# Patio Beam Question



## misbhavn (Nov 19, 2010)

I have a question for the experts. I am going to build a 14x16 patio cover on the back of the house. This will be tied into the main structure. It will extend 14' from the house abd will span 16' across. For the 16' beam, I plan to sandwich a piece of 1/2" plywood between two 2x12's. I plan to use joist hangers on the header where I tie the beams into the back of the house. The problem is I can't find a joist hanger that will accommodate two 2x12's with plywood sandwiched in between, unless I order it online. I can find one that will take just two 2 by's.

My question is this, how much load capacity am I giving up if I just use two 2x12's without the plywood sandwiched between? This is on the 14' span, not the 16'. Keep in mind this will be holding up a roof. I don't want it to sag later either.

Here is a pic of one of the spots where I will be tying into the main header.








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## GT11 (Jan 1, 2013)

I am not exactly sure I understand which beam you are talking about but that isn't a long span. Are you talking about the beams that frame the patio, then you will hang joist in between them? I have double 2x12's spaning 16' on my dock without a problem and the joist are single 2x8's.


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## misbhavn (Nov 19, 2010)

I was afraid I didn't explain it very well. This pic is the main header that runs the length of the back of my house. You can see a window and my back door that goes out to the patio.

From this header I plan to mount a joist hanger which will support a beam which will be one side of my patio cover. I will do the same thing 16' down which will be the other side of the patio cover. These will be 14' long and mount to a post at each corner of the patio. Then, a 16' beam will span along the outside of the patio to each of the posts.

Again, the 16" beam will be two 2x12's with a 1/2" pc of plywood sandwiched between. I'm wondering if I can just use two 2x12's on the 14' span and forego the plywood between them. My concern is that it has to support the weight of the roof.


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## the hook (Aug 8, 2011)

IMO, and I've only framed about 6 or 700 houses, the plywood, FOR THE MOST PART, is "just a spacer" to get to 3.5 inches...I have done solid ply headers and sure, it adds a little strength, but not that much...Just get a good exterior glue and then nail or screw the 2X12's good...

I'm surprised you can't find hangers for 3.5" though...You could go with a Micro-Lam/Paralam and they are either 1.75 or 3.5 and I use hangers all the time for them...I also use 3.5" wide floor trusses that have hangers. Check if you have a truss co in the area...


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## misbhavn (Nov 19, 2010)

the hook said:


> IMO, and I've only framed about 6 or 700 houses, the plywood, FOR THE MOST PART, is "just a spacer" to get to 3.5 inches...I have done solid ply headers and sure, it adds a little strength, but not that much...Just get a good exterior glue and then nail or screw the 2X12's good...
> 
> I'm surprised you can't find hangers for 3.5" though...You could go with a Micro-Lam/Paralam and they are either 1.75 or 3.5 and I use hangers all the time for them...I also use 3.5" wide floor trusses that have hangers. Check if you have a truss co in the area...


Appreciate the input. I can find the hanger in 3.5", but I will have to order them. I have only looked at the box stores (Home Depot, Lowes, etc).

Should I just leave out the plywood on the 16' beam as well? Will it make any difference? I piocked up some liquid nail to use between the 2 by's. Will that work or should I use something else?

Again, thanks for the input.


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## misbhavn (Nov 19, 2010)

I was able to find the hangers I needed locally so I opted for the 2X12's with 1/2 plywood in between. I'm beginning the construction of the patio this weekend and will be installing the ceiling joists...which brings a new question...

I plan to use 2x6's for the ceiling joists spaced every 16". All it will hold is the ceiling material. There will be no storage above. Will 2X6's @16" be enough?


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## yakPIRATE (Jun 23, 2012)

2x12 with no plywood is more than enough.


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## misbhavn (Nov 19, 2010)

On the ceiling joists...I forgot to mention that the span will be 14'.


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## RB II (Feb 26, 2009)

Use #1 material. 2 each 2x12s will be fine. IIRC, the code allows #1 2x12 to span 16' as a ceiling joist.


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## the hook (Aug 8, 2011)

OK, I just saw this...I just happened to wonder where you are putting the hangers for the 16' bm? On the end of the 14'?? 

Yes, 14' 2X6 should be fine, imo...With minimum sheathing or ceiling tile, it should be fine...You could run a row of blocking in the center or a strongback to help...


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## misbhavn (Nov 19, 2010)

the hook said:


> OK, I just saw this...I just happened to wonder where you are putting the hangers for the 16' bm? On the end of the 14'??
> 
> Yes, 14' 2X6 should be fine, imo...With minimum sheathing or ceiling tile, it should be fine...You could run a row of blocking in the center or a strongback to help...


The hangers are going on the top plate of the back wall. The caover will be 14x16. Here is a pic of the back of the house when I was having the new slab poured. I will have two beams extending out 14'. The first beam will be just above and to the left of the back door. The other will be 16' to the right...a few feet to the right of the 3 windows. You can see where I dug a footer for the post in the pic.

The ceiling joists will run perpendicular to the house along the 14' span. All it will be supporting is the ceiling sheathing and a ceiling fan.

I had to google what a strongback was, but I like the idea. Does a strongback have to be one continuous piece of lumber or can it be in two pieces?








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## GT11 (Jan 1, 2013)

It is better if it is made from one piece but not necessary. If you are making a "T" or "U" shaped strong back, just stagger the joints.

I think you are fine with the double 2x12. I usually don't sandwich anything in between them for that span. The lateral bracing as suggested above will give you extra strength also. On really long spans, I have sandwiched a 4"x1/4" steel plate between 2x12's but that was a very long span. You also are not supporting a lot of wieght. My boathouse has a 16' span which is a double 2x12 around the edge and 2 x 8 joist hung on the 2/12's.


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## Gottagofishin (Dec 17, 2005)

Agree with the above, but I would support it in the middle with a post. I will bow over time without that support. Think about how many 10 year old garage doors with wood headers you've seen with just a slight bow in the middle. 

If you don't want a support post in the middle, then use an LVL beam. It won't sag over time.


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## the hook (Aug 8, 2011)

Not sure a strongback will work, BUT it depends on your joist placement...I guess you will keep the top of the beam even with the top plate on the wall?? Then the joists will sit on top plate/top beam? If not, then you would need a back nailer on the wall, and hangers for the 2X6 and flush with the bottom of beam?? With the joist on top, they will be 5.5 inches above...THEN, the strongback will add ANOTHER 5.5 inches ABOVE, which means the bottom of your rafter would have to pass OVER the SB(strongback) in effect you would need a steep roof to clear, and it appears you have shallow...Your rafter/joist should set next to each other...If shallow, they should also "overlap" for a considerable distance....You can nail these together...I will look for some "sketches" or prints to explain...


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## misbhavn (Nov 19, 2010)

the hook said:


> Not sure a strongback will work, BUT it depends on your joist placement...I guess you will keep the top of the beam even with the top plate on the wall?? Then the joists will sit on top plate/top beam? If not, then you would need a back nailer on the wall, and hangers for the 2X6 and flush with the bottom of beam?? With the joist on top, they will be 5.5 inches above...THEN, the strongback will add ANOTHER 5.5 inches ABOVE, which means the bottom of your rafter would have to pass OVER the SB(strongback) in effect you would need a steep roof to clear, and it appears you have shallow...Your rafter/joist should set next to each other...If shallow, they should also "overlap" for a considerable distance....You can nail these together...I will look for some "sketches" or prints to explain...


To answer your questions, the top of the beam is even with the top plate of the back wall. My plan is to have the top of the joists even with this as well, leaving the bottom 5" of the beam exposed. Then the strong back would run from the top of the beams across the joists. Initially I was thinking I would run the joists along the 14' span, but this would put them perpendicular to the rafters. Would this be acceptable if I use collar ties? After thinking about it more, I'm wondering if I shouldn't run them parallel to the rafters across the 16' span.

I got the beams and posts up this weekend. I plan to start another thread to chronicle the progress as I go.


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## misbhavn (Nov 19, 2010)

Can anyone tell me how to calculate the length of my ridge board? I want to make sure I get two boards long enough so that I only have one splice in the ridge board.

I have a gable roof extending out perpendicular from the existing hip roof. Top plates are the same and I plan to match the overhang to the existing structure, if that makes a difference. Existing structure has a 5/12 pitch and I will be matching that as well.


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## the hook (Aug 8, 2011)

Yes...By looking at your roof, the rear(new) roof is 16' wide(?) and 14' out from existing wall?? The new ridge would still only be 14', cut on a reverse 5/12 pitch to lay on the existing pitch...The new ridge would start in from the new beam at 8'(half span/width)...Then it will set on the existing at 8' in from existing wall of your house....Having a hard time on my end with trying to make a drawing or copy pics??? I'm not too comp literate...Will try though


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## misbhavn (Nov 19, 2010)

the hook said:


> Yes...By looking at your roof, the rear(new) roof is 16' wide(?) and 14' out from existing wall?? The new ridge would still only be 14', cut on a reverse 5/12 pitch to lay on the existing pitch...The new ridge would start in from the new beam at 8'(half span/width)...Then it will set on the existing at 8' in from existing wall of your house....Having a hard time on my end with trying to make a drawing or copy pics??? I'm not too comp literate...Will try though


I don't know if it matters, but it's actually 16' across from the outside of one beam to the other, with a 21.5" overhang. This should give me a roof width of 19' 7". I don't think any of this would affect the length of the ridge board though.

The patio extends out 14' 6" from the back wall. This will be where my ridge board ends.


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## misbhavn (Nov 19, 2010)

After reading your post again, it sounds like you are thinking the addition will be a hip roof.


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## the hook (Aug 8, 2011)

OK, overhang has O to do with ridge, just rafter lengths....So, I edited my post with a half-*** pic...It should give you an idea?? The ridge is the exact same as the new section, I guess 14'6 by your last post?? If you make a gable, then 14'6 plus 8', if both roofs are same pitch...A drawing/print sketch would help...Here is a roof I of a house I framed a few years back...There are "about" 350 sheets of plywood on this...


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## misbhavn (Nov 19, 2010)

Okay, that makes sense. So two 2x8x12's will get me there with one splice. That's the info I needed. Thanks for the input.

I will get some pics posted of my progress in the next few days. So far, I have cut the overhang back on the existing roof, the beams are up and I have the ceiling joists in. I decided to run the ceiling joists across the 16' span. It just made more sense to me do it that way so that it would keep the beams from bowing out from the downward pressure from the rafters. I don't know if it really mattered or not, but I'd rather be safe than sorry.


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## the hook (Aug 8, 2011)

OK, how's this?


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## misbhavn (Nov 19, 2010)

Now, I've run into another issue. The width of the patio from outside of beam to outside of beam is 16'. Half of that is 8' so the top of my ridge board should be 40" on a 5/12 pitch, measured from the top plate, correct?

I'm doing this alone so I had to get creative to find a way to hold my ridge board up. When I cut my first rafter, I used the step off method. From the plumb line of my birds mouth, I stepped off 8 times, then subtracted 3/4" for half of my ridge board. For whatever reason, my rafter is about 4" higher than the ridge board.

From the plumb line of the birds mouth to the plunb line of the ridge cut is 103 1/2".

Does this sound right? what am I missing?


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## misbhavn (Nov 19, 2010)

I ended up just raising the ridge board to line up with the rafters. I still don't get the math of it though. Common sense tells me a 5/12 pitch rises 5" for every foot. 1/2 the width is 8' (8x5=40).

As far as I can tell, I measured everything correctly. According to my framing square, a 5/12 pitch will run 13" for every foot of rise, so 8x13=104". Take half the width of the ridge board and that would be 103 1/4", which means I was off on my original measurement by 1/4". If someone could explain where I may have gone wrong, I would appreciate it.

The valley rafters should be real fun.


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## the hook (Aug 8, 2011)

This tells me you have a 4" heel height...It is 4" to the top of the rafter off of the beam on your plumb line....That is correct...You did fine...Yes, I've done WAY to many roofs by myself, and you learn tricks....As said, layout with sq, and you will get your run/ht...It is a learning game for you...I'm sitting here thinking of a dozen ways to do it, but for you, not knowing exactly what I mean, it's hard...btw, if you "layed out" the rafter with a sq, instead of the 13 X 8 = 104, and were a little long, that is normal...It seems that for whatever reason, you will ALWAYS gain with a fr sq, never lose length...If you do not have or use a speed sq, use 5/17 for the pitch of your valley, cut to a 45* bevel in center of board...FWIW, I always just measure each valley, as opposed to "booking" it...A half inch here or there will never be seen...Thing with the val is to have a common on each side, so you can accurately get the length from top at ridge to the bottom, which is at the top of the heel cut where the commons meet...Look at some sketches and it will be easy to understand...you seem like you know what your doing...Once you have the length of val, it will be cut 1) long point 5/17 'pitch' ,double 45*bevel at the top(ridge) to short point 5/17 'pitch', double 45* bevel...."THEN", you measure 'down' the point created by the bevel cut, 4"(heel hgt) and it will be a reverse 5/17, or a sq cut to the 'pitch"....That should really confuse you now! My job is done !!


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## misbhavn (Nov 19, 2010)

It never occurred to me that the heel height was raising to total height of the ridge board. It makes perfect sense.

For the valley, I was planning to pop a line from the tip of the ridge board where it meets the existing roof down to the point where the sub fascia boards would intersect, then put in a nailer along that line.

Seems like from there I couold just measure from the top of the ridge board to the outside of the nailer and get that distance. The ridge cut would be just like my common rafters (using 5 and 12 on my framing square), right? Then on my valley cut, I would cut at 45Â° (horizontal) and at a 23Â° bevel. Would that work?


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## the hook (Aug 8, 2011)

OOps....OK, I was thinking a normal valley....OK, you could clear your shingles back enough to pop a line even with the edge of ridge where it meets existing roof to top of sub facia(2X8?) where they meet, or the edge of overhang etc...If you are off a "little" it won't really show...As in little, I mean 1/2 inch or so, nor "inches"...Now, that line is good if just cutting rafters to "it"....If you put a "nailer" on that line, it will be "above" the roof line, because the chalkline is at zero ht, where the nailer will be 1.5"(?)...I would just cut rafters to the chalkline....5/12 pitch(23*) on top but a reverse 23, or 67*"on the square", then a 23* bevel to sit on existing roof...The 2 "pitch" cuts will always total 90* if square to each other...The reason I say that you "can" cut to the chalkline is you have no roof load, such as snow etc....between the rafters, the ply will just set on ply..."IF" you go with the nailer, you will have to allow for the height above the ply to match pitch...Really simple, if you already know...With a nailer, you may have to double as far as width, because the rafter(2X6?) cut on a 67* is a Loooong pitch cut, and from your long point, which would meet the edge of your "laydown valley" (what we call them), there would/will not be a lot of bearing....Again, I will try to send a pic, but I'm having trouble from sketch to post?? Says no good file??


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## the hook (Aug 8, 2011)

OK, here...This is NOT really the right pitch, so it is not a good "picture"...I probably have about 30*/60* here...I am not good on this machine...I had to get a picture that would post, then ERASE the whole thing...lol...By reading your reply, your 23* on the bottom "is" 67*(which is the long side of the framing sq when set at 5/12, also called "level cut" Top is "plumb cut") and the bevel is 23*, which is the angle needed to set on your existing roof...


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## misbhavn (Nov 19, 2010)

Thanks for all the information hook. I completed all of the rafters on Friday. I did a little research before I started on the valley rafters and figured out how to do it. It's not as good as a journeyman could have done it, but I thought it turned out pretty good for my first time to frame a roof. I got up Saturday morning and naile up all of the full sheets of OSB on the roof. Now I need to get all of the edges cut in and shingled. I hope it doesn't rain this week.  Will the OSB be ruined if it gets rained on a couple of times?

On a side note, How would you suggest I attach the valley nailer to the existing roof? I used 3" deck screws, but I'm not sure I trust it. If I need to do something else, I need to get it done before it's coverd with OSB.


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## the hook (Aug 8, 2011)

Not sure what exactly you mean by "valley nailer"....If sheathed, your nailer is covered already by osb? I would felt the roof as soon as possible, unless no rain....It should only take a few min, maybe half hour or so to cover with a slap stapler...I'm not sure how you did the laydown valley, so...If you removed shingles, then rain will get in your house...If not removed, and you just went over the shingles, then just the new will get damaged...Yes, it will at least swell the joints on the sheets, if they get wet..I'm not talking a passing shower, but a good rain will swell the edges and you will see it...Had it happen, but it was the builders fault...


OK, I just reread your post and see that you do not have the angle cut pieces in....I guess, without seeing, that the screws are plenty...If in the rafters below, I'm sure...You do have some bad winds though...Just make sure its screwed as good as possible..


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## G-Money (Aug 3, 2007)

I sandwich heavy gage sheetmetal between any structural 2x12 or 2x10 header. Remember to use a nail/screw grid pattern of three nails every 12".


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