built up beam

[Jumpinfrog]

I am constructing the built-up beams for the 20 x 30 according to instructions on home page. I have staggered the joints on all 2x and plywood. The question is if I pin these together using Fastap #10 5" exterior screws instead of nails on both sides, is it possible to leave the glue out? I know the glue helps to solidify everything but with screws pulling the beam tighter together, will this work? What would be the spacing on these screws?

[John Raabe]

I would trust the opinion of some of the more experienced builders here, but I would guess that screws 6" o/c staggered at top and bottom of the beam would about match the strength of a continuous beam. But glue and nails would be cheaper and faster. And because it would be easy to do twice as many nails, the working surface area between wood and metal might be even more than with screws.

[John_C]

Here is a link where you will find pdf downloads for lots of beam, header, rafter and joist applications.  Many of these are very detailed and basically are an aid to sizing things when doing a detailed load trace.  The Headers and Beams ref.207  for example is 36 pages.

http://www.raisedfloorliving.com/publications.shtml

The short answer, as I understand it, to your question is that there is enough of a fudge factor in simple tables to cover some variations.  A true laminated beam would be done like a glue lam with no voids and the glue joint being stronger than the adjacent wood fibers.

[Jumpinfrog]

500 of these screws fell into my lap. I figured this was the best point of the project to use them. Figuring they were screws and better than nails, I would just assemble the built up beam without glue. No cost, no hassle with the glue. I just wanted to be sure that everything would hold together without the glue. I however built 3 beams and with 6" spacing on all 6 sides that would total around 750 screws? If I buy 250 more that will cost about $100 total. I believe that would still be less than nails and glue? What type of 5" nail would I use to compare costs? Common 5"?

[Redoverfarm]

Jumpinfrog I would have probably used plywood between the 2X material and glue.  The nails are commonly 16d. You do not have to get a nail the width of your beam. You nail two 2X together and then add the third and nail it to the other two.  On the screws vs nail I don't believe you will get the "shear" strength with screws as compared to nails but that is just MO.  I'm sure Pegg will drop in and let you know.

[ScottA]

I never use screws in structural applications they can break where a nail will bend. I'd check the screws by trying to bend one first. If it snaps I wouldn't use them. I used #20 common nails to put my beams together nailed from both sides. If the screws will bend then I'd say you'll be ok with them. John Raabe knows best I'm sure but every 6" seems like overkill to me.

[glenn kangiser]

What Scott said -- the screws are  not allowed in inspected code stuff  around here due to the shear/break thing.

While they probably will hold as John said, the nails and glue is hard to beat time wise - cost wise and making things work together properly.

I used screws in a large door to hold giant hinges on and about 1/2 of them sheared in the first year due to wood shrinkage.

[John Raabe]

It is very true about the brittleness of screws. I overdid the placement of the screws to raise the shear threshold higher than would likely be needed.

PS - NICE DOOR Glenn. Bet it does weigh a few pounds.

[glenn kangiser]

Started out around 400 or so when wet (guessing as it took 3 of us to stand the door and frame when putting it in) but I think it's a lot less now.  Maybe 200-300

[dogneck]

Glue-   I was told that you need a special glue to do the beams. It is resoncor or something like that.  It sets and does not permit any movement.  Typical construction adhesive will move and not work.>?
Any comments, as I will be making a 6x12  x 24 ft beam soon.

[Redoverfarm]

dogneck you might check out Titebonds Polyurethane construction adhesive.  Not real sure what the composition is but it is recommended where regular construction adhesives is not.  Maybe there website might have something.  I am sure that everyone else just uses regular but you may have a point.  I know that they have a tech support @

Technical Support
Phone (800)347-4583
Fax (614)445-1295
e-mail Technical Support

Also you might try

http://www.thistothat.com/

[John_C]

Here is one supplier for resorcinol glue

http://www.castlewholesalers.com/DAP-WELDWOOD-00227-Waterproof-Resorcinol-Glue-Pt-.html

And a tech pamphlet

http://www.dap.com/docs/tech/00030205.pdf

It is a waterproof 2 part glue.  A brown powder that you mix with a purple liquid.  A true waterproof glue that will withstand prolonged immersion and ,so they say, boiling.  It is very strong but unlike most epoxies  is not gap filling.  The glue joints have to fit very well.   Pricey stuff too.  PEG may know of more modern alternatives.