another project and trying something similar to this table top.

I made this folding table about a year ago and it consists of a 1/4” plywood skin with a pine border (3/4” thick) and for structural support there are I-beam like supports glued to the 1/4” skin. It’s very light—the whole table weighs less than 25 pounds (including the legs). Here is another picture that shows what I’m talking about a little better. Ignore the painters tape and support blocks—they are only there for the glue-up.

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Bill_Steele

362 posts in 1787 days


#6 posted 06-19-2018 03:39 PM

I was trying to say what JayT posted—he did a better job of explaining it.

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Rich

3204 posts in 645 days


#7 posted 06-19-2018 03:47 PM

I like JayT and Bill’s ideas better than the Forstner bit. That was the first thing that popped into my head, but the router cuts will be far easier to execute.

I think, regardless of what pattern you choose, leaving ribs in both directions is important for stiffness and strength.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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clin

882 posts in 1052 days


#8 posted 06-19-2018 04:21 PM

Even 1 1/2” particle board may not be thick enough to support at just the ends. You have not described the base and where it supports the top.

For example, countertops are often made from particle board. Usually 3/4” with edges and cabinet contact points doubled to give it a 1 1/2” look. But countertops are usually supported all across the backs and fronts and every 18”-36” inches front to back (by the cabinet sides).

While I think it might be possible, it really depends a lot on the way the base supports the top.

Now, if you have to make this work, here’s one way to do it. Remove as much material as you can. Perhaps leaving just 1/2” of the top. Leave full thickness as ribs on about a 6” grid. These ribs only need to be 1/4” or so thick. Then skin the bottom with 1/4” plywood or similar. This will make the unit into a torsion box. This will be very stiff and possibly even stiffer than the original top. Mostly becasue it will be 1/4” thicker.

It’s key that the skin be well glued to all the ribs. Most of the work is in removing the material. So if you’re going to do that, adding the skin is trivial. Be sure the top is flat when you glue the skin on, becasue whatever shape it has when the skin is attached, is the shape it will have.

Of course this skin will show at the edges, but you could cover this somehow. Or route it out such that the skin doesn’t go all the way to the edge and would not normally be seen.

I think you could remove about 90% of the surface area to a depth of 1”. So you would be removing 1”/1.5” * 0.9 = 60% of the material. This should get in in the range 24 lbs. Then you need to add the weight of the skin. I think 1/4” plywood is in the range of 1/2 to 3/4 lb per sq-ft. So your top at about 13 sq-ft would be 6-10 lbs of 1/4” plywood. I think you could even go to 3/16” thick.

Of course leave full depth at your mounting points.

-- Clin

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CaptainKlutz

321 posts in 1550 days


#9 posted 06-19-2018 09:36 PM


I am currently using Baltic Birch 60” x 30” x 3/4” and its working fine.
- jkjames

+1 all above posts, Supporting top properly is key to success, even for full thickness particle board. Will need to be careful in design.

hmmm…..
If BB ply was working OK for you, and you wanted a nice wood finish; why not just add veneer plus edge banding to existing top?
These 2 items should be less work than machining weight out of a 6 feet piece of particle board.

FWIW – Karbly wood countertops are nothing more than veneered particle board. (found out hard way, it is cheap low strength medium density stuff as well)
IKEA stopped carrying many of the different solid hardwood countertops they used to sell and moved to veneers. Believe Hammarp is only one made from hardwood today. In past, used several of IKEA solid maple and beech countertops for workbenches, and kitchen island projects (was cheaper than buying maple lumber here in AZ). Do not like that only solid top they sell now is Oak, as Oak has large open grain and does not make a good cutting board surface in kitchen. But I digress off topic….

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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BroncoBrian

617 posts in 2014 days


#10 posted 06-19-2018 09:56 PM

Bill, do you use this folding table to sell lemonade or for glue-ups. It is a great design and seems like it would be easy to fold and hang on a wall. Workspace like that is lacking in my shop, this would be very helpful to have available. Would you like to ship it to me, or should I build one?

-- I saw a guy wearing a leather jacket at the same time he was eating a hamburger and drinking a glass of milk. I said "Dude, you are a cow. The metamorphosis is complete."

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jkjames

13 posts in 2462 days


#11 posted 06-19-2018 09:57 PM

I like the torsion box idea. I understand that concept well.

The Ikea countertop is 1.5” thick… the wife likes the chunkiness of this look, and she wants to make two other work surfaces in the room that would match. Those pieces there is no concern about weight.

I was leaning towards edge-banded 3/4” or 1” ply myself, but one has to take all things into consideration. I like my 3/4” Baltic Birch top with a bullnose… it’s easy on the forearms.

I am 200 miles from the nearest Ikea and I have to go to that area for work tomorrow.

View Bill_Steele's profile

Bill_Steele

362 posts in 1787 days


#12 posted 06-19-2018 11:21 PM

BroncoBrian, I think you should build one—I’m sure you’ll enjoy the process :). I wish I could claim the design as my own but I got that from ShopNotes issue 98. It has turned out to be a versatile table that folds up nicely and is easily stored up against a wall or could be hung up.

There are handle cut-outs on each side to make carrying it easier. The underlying support structure makes it very strong and it will support a few hundred pounds without much fuss. I use it for extra work space as needed. I made it a little taller and made the cut-outs in the support “beams” large enough to fit closet rod—so if I use it with my miter saw I can have a few pieces of trim close to the saw.

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woodbutcherbynight

5290 posts in 2464 days


#13 posted 06-20-2018 02:09 AM

The torsion box method is best weight ratio of all that have been mentioned. Also since you say you want to have 2 more it is a repeatable process. In making it you can account for where the legs mount to the top and support those areas while leaving others open like a hollow core door. If you are worried about flex you can always mimic a hollow core door design and cut cardboard to width and zigzag across the open areas. Little hot glue and it will stay in place.

-- Live to tell the stories, they sound better that way.

View LiveEdge's profile

LiveEdge

589 posts in 1676 days


#14 posted 06-21-2018 08:52 PM

I think you are asking for trouble. Particle board is nowhere near as resistant to sag and rupture as hardwood. I found a PDF which compared various particle boards and the modulus of rupture. The values were about 2,800 to 3,200. By comparison, red oak’s value is 14,000 and Hickory is 20,000. The reason your Ikea counter is 1.5” thick is because that’s what is needed.

I’m not an expert though so just take it as advice. My initial question was why you are taking $600 legs and trying to marry it with a cheap, sub-optimal top?

View DS's profile

DS

2931 posts in 2476 days


#15 posted 06-21-2018 09:04 PM

You might be surprised at how much office furniture is made from corrugated core plywood.
Super strong and lightweight.

Yes, it looks like cardboard, but it can withstand about 200psi.
Laminate the front and back with your favorite material – veneer, HPL, hardboard, etc – and you are off to the races.

Plan on about $60 to $65 for a 1 1/2” x 4×8 core – not really cheap at all, but will fill the bill nicely.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

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