Just Glue, or Glue and Screw?

[drw]

I am in the process of building bunk beds for my grandsons. My daughter-in-law provided me with a set of plans, The plans call for the bed posts to be made from 4"X4" boards, however, since I could not find any hard maple in that size I glued two 2"x2" boards to achieve the required dimensions. With this information in mind, is glue (Tite Bond lll) sufficient or should I reinforce the posts with screws?

Thanks for your input.
Donn

 

[Steve_Honeycutt]

Donn,

I was reading today on Wood Gears (www.woodgears.ca) results of tests showing which wood joints are the strongest as well as which glues are the strongest. This might give you some ideas.

Steve H.

 

[MarkE]

I would think 2" boards face glued together with Titebond III would be plenty strong enough without screws.

 

[cpw]

I would think 2" boards face glued together with Titebond III would be plenty strong enough without screws.

+1. If both faces are flat so they mate properly and you clamp them until the glue is dry the wood will tear before the glue joint fails.

FYI: Glue does have a limited shelf life, so if it's been around for a while you might want to check it.

From Titebond's FAQ:

[h=4]What is the shelf life of Titebond Wood Glues?[/h] Our literature states the shelf life of all of our glues as one year. Titebond Liquid Hide Glue includes an expiration date on the bottle, because it can progressively lose its ability to dry hard, and this change is not visually obvious. Titebond Polyurethane Glue has a one-year shelf life in an unopened container, but is useable as long as the glue remains fluid. Polyurethanes, however, are designed to react when exposed to moisture. Sometimes, they begin to cure, and solidify, after the bottle has been opened. Most of our yellow and white glues, including Titebond Original and Titebond II, remain usable beyond two years. Should Titebond Original become thick and stringy, or Titebond II turn into an orange-colored gel, these changes signify that the glue is no longer usable. The minimum shelf life of Titebond III is stated as one year. When stored appropriately at room temperature, Titebond III is expected to last beyond its stated shelf life. If thickened, shake vigorously by firmly tapping bottle on a hard surface until product is restored to original form.


[h=4]What does the term "shelf life" mean in regard to Titebond Wood Glues?[/h] "Shelf life" is a conservative estimate of the minimum time period that we would expect a given product to remain usable, when stored as directed. This concept might also be called "useable service life" or "storage life," and it necessarily refers to both the physical handling properties and the ability of the product to perform properly. When used in reference to wood glues, reaching the stated shelf life does not mean that a product will "expire" or become unusable. Instead, we view the stated shelf life of most of our glues merely as a guideline to avoid potential aging concerns. In reality, as long as products like Titebond Original, Titebond II and Titebond III remain fluid, without a drastic change in appearance, they will continue to perform as intended.



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[BSHuff]

how are you taking 2 2X2 boards and making a 4X4?

If you face glue or laminate pieces of 4/4 or 8/4 together to make a 4" think piece of for the posts it will be gorilla strong. You are gluing long grain to long grain, and that makes a very strong joint provided you have a good joined surfaces. I would not use any mechanical fasteners in this instance except maybe a few at each end in the waste to keep is straight during glue up.

 

[Berta]

I have built a bed and glue will be fine used in this manner. (face glue).

Berta

 

[drw]

Thanks to all for your comments, I am very appreciative. Indeed, the post boards are face-glued and the glue is well within its expiration date. With respect to the process, I started with 8/4 stock, planed, jointed and dimensioned. The resulting posts are not exactly 4x4, more like 4X3.25, but all are the same and they look really good...I just want to be sure they hold up under the stresses of use.

Again, thank you for your comments!
Donn

 

[bluedawg76]

Those are some serious legs...4x4 hard maple

to clarify, 2 2x2's glued together equal 1 2x4, right? whereas 2 2x4's would give you the required 4x4, no?

 

[drw]

Sam, I stand corrected...you are right. I started with 8x4 stock, which I dimensioned to approximately 2x4 boards and then glued these to get the posts. You are also right about them being "serious legs".

Thanks,
Donn

 

[mkepke]

A glue-up will be fine if you use a decent glue and take some basic care with the glue-up.

Obviously I haven't seen your design, but if these glue-ups are corner posts, then the (massive) glue-joint will have little to no shear on it anyways, since I'd expect all the boards in the glue-up to run continuously from the top of the post to the bottom. In other words, you could use a couple of nails to hold the boards together and joint strength wouldnt be an issue.

My kids aren't old enough for bunk beds yet, so I made them twin beds that can be stacked when the time comes. The corner posts are made of humble 2x SYP glue-ups. The beds have been in service for a year and counting.

-Mark

 

[ehpoole]

The one question I have seen hinted at but not directly asked (unless I missed it) is: were all of the glued faces properly face jointed flat and square *before* the glue up? Then, were each of the now 2x4 sections face jointed before they, too, were glued together to form the final 4x4?

I ask the question because if someone is using 2x2's where most of us would have likely used two 8/4 boards that were cut into 2"x4" pieces for the glue up, then this may very well be store-bought S4S stock (such as that sold by the BORGs) that may or may not be perfectly flat and square by the time it is ready for use (and more often than not isn't). It is also difficult to precisely align four 2x2 sections during glue up, so assembling them into 2x4 pieces, face jointing the 2x4 sections to remove any alignment errors, then gluing the two 2x4 sections together -- and, if needed, face jointing and thickness planing the fully assembled 4x4 to eliminate any error and hide your glue lines.

If the face jointing was skipped, then it is a bit more iffy as to the quality of the glue lines because there is a far greater likelihood of voids within the glued assembly. If so, unless a good gap-filling glue (such as epoxy) was used, there will be weaknesses within the boards that may, or may not, allow for future delamination depending upon the forces being exerted on them. (For instance, a horizontal bolt with a heavy vertical load that is inserted dead-center in the vertical 4x4's will be concentrating it's vertical load in a manner that could cleave a weak glue line -- something you would not need to be concerned with if it were a strong glue line.)

Otherwise, if all faces were properly jointed and clamped tightly during the glue up, there there is little reason for concern so long as you were using a good-quality modern glue (which Titebond-III is).

If you question the quality of the glue up, then you might want to screw them together (you would need four screws each joining one 2x2 to its neighbor at 3, or so, points along the post's length). Ideally you would recess your screws so that you could then use grain-aligned tapered plugs to permanently hide them from view. If the plugs are cut from extra boards from your stock and chosen for matching color and grain similarities then the plugs will all but disappear from view when you are done.

 

[pviser]

I agree with my colleagues above regarding the adequacy -- with much room to spare -- of glue alone in the circumstance described. One could argue that two 2-inch thick boards glue together as a laminate would even be superior to a single 4-inch thick board: stronger and more dimensionally stable. One further point is that made by Brian above. Use a pneumatic nailer or some other mechanical fastener in two or three spots so you don't go crazy playing slippy slide as you are trying to clamp the boards together!

 

[bluedawg76]

just to add: my workbench top is 72x30", 3 1/4" thick syp (~170 lbs) and is supported on ~4 1/4"x 4 1/4" syp legs which were face-glued (jointed/planed first of course) from 3 2 by's w/ titebond 2. these are m/t into the top (no glue, just weight and friction) i do all sorts of pounding, hammering, chiseling, planing, etc (i.e. downward and tangential/shear forces) and those legs easily support the weight and abuse. So as long as the bed rails/undercarriage are properly fastened, the legs will not be the weak point in the equation. good luck!

Sam

 

[Tarhead]

Titebond 3 will leave a dark line. Not what you want with Maple. Fresh Titebond 1 or 2 or white/yellow generic carpenter's glue will work great with long grain to long grain joints. No advantage in using the expensive stuff since it will not be exposed to outside conditions and there is a big glue area. Focus on getting the glue faces as matched and as perfect as you can. Any small gap will be hard to hide.

 

[Willemjm]

LOL, after reading your post, I had a dream last night that all my woodworking joints are starting to pull apart.

Personally, I avoid hardware, being screws, brads, nails, staples on all my projects wherever possible and use only joinery and glue. Titebond tests approach 4,000 psi, whereas Hard Maple only has a tensile strength of around 750 psi.

 

[drw]

Thanks again for sharing your insights and perspectives. Based on all of your comments I have become comfortable with just glue. I'll post pictures when the work is completed.

Donn