Equipment Shelter Construction Questions

[rather]

I am going to build a shelter for some of my equipment This is a freestanding structure that is going to back up to my RV building. I have a few questions about beam sizing, rafter span and footing size. I live in an are that sees one or two snowfalls a year usually 6-8 inches max and usually melting in a week. I will not be getting a permit to do this work. I have a couple of illustrations below.

Questions

• Rafters- The rafters have to span 15 ½ ft. The material will be Douglass Fir. They will cantilever out 2 ft at each end. I think I can use 2x10’s if I space them 16” O.C. or 2x12’s at a 24” O.C. spacing. Does this sound correct?
• Beams – Would a 6x10 carry those rafters if the post spacing is 14 ft? If not would a 6x12 do it?
• Footings – My soil is pretty much clay. I plan on using a cast in place Simson CBSQ66 column support. If I had unlimited funds I would use a Simpson MPBZ but they are very expensive. Is 18” dimeter concrete foot big enough?

I realize it is difficult to exact information but just a ballpark estimate would be helpful. Thanks in advance for any insight you might have.

 

[3Ts]

I can't comment on what you're planning as to whether it will work or not. And we don't have snow loads or freezing ground here in Texas. However, my house is on a slab with a perimeter footer that's 1' wide and 2' tall. The porch consists of 4" steel columns spaced 14' apart with 3 spans (don't know the thickness of the steel). And a wood beam sitting on top of that made up of 3 - 2x12s that are nailed together. The 2x12s are 22' long so they meet and overlap in the middle span. The 3rd 2x12 ties the cantilevered ends together. So, i've got essentially a 4.5"x12"x42' beam - sort of.

 

[EddieWalker]

Why is this going to be free standing? If you attach it to your existing building, it will be a lot stronger.

Putting your posts on top of the concrete footings will make it harder for you to deal with racking. Setting the posts in the ground will lock the building in place. The bracket holding the post on top of the footing will act like a hinge that will require additional bracing to lock the structure in place.

2x10's are fine for a 16 foot span, but I would block them in the center of the span.

I'm not sure what you are referring to for your beams? is a 6x10 the size of a single piece of lumber? or are you going to use four 2x10's to get six inches thick?

For each 14 foot span, I would use two 2x12's with plywood glued between them, and nailed every foot, top and bottom, the full length of the beam. Of spend more money on a Glulam beam.

 

[chris the wrench]

Call your municipality(county or city) and give them your parcel number, they will give you your snowload. Even without needing a permit, thats critical. Then check a span chart. Take the guess work out.

Span Options Calculator for Wood Joists and Rafters

awc.org

Your 18” piers maybe overkill if you are using 6x6 posts. Id look at a 18” footing with a 12” pier. Ive built quite a few buildings like that and we usually auger 18”. Pour 1.5 sacks, let it set and then drop a 12” sonotube on top and align them all. Then backfill gravel.

Ive never built a building like that with 14’ post spacing. 8-10’ is what ive done. Usually double up on my beams notched into the 6x6 posts.

And I’d second the earlier post regarding tying into existing structure, why are you not?

 

[rather]

Sorry I have not posted to your responses on my questions earlier. Thanks for your responses.

The reason I don’t want to tie into the existing structure is that the existing structure has been designed and built with an attic truss that would allow me to add a 16x40 living space. The designer that designed that building warned me against adding additional loads to the buildings foundation because the county may not approve of adding the additional living space when I choose to do so.

When you are talking about tying into the existing building, I am assuming you are talking about a ledger board attached the building and carrying the rafters. Is there another way to do it that does not load the foundation of the existing building. There will be a partial wall in the back of the building to help with racking.

As for putting post in the ground I really don’t want to do that. We live in an area that gets a good bit of rain and I would rather keep those posts out of the ground.

As for the beams I was talking a solid wood 6x10, however this week I found some 6x12 #2 Doug Fir beams on Craigslist for a good price. I think they are overkill but I saved a few dollars.

On the rafters I have checked with the county and snow load in my area is 25 pounds sq/ft. Using the table Chris provided 2x10’s should work.

Right or wrong I am going with 18” round footings. I may make the center footings a little larger. I start digging today.

 

[chris the wrench]

The designer that designed that building warned me against adding additional loads to the buildings foundation because the county may not approve of adding the additional living space when I choose to do so.

Just to confirm the county does NOT require a permit for this current structure you are building, and they will be ok with zero set back from an existing building? I ask because if you plan on bringing an inspector out later for your conversion, having a non-permitted structure in the vicinity may not be great.

I start digging today.

Heck yeah, get after it!

 

[EddieWalker]

I've never heard of a building with a foundation that wasn't strong enough for a lean-to being attached to it. It must be something based on your location. To me, the strength gained by tying the two structures together is significant.