Flat roof carport help

[Afraz89]

Hello, I’m currently planning out a carport build for my home where there’s not much code enforcement at all and I’m trying to figure out what size beams will be adequate.

My main concern is the 18 foot span from post to post. I want the entrance to be completely open so an additional post in the center is out of the question. I’m hoping double 2x12s will do but am willing to triple them if I have to

Here’s the basic plan

6x6 posts 8 ft on center running 24ft down each side of carport. (4 posts per side)

Double 2x12x20? beam running horizontally across opening of carport and between each post 8 ft OC

2x6 purlins 2 ft on center running the length of the carport

1x3 furring strips atop 2x6s to which sheet metal will be fastened.

Slope will be low. No snow load here. I’m thinking 6-8 inches over the entire span.

Anyways, will a 2x12 doubled be enough for an 18 ft span in this application?

Thanks!

 

[Mark K]

Two reactions.

I did not know that this forum is a design service.

Please clarify why you believe the IEBC governs instead of the IBC?

 

[e hilton]

Two re-reactions.
I thin’ it’s a common and logical assumption for non-construction folks.
Where do you see reference to IEBC in hid post?

 

[bill1952]

snow load?

 

[Afraz89]

Two reactions.

I did not know that this forum is a design service.

Please clarify why you believe the IEBC governs instead of the IBC?

Interesting. My mistake. When searching google it pulls up questions asked on this forum that are similar to mine, which led me to create an account here thinking I could get advice. I get it now though. Should have looked more into what this forum was about

 

[ICE]

Try chat gpt. I bet that HAL thinks that a 4”X16” with knee braces will work.

 

[Afraz89]

snow load?

very minimal here. I’ve seen up to 2” of snow once or twice in 15 years

 

[Afraz89]

Try chat gpt. I bet that HAL thinks that a 4”X16” with knee braces will work.

Yea obviously over kill. What are you too cool to say what you think will work? Is that why you call yourself ICE?

 

[ICE]

Well then, allow me to apologize for not validating your decision to use a pair of 2"x12". By all means, go with what you know. In my defense, it's not often that I encounter a NFG replete with Dunning-Kruger effect.

 

[Afraz89]

Well then, allow me to apologize for not validating your decision to use a pair of 2"x12". By all means, go with what you know. In my defense, it's not often that I encounter a NFG replete with Dunning-Kruger effect.

Yea… I really haven’t encountered any complete geeks since grade school so I don’t know how to deal with you either but anyways thanks for the advice

 

[ICE]

thanks for the advice

My pleasure and welcome to the forum.

 

[wwhitney]

This table in the IRC says that Select Struct Southern Pine 2x12s at 24" o.c. can span 18' exactly while carrying 40 psf live load and 20 psf dead load, with a deflection limit of L/360.

Chapter 5: Floors, Residential Code of the Texas IHB | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

So if we halve the load to 20 psf live and 10 psf dead (as is typical for rafter tables), the member spacing could double to 48" o.c. That's equivalent to two members at 96" o.c., assuming the purlins can carry the load to the 2x12s. Thus if your ground snow load is 20 psf or less, and if the dead load does work out to 10 psf or less, the double 2x12s would work for Southern Pine Select Struct grade.

[Since rafters don't generally need an L/360 deflection limit, from the 50 psf snow load / 10 psf dead load L/240 table we can similarly infer that Douglas Fir Larch or Hem Fir would also work in Select Struct grade.]

As to the purlins, the rafter tables say that 2x6s will work in any species and grade for an 8' span if the loading is 20 psf live and 10 psf dead.

However, the framing specified doesn't include any sheet good for a roof diaphragm, so I'm unclear on what the IRC would require as far as a lateral force resisting system, for wind or earthquake loading.

Cheers, Wayne

 

[ICE]

This table in the IRC says that Select Struct Southern Pine 2x12s at 24" o.c. can span 18' exactly while carrying 40 psf live load and 20 psf dead load, with a deflection limit of L/360.

Chapter 5: Floors, Residential Code of the Texas IHB | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

So if we halve the load to 20 psf live and 10 psf dead (as is typical for rafter tables), the member spacing could double to 48" o.c. That's equivalent to two members at 96" o.c., assuming the purlins can carry the load to the 2x12s. Thus if your ground snow load is 20 psf or less, and if the dead load does work out to 10 psf or less, the double 2x12s would work for Southern Pine Select Struct grade.

[Since rafters don't generally need an L/360 deflection limit, from the 50 psf snow load / 10 psf dead load L/240 table we can similarly infer that Douglas Fir Larch or Hem Fir would also work in Select Struct grade.]

As to the purlins, the rafter tables say that 2x6s will work in any species and grade for an 8' span if the loading is 20 psf live and 10 psf dead.

However, the framing specified doesn't include any sheet good for a roof diaphragm, so I'm unclear on what the IRC would require as far as a lateral force resisting system, for wind or earthquake loading.

Cheers, Wayne

Mark K is gonna love to see this.

 

[Afraz89]

This table in the IRC says that Select Struct Southern Pine 2x12s at 24" o.c. can span 18' exactly while carrying 40 psf live load and 20 psf dead load, with a deflection limit of L/360.

Chapter 5: Floors, Residential Code of the Texas IHB | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

So if we halve the load to 20 psf live and 10 psf dead (as is typical for rafter tables), the member spacing could double to 48" o.c. That's equivalent to two members at 96" o.c., assuming the purlins can carry the load to the 2x12s. Thus if your ground snow load is 20 psf or less, and if the dead load does work out to 10 psf or less, the double 2x12s would work for Southern Pine Select Struct grade.

[Since rafters don't generally need an L/360 deflection limit, from the 50 psf snow load / 10 psf dead load L/240 table we can similarly infer that Douglas Fir Larch or Hem Fir would also work in Select Struct grade.]

As to the purlins, the rafter tables say that 2x6s will work in any species and grade for an 8' span if the loading is 20 psf live and 10 psf dead.

However, the framing specified doesn't include any sheet good for a roof diaphragm, so I'm unclear on what the IRC would require as far as a lateral force resisting system, for wind or earthquake loading.

Cheers, Wayne

Thank you Sir! You just helped me out a ton with something that’s been bugging me for awhile. That’s exactly the information I have been searching for

-Austin