homebuilders / construction guys lend me your ear

[Redrig]

Hello all ,

I dont have the energy to start a new forum over this topic and I know there are some serious brains on this forum anyways.

Long story short , I am replacing my deck on my house it is 10' x 18'. I am doing trex decking with the structure built of pre-treated lumber.

everything is going great but I am hung up on one place. The beam or girder.

I can not locate an 18' piece in 4x here locally and am planning on laminating it out of 2x8x12 boards to span that , I have 3 supports for the 18' run . everything out here is 16' , the several lumber yards I have called say that by the time anything over 16' gets out here to Utah that it badly warps. just gets too squirly to use one gents terms.

looking at building codes , it says to never make a splice that is not supported directly below which is understandable.

my question is simply this . Can I have 2 splices under the SAME support ? (9 feet one side , 9 feet the other with both pieces spliced over the middle support ) I can not find any info about this anywhere .

my dad is an underground engineer (mining) he is worried about this turning into a "W" with the high spots being over the supports.

any thoughts ?

Thanks in advance

 

[tpenfield]

I think 9' is too much of a span for the girder. . . and you would not have continuity of the girder at the middle column. If you go with a 4th column, then you can make a 6' span and splice accordingly. Not sure how many ply of 2x8's, but if you go with 3 2x8's (12 footers) it may be better than just 2 ply.

 

[aspeck]

I think Ted is spot on with his recommendation. That is the way I would do it, anyway.

 

[Scott Danforth]

I would be doing 2x10's and like Ted mentioned with the 4 posts, however I would laminate 3 of them together

if you use the minimum 40# per sq foot for a residential deck you would be fine with the 2x8's. however 85# per sq foot is what most should use (its what is used in commercial structures).

if you plan a hot tub, you need to be better than 105# /sqft.

however I use 150#/sq ft when I do my load calculations just because......there is no load like an overload.

 

[Redrig]

I was planning on using the original beam its 4 x 8 x 18 and still very straight , it just has a touch of rot right at both ends where the joists will lay , ididnt originally see that rot until I tore the deck down.

but yeah , I think that is the way to go there , adding a 4th support .

Its crazy how here in SLC I cant find a beam in 20ft, only 16 . Ive called probably 5 lumber yards .

 

[Redrig]

and Scott brings up a good point , would 2 x 10 's eliminate the need for a 4th post ?

I can certainly go grab some of those in 12's

 

[JASinIL2006]

Have you looked into exterior-rated engineered beams? You ought to be able to get those in whatever size you need if you're really committed to three supporting columns. Of course, adding another column or two would certainly allow a smaller beam (and lower cost).

 

[Redrig]

honestly I havent even heard of those. I will look into it, as I mentioned I was planning on using original beam, so this threw a monkey wrench into the plans.

I was planning on having joists up tonight , looks like that isnt going to happen. Sounds like I just need to research more or just plan on adding that 4th post

 

[tpenfield]

Something like this . . .

https://www.fp-supply.com/st-louis-t...red-beams.html


. . . we sold them when I worked at the lumber yard . . . :thumb:

 

[Redrig]

yeah, that is exactly what I need right now

 

[tpenfield]

Local lumber yard that supplies builders might have 20 footers in stock , , , might be about $20/foot.

 

[Scott Danforth]

you can get a 25' long aluminum 8" I-beam for about $400

 

[redneck joe]

when I added my sunroom, i went triple 16's over 20' in 10' lengths splices. 6 supports. that was for the center run the midway to rim joists over a 22' span I did doubles, same support count. No calculations I aint that smart but i know it is more stout than most anything built.

 

[tpenfield]

I happen to be replacing the decking on my deck this weekend . . . Of course it is not up in the air and I have a flush girder, since it is so close to the ground.
.

.
I built this 28 years ago and the framing looks fine. So it will be just the deck boards, of which I have 48 16 foot PVC ready to go.

 

[Redrig]

I was able to hunt down a laminate beam here locally thank goodness.
Its a 3.5 x 11 or something , its a beast , it was a 44 footer and luckily a lumberyard was willing to cut off 18 feet for me at a reasonable price . Thank for the tip on those , I always assumed you just laminate your own beam on projects like this .

I will throw up some pics soon , I have all the joists on except the ends (doubles) and I cant find the dang concelaed hangers any closer than a 45 minute drive.

20 foot high end trex is going on it , hopefully tomorrow.

New forum looks good btw.

 

[JASinIL2006]

Sweet! Can’t wait to see it!

 

[foodfisher]

When I did trex, 12 inch on center joists was recommended/required. Sagging could result at 16 inch.

 

[tpenfield]

The 2020 Trex installation guide indicates 16" OC joists for 100 psf loading. 12" OC for 200 psf or if you are running the decking at a 45˚ angle to the joists.

 

[redneck joe]

when in doubt, go 12". unless deck is absurdly huge the cost isn't much more especially if spending the $ on trex.

My small deck is 7.5' run and I have 12's on 12"oc.

 

[Redrig]

yeah , I was worried about sagging , I amd using the trex "transend" line which doesnt have that ribbed or grooved portion out of the underside , the profile is solid to add strength . I did 16' OC as that is what they recommended.

I could use some additional help and thoughts , I am just about wrapped up with the decking surface (adding blocking between joists above the beam right now ) should be wrapped up with deck surface tonight. once blocking is in , 4 deck boards and shes done there.

so my next project is stringers and planning those out. Here is where I am running into confusion though.

What to do with the first step OFF the deck ? Is that level with the deck surface ? or 1 riser down ? I have seen it done both ways , and am unsure of which direction to go

I have double joists 2x8s on each end of the porch for added strength if that matters

thanks again all ,