buildup bem question

[beckhamk]

i wanted to ask a question that just hit me, when doing a buildup beam I am assumming that this is normally using DF#2 or better 2x12's correct?  Why wouldnt you use pressure treated for this or do you?  From seeing all of the picks of people building on the forum it doesnt appear that anyone is using the pressure treated for these beams.

[Redoverfarm]

Normally PT is used for ground/or near ground contact where the wood would be exposed to water or moisture to resist rot and insect penetration. If your beams are going to be in the dry above the ground then white wood will work.  I would however use a PT foundation plate if you are going to build up a block foundation/crawl space. Hope this answered your question.

[Don_P]

There is nothing wrong with using treated there. The pics of exposed girder ends in whitewood make me cringe. Treated here is also often a stronger species/grade of material. A downside is that treated comes with higher corrosion problems so everything that touches it needs to be ACQ rated. Treated is usually very high moisture content, plan on shrinkage.

[Redoverfarm]

There is nothing wrong with using treated there. The pics of exposed girder ends in whitewood make me cringe. Treated here is also often a stronger species/grade of material. A downside is that treated comes with higher corrosion problems so everything that touches it needs to be ACQ rated. Treated is usually very high moisture content, plan on shrinkage.

Don unless they are exposed to the elements I personally wouldn't see a great problem.  They could always be sealed or treated which should take care of any problems.  In fact unless you bought a deep penetration PT (below ground) the treatment would be minimal and hardly any if they had to be end cut to work out the demensions.

[beckhamk]

let me through in some more info.... I plan to use a build is beam (girder) down the center of our floor.  This girder will sit in a pocket on each end with block piers down the center of the length of the cabin. The foundation is a block crawl.

So which route would you guys go.  I'm assumming you both of your opinions will be the same?

[Squirl]

It depends.  Untreated wood should not be in direct contact with concrete.  

[Don_P]

It changes my stance. As Squirl pointed out you need to isolate untreated from concrete but the beam is protected from the weather. I've never used treated in that situation except in the bottom of the beam pocket. Remember to leave 1/2" airspace around the beam in the pocket.

[Erin]

It depends.  Untreated wood should not be in direct contact with concrete.  

And that's true. 
But IMO, sill seal or even a couple of asphalt shingles can keep the beam from contacting the concrete and it would be an awful lot cheaper than PT lumber. 

[Squirl]

IIRC, most construction books I have seen call for a piece of PT wood on the sill or in the pocket to prevent direct contact.  This way the beam has something to nail to and the pt wood can be fastened to the foundation through sill or J. bolts.  In practice I have seen this accomplished through many means including metal flashing.

[davidj]

If you're worried about the contact with concrete at the beam ends, there are Simpson hangers that hang over concrete blocks.  They cost real money but save time cutting the block.  I use these with my LVLs that do the same jobs as your 2x12s.  We use our crawl space for food and drink storage (aka "the wine cellar") and it's nice not having a large area of exposed PT wood in the middle of it.  The PT sill plates are less of an issue as they're pretty much inaccessible.

[John Raabe]

Here's a typical detail for girder bearing in a foundation pocket. You normally size the pocket to provide 1/2" Min airspace around the three sides of the beam not bearing on the PT wood or moisture stop at the concrete bearing surface.

[beckhamk]

I have a few questions about this.... John commented above saying "not bearing on the PT wood"  but the picture says you would have a 2x treated bearing block?  So should you or shouldnt you use the PT there.


Here is another question , trying to determine how best to handle the build up girding being flush with the sill plate.  We are doing a crawl foundation and have block columns running down the center of the cabin.  there are two girder pockets. Our contractor made the pockets a little bit taller. Meaning that if I place a 2x12 in the pocket I am 2.25in short.  So we are looking at running a 2x6 on the top of the girder like you would on an I-beam.  That leave .75, which i was planning to use 1x6 or 1x8 on the bottom of the girder which would sit in the girder pocket and on the tops of the columns.    So my question is it ok to put the 1x6 or 1x8 under the girder or should i put that somewhere else or use steel plate shims ?

I will be assembling this onsite, an tips for putting this together onsite for the easiest and safest way? 

Lastly on leveling the sill should we worry about that as we are building the buildup beam or wait till the beam is built and in the pockets then use a bottem jack to raise it and insert shims as needed?

Thanks,
Kyle

[MountainDon]

I have a few questions about this.... John commented above saying "not bearing on the PT wood"  but the picture says you would have a 2x treated bearing block?  So should you or shouldnt you use the PT there.

You need to include more of that sentence of John's in order to make sense of that.

"1/2" Min airspace around the three sides of the beam not bearing on the PT wood "

That is a min. 1/2" air space between all concrete to wood beam interfaces. (1) The end of the beam to concrete, and (2 & 3) each side face of the beam to concrete. A PT block can be placed on the concrete as illustrated. And the non treated beam can then sit on that PT block.

[Don_P]

You can put a 2x on top of the girder to build it up and a treated or steel shim is fine under the girder. If you use steel I prefer to put a piece of tarpaper or something between it and untreated wood as the steel will occassionally sweat. The minimum bearing length of the girder on concrete, into the pocket, is 3" but more is preferrable. Don't forget the airspace behind and beside the girder inside the pocket.

For assembly build it up in place 1 stick at a time, don't try to assemble the whole thing and move it to the pocket, it'll get heavier and floppier than you would ever imagine trying to muscle it around. All end joints need to occur over a pier with at least 3" of length of any piece bearing on the piers. There needs to be treated or some moisture break on top of the pier under an untreated girder. You should be able to pull a string across the top of the sills and build the girder to correct height as you go but if you fail a jack and shims will work. At that point shim is thin steel plates or hardwood, preferrably steel plate. Pine or cedar will probably crush under load, you want nice big full support under the girder rather than small crushable spots of support. A power planer is nice to have handy if the mason missed his elevations anywhere, which is quite common. I've also tuned the top of the build up with a power planer to get everything nice and flat. Taking a bit of time to start square and level will make life a whole lot better through the rest of the build.

[beckhamk]

DonP - when you made this statement " All end joints need to occur over a pier with at least 3" of length of any piece bearing on the piers."  did you mean 3" into the pockets or did you really mean that the joints of the build up beam need to always be on a pier? 

We have concrete block piers spaced out down the length of the cabin, I was looking at johns build up beam diagram here:  http://www.countryplans.com/builtupbeam.html and the joints offset for each row of 2x12's.  So I wasnt sure if we should not be offsetting them now or what?

thanks,
kyle

[Don_P]

The joints always need to occur over a pier by code and in general unless you have an engineer's layout. There is room for discussion there, the joints can occur at the inflection point of a beam over multiple supports but that was muffed in the field enough that the codebook basically said "keep it simple, make the joints over the piers". If you place the piers less than 8' apart there is the opportunity to stagger the joints between plies.

[beckhamk]

Don - With regards to these build up beams and the joints and piers.  I assume that as long as we are using the correct 2x size for the span, that you can use whatever length you wanted to for the build up beam?  IE:  say your piers are 10ft oc apart, instead of having to use 2x 20 footers, we could use 10 footers correct?

[Native_NM]

As long as the connection is over the pier, correct.  if the math works out, try to stagger the connections,  especially if it is triple, to add strength. 

[beckhamk]

I would like to thank everyone for their input on the build up beam!   Its done and completed. wow that was pain more so because we starting in the rain and had to wait for that to stop and then it was really hot and humid arrggg... Don-P - wow you werent kidding when you said those beams get floppy. I was really surprised to see how floppy they are when putting them up. But once completed and top place on not bad.


thanks again!

[MountainDon]

I was really surprised to see how floppy they are when putting them up.

I should have said to build them in place. Then only one 2x is handled at a time and the finished beam does not need to be moved.