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walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 2589
Experience:  Over 30 years of Structural Engineering experience.
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I am building a 20 x 20 concrete patio slab (3 1/2" thick

Customer Question

Hi,
I am building a 20 x 20 concrete patio slab (3 1/2" thick with rebar) and want to install a free standing patio cover thats 16 x 16 made up of four corner 4 x4 x 8'posts with four 4 x 6 x16 horizontal beams with 2 x 6 rafters and a 4 x 6 x 16 ridge beam.
Should the four metal simpson bases in the slab for the structure be 4x4 or 4x6?
Would four posts hold the weight of the structure, or do I need to add more 4 x 4 posts or go bigger like a 6 x6 or?
Is there anything else I have overlooked on this project?
Thanks.
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  walkereng replied 1 year ago.

I can help

Do you have any kind of sketch you could draw and share with me?

I want to make sure I fully understand your configuration.

Customer: replied 1 year ago.
I would like to build the frame work like the top photo with a gable roof like in the bottom picture rather than a hip roof. The sides of the gable would be open. There is no fireplace. I am trying to determine how many posts I would need and the size of the post and simpson brackets which would be set in the slab before the concrete is poured.
Customer: replied 1 year ago.
Also do you know what the minimum distance is that I can build this structure from my neighbors wall / property line?
For example, I hear that if you are building an addition to your house it has to be 5'5" away from the property line to be legal.
I do not know if this patio cover would fall under those guidelines or I can build it closer, say 4' away.
Also the distance away from the property line is that measured by the tail of the rafters or post of the structure?
Expert:  walkereng replied 1 year ago.

What city and state do you live in for possible snow load consideration?

Expert:  walkereng replied 1 year ago.

On the zoning question, this would not be considered a principle structure, it would be considered an accessory structure. Some Zoning Codes have different setback requirements for the two different types of structures. You will either have to see if the Zoning Code is online for the jurisdiction you are in, or you will need to call them and ask that question about the setback requirements. My advice would be to call them 1st. A phone call is free and you want to make sure you are not assuming something that is incorrect.

Expert:  walkereng replied 1 year ago.

Let me know about your city and state and I can help you on the rest of the question.

Customer: replied 1 year ago.
My city is North Hollywood CA
Zip code is 91601
No snow here!
Expert:  walkereng replied 1 year ago.

I’d like to point out that a Professional Engineer’s standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for planning purposes only (general sizing and budgeting) and is based on the information provided by you. All loading cases considered are for vertical loads only, no lateral analysis has been completed. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.

For your 16' span ridge beam, you could use the following:

4x12 or 6x10 Douglas Fir (#1 grade beam)

For your two 16' span side beams that your rafter tails rest on, you could use the following:

4x10 or 6x8 Douglas Fir (#1 grade beam)

For your two 16' span gable end beams that your post supporting your ridge beam rest on, you could use the following:

4x12 or 6x10 Douglas Fir (#1 grade beam)

To make your structure look symmetric, I would use four 6"x6" Douglas Fir posts

Expert:  walkereng replied 1 year ago.

And also use the 6x members for the various beams I sized above.

Expert:  walkereng replied 1 year ago.

You can use Simpson Strong Tie post bases, see below:

http://www.strongtie.com/products/categories/caps-bases.html?source=catlist

Expert:  walkereng replied 1 year ago.

You will need to have a local engineer detail your connections, determine foundation requirements and check the lateral stability of your structure.

If you feel you have received a satisfactory answer to your question, click the Rating button that is appropriate. Experts are credited for each appropriately Rated answer they provide. If you have additional questions, please let me know. Thanks

Expert:  walkereng replied 1 year ago.

Let me know if you have any more questions

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