First time poster long time DIY'er, 2

[KatyTX]

First time poster long time DIY'er, fellow engineer (IT Networking) looking for help.

Looking for advice on a covered patio build. It will attach to the detached garage that has a hip roof on it. I will add a ridge and carry the backside of the roof pitch all the way out over the new patio addition (add another hip roof basically. The patio is 22 feet long and will have (3) 8x8 cedar post. The post are 15 feet off the garage wall and about 11 ft apart. I am trying to determine the size of the beams I need. I will likely use multiple ply of 2x12 like a 4plyx2x12 for all my beams but I want know what if that is to much. I really want to get down to 2ply 2x10 cedar IF possible.

I have three 15 foot spans (post to garage). On Garage side I will sit on trimmer/jack studs under the garage sill plate. I am not planning on using a ledger board. What size beam for this?

Then I have the 22 foot span with a post in the middle. So I guess 2x 11ft spans. Again I was thinking 4plyx2x12 but want to use 2ply2x10 cedar again . Whats the recommended size beam here?

There will be a ridge 2x6 with 2x6 rafters and a composite shingle roof. I will also run some 2x6 joist for a cedar t&g ceiling between the beams. 12/8 pitch on the roof and I am in Texas where we do not get snow but have gotten some hurricane winds in the past.

I would love for the beams to be 2x10 instead of 2x12 if possible because it allows me to use cedar planks readily available at my Home Depot. Is this possible? Attached are some pictures to give an idea but the roof is drawn wrong. The new ridge will be as high as the existing and the back existing roof will be the same all the way across with no valley. Only one side will have a valley.

I'm sure you guys get these kinds of questions all the time, Im sorry but really appreciate any input.

 

[phamENG]

Sorry, KatyTX. For most of us, what you're asking us to do is...our job. You're asking us to analyze this structure and select appropriate beam sizes. That's what most of us get paid to do - so I hope you can understand that most here are not in the habit of providing such designs for free.

That said, you look like you have a clue. Take a look at the International Residential Code (or Texas Residential Code - several states rename it and add some custom modifications). Under wall construction, there is a table for header sizes based on width of building, snow load/roof live load, and span. You can use that to help you select your beams. Not sure if they have values for cedar, but would be worth a look. Once you put it together, you can submit to your building official for review and approval for permit.

If you don't feel comfortable doing that, I'd suggest you contact a local architect or structural engineer for assistance.

Good luck.

 

[KatyTX]

Thanks for the reply phamENG. I actually live outside of city limits where permits are not required. I took about 12 semesters of architecture in HS back in the early 90's but ended up supporting the network for the worlds largest engineering and construction company. But unfortunately after 20 years working there IT and Engineers don't talk to each other much so I don't have any contacts to run my question by. :-( I've looked at several sites where spans are discussed which is where I came up with the 4plyx2x12 but I was just looking for a little reassurance and was hoping someone could provide a 2x10 solution. Some of the sites had free calculators but none seemed to fit a patio scenario. Anyway I see your post already got a like and I am the outsider here I'm sorry I was not sure what to expect but thanks for letting me know.

 

[rb1957]

Texas you say … they get tornados there, don`t they ?

I understand trying to do this on the cheap, but I think you should pay someone for the plans. Maybe talk to a home reno outfit ? online ??

I understand wanting to use 2x10 … if sized for 4x 2x12, then maybe 6x 2x10 ??

another day in paradise, or is paradise one day closer ?

 

[SwinnyGG]

Thanks for the reply phamENG. I actually live outside of city limits where permits are not required. I took about 12 semesters of architecture in HS back in the early 90's but ended up supporting the network for the worlds largest engineering and construction company. But unfortunately after 20 years working there IT and Engineers don't talk to each other much so I don't have any contacts to run my question by. sad I've looked at several sites where spans are discussed which is where I came up with the 4plyx2x12 but I was just looking for a little reassurance and was hoping someone could provide a 2x10 solution. Some of the sites had free calculators but none seemed to fit a patio scenario. Anyway I see your post already got a like and I am the outsider here I'm sorry I was not sure what to expect but thanks for letting me know.

Careful- just because you're not in an incorporated city doesn't mean you can just do whatever you want without a permit. I know 100% that if you live in Harris county, this qualifies as an addition and requires a permit from Harris County. I can't speak for Ft. Bend or Waller counties, but you should check before you do anything beyond drawings, and you should be prepared to defend your unpermitted structure should someone challenge you.

With that said - if it turns out that what you're doing does not, in fact, require a permit, the code will still provide direction. Just because it won't be permitted and inspected doesn't stop you from using the code to verify that your design meets the same requirements a permitted addition would require. When reviewing the code, remember that what is shown is not exactly how a building should be built; it's the minimum standard. Design strength of your structure can exceed the code if you want it to, or if it makes you more comfortable, or whatever.

Just so we're clear, you should definitely check and make sure your county doesn't require a permit (this is unlikely in my opinion) and you should engage a structural engineer as well. It will cost you much, much less to have this designed for you than it will down the road if you have an issue.

 

[STrctPono]

A couple notes, you keep referring to a 22ft span but your sketch shows a 27ft transverse span. Not sure where the 22ft comes from. You mention a ridge 2x6 with rafters. Is this a ridgeboard? Are your 2x6 joists going to be detailed and function as rafter ties? Otherwise, your perimeter beams will need to resist the spreading force of your rafters. Or you can change that ridgeboard to a ridgebeam. How are you going to resist the lateral load parallel to your (3) 8x8 posts? Currently, that is going to be flopping in the wind. In my area, we would pour an isolated concrete footing (NOT how you have it currently shown where it is supported off the edge of the thickened slab), place 12" or 16 square CMU block columns all the way up to the beams. Fasten the beams to the masonry columns with some Simpson embed column caps and your CMU provides the stiffness and resists the lateral load. You can always put veneer over the CMU to make it look nicer. I also don't like the way that you are proposing to tie back to the existing structure. You are going to be dumping a ton of load into the structure and foundation without having any real idea whether or not it can handle it. Cedar looks nice but is weaker than douglas fir. It works well for outdoor pavilions and pergolas since its decay resistant and you don't need to incise it. If you were to try and do the same thing with Doug Fir you would need to incise it which would automatically make it look horrible and no one would want it. Using T&G cedar for the ceiling is logical since it looks nice but doesn't make much sense for the beams since it's weaker and super expensive. I can touch more on this topic if you want but it involves treatment options and what is appropriate for your application and what is available in your area.

Let's assume your two outer beams support the roof loads and you take care of your spreading forces with rafter ties. Roof framing, plywood, asphalt shingles, roll paper, and cedar T&G ceiling weigh 19 psf. No snow loads considered. 20 psf Roof Live Load. Not considering Wind Loads (which is a considerable factor since you mentioned past hurricanes). Assuming dry conditions with temperature 100 - 120 degrees F.... A 6x18 Douglas Fir Beam would barely make it. Not a chance that 4 nested 2x12 cedar members would work. Your more likely scenario is to be using something like a 5.5 x 15 Glulam Beam. Or you could probably go with a 5.125" architectural grade glulam if looks is a big concern.

As you can see, these are pretty large members and is going to put a serious damper on your plan to just nest 2x members together. I am an avid (and I stress avid) DIY'er. I've personally built spiral staircases, outdoor redwood pavilions, decks, fences, reroofed my home, remodeled my entire house.... but this project is a pretty massive undertaking unless you know what you are doing. I know that you want to nest the 2x's because it's easier to handle but now that this plan won't work, just imagine trying to handle a 15ft long 5.5 x 15 beam. The size beams that I mentioned should probably make you realize that you could be at risk for seriously undersizing some members and having a disaster on your hands. I would definitely heed phamENG's advice and hire a local structural engineer who can economically size all of this for you. I definitely would not ignore the wind factor as this can get pretty significant.

 

[LittleInch]

You have some pretty major mods going on there.

Looks very similar to my house extension.

Don't forget you need to figure out how to extend the portion over the original roof / garage where the loads increase.

There looks to be a flat roof portion as well.

My design by the structural engineer used a steel beam from the midpoint out to the far wall of the extension and had a V shaped support out to the end of the flat roof section. You don't have walls to support the side so that 15 ft span is taking all the roof weight if you don't add some sort of middle span from your central post back to the main house.

He used cross ties to hold the roof together and stop it all spreading out.

Definitely needs someone who knows what they are doing here, regardless of permits. If / when you want to sell you'll need to provide some data about the design and a sketch won't do - people will want calculations.

Wind uplift is different as well.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KatyTX]

Thank you EVERYONE for the replies, I really appreciate it. I'm hearing you all say the same thing which is exactly what the professionals should be saying. I will have to rethink this.

 

[JLNJ]

It is important to find a simple, strong load path for your lateral forces to get to the ground.

Think about stability - not just how big the rafters need to be.

 

[jayrod12]

Think about stability

I tell this to all new engineers in the office. Figure out the lateral system for your structure as early as possible. The rest of the design is simple sizing of beams and columns. Finding places for shearwalls, bracing, moment frames etc. is always the biggest battle.