Help building first shed

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Forum topic by Dan357 posted 03-18-2018 06:37 PM 1028 views 0 times favorited 25 replies Add to Favorites Watch
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3 posts in 925 days

03-18-2018 06:37 PM

Topic tags/keywords: question

Hello, I’m sorry if I’m posting this in the wrong forum, I need help with my first big project and am not sure where to ask.

I’m building a 12×20 shed, in northern VA, in the city. I have contacted the city office and can build this size without a permit if I follow the setbacks.

My question is, I don’t know how to configure the sub floor. – Wood

I don’t know if I need to frame it with 2×6 or 2×8, or how it should contact the ground. On skids, or set the frame on leveled concrete blocks.

The last question is what do you do for the long 20’ side? Can you buy a 20’ 2×6 at Home Depot? I don’t see it on the website. Or maybe you build 2 12×10 frames and connect them?

I have done much research, but I’m just unclear about how to start the subfloor/ frame.

If anyone can give me some tips on the best way to do this I would really appreciate it.

I’m not very experienced, and I don’t have a huge budget. I just want to do it right.
Thank you

25 replies so far

View John Smith's profile

John Smith

2688 posts in 1018 days

#1 posted 03-18-2018 06:48 PM

Dan – something of this magnitude, I strongly suggest you hire an experienced
contractor just for the initial form setting and basic information.
spending some money for information and assistance up front may save you from
many tears, heartbreaks, time in money in the long run.
getting off on the wrong foot in the wrong direction could be disastrous later.
also – try to find a set of plans or blueprints to work from to avoid serious problems.
not knowing your soil conditions, frost level, etc. is also an issue for accurate feedback.
good luck in your endeavors !! [and always work safely].
for online help: google ~ “how to build a shed” and “shed plans”.
also, your roof must be constructed to support any anticipated snow/ice loads for your area.

-- there is no educational alternative to having a front row seat in the School of Hard Knocks. --

View BlasterStumps's profile


1795 posts in 1295 days

#2 posted 03-18-2018 07:06 PM

Providing logistics will work out, my suggestion would be to contact a shed building company and have them quote you a ‘turn-key’ shed, delivered. You will probably find out they can build it cheaper, faster and with good quality. What if any large things will you have on the floor? I store my garden tractor plus a couple other large items in ours so the floor has an added layer of chipboard. I can run my bigger Fords in there as well. Otherwise, it has 2×6 joists 16” OC over 6×6 skids at 48” spacing and sits on gravel pad. All I did was buy the gravel and spread it out level where I wanted to have the shed set then the shed builder brought the completed shed out on flatbed and set it off on the pad. Done.

-- "I build for function first, looks second. Most times I never get around to looks." MIke in CO

View Mike_D_S's profile


605 posts in 3070 days

#3 posted 03-18-2018 07:12 PM

This is not an overly ambitious project for a medium experience DIY’er with the following restrictions:

1. Hire a contractor to pour a concrete slab for your shed fit for local codes. After considering the labor and materials cost (that’s a lot of pressure treated wood) to level your site, set proper footers (sleepers or block) and build the floor square and level, my gut feel is that your cost to have a concrete slab is probably not much more.

2. Buy plans. Proper design of the framing and roof structure is important. The $50 you spend on quality plans with an accurate materials and cut list will pay for itself in less waste.

3. Buy plans. (See what I did there, I put it in twice because it’s important)

4. Have a helper or two. A lot of this work is going to be too heavy and potentially dangerous work for one person.

Be prepared for the cost. I haven’t done the math exactly, but I’m guessing that here in Houston with a poured 6” slab this would be approx $15 to $20/sq ft to build out.


-- No honey, that's not new, I've had that forever......

View bondogaposis's profile


5844 posts in 3206 days

#4 posted 03-18-2018 07:41 PM

I’m not very experienced, and I don’t have a huge budget. I just want to do it right.

I highly recommend that you purchase some plans. Since you really don’t know even how to begin there will be many things will not occur to you and will give you problems through out the construction. A good set of plans will have all of this stuff worked out. Here is a link to get you started.

-- Bondo Gaposis

View Redoak49's profile


4880 posts in 2844 days

#5 posted 03-18-2018 08:54 PM

I admire your desire to do this yourself but your lack of experience is not good.

I built my own 12×16 shed a number of years ago and it took me a bit and I do have experience.

As others have said, buy some good plans and have someone do the foundation work. I actually poured my own slab and it came out good. It is critical that the foundation is flat and level.

Good luck but get some help.

View Dan357's profile


3 posts in 925 days

#6 posted 03-18-2018 09:00 PM

Hello, Thank you all for the great information. I have a pretty tight budget of $3500 and that’s not enough for a prebuilt in that size.

I will purchase a set of plans and go from there.

I’m lucky that I have a nice set of tools and some good help, I have done many smaller projects around the house but I’m a little lost when it comes to framing a floor this size.

I appreciate your advice.

View Firewood's profile


1302 posts in 2489 days

#7 posted 03-18-2018 09:25 PM


A number of years back, I built a 12×20 shed. I bought plans for a 12×16 shed from The plans were pretty straight forward and I was pleased with the outcome. The big box stores should have 20’ 2 by material for the skirts. I placed blocks on gravel pads to support the floor. I had 2 lawn tractors, a 25ton wood splitter, etc in mine and the floor never moved as far as I could tell.

-- Mike - Waukesha, WI

View John Smith's profile

John Smith

2688 posts in 1018 days

#8 posted 03-18-2018 09:56 PM

not to start the builders war – - – - but, the acceptable practice of joining lumber
is code approved if done correctly. I think you will be very hard pressed finding
a 20 foot P/T board at your Big Box Stores. two skirt boards spliced together will work.
and since you do not need a permit, there is no inspection = your call.
the twelve footers are very common and readily available.

and if you do not have a stick nail gun that will shoot 16d (3”) nails, (and compressor)
now is the time to start searching the pawn shops.
I found a 50lb box of 3” nails at the flea market for $10.00 ~ great find.



-- there is no educational alternative to having a front row seat in the School of Hard Knocks. --

View runswithscissors's profile


3115 posts in 2880 days

#9 posted 03-18-2018 10:43 PM

My dad and I built a slightly smaller shop in a small Washington (state) town. 12X 16, as I remember. No permit required in our case either. We set it on concrete pier blocks, used 2×8 floor joists on 16” centers, T1-11 siding, and a corrugated polycarbonate roof (he wanted the light, but of course it was an oven in the summer). We built the walls flat, and tilted them up into place. The 2 of us barely had the strength to lift those, but he was close to 80 at the time. We did it in 2 days, minus some detail work he did himself. It lasted just fine, and served his needs quite well.

There is no need for your rim joist to be full length. Splices with cleats on the inside are just fine. 12’ is not a difficult span for one-piece floor joists, but a lengthwise stringer down the center would give you a more solid floor. In fact, in that case, 2X6 would be adequate. The center stringer should also be on pier blocks.

Most people nowadays use joist hangers, but they also aren’t necessary. Nailing is adequate.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View Woodknack's profile


13474 posts in 3235 days

#10 posted 03-18-2018 10:43 PM

There are some fantastic step by step shed building videos on Youtube. I don’t mean the Joe Sixpack videos but professionals who show you how to build a shed in a series of videos. Search Youtube for how to build a shed, click on “filter” and choose “playlists”.

-- Rick M,

View GR8HUNTER's profile


7805 posts in 1568 days

#11 posted 03-18-2018 11:05 PM

if going with a stone pad on any elevation make sure to put some pipes in to prevent washout :<))

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN

View duckmilk's profile


4337 posts in 2180 days

#12 posted 03-18-2018 11:13 PM

Runswithscissors is correct, for a 12’ width, the floor will be stronger with a stringer down the center and not flex as much, but you need one or more piers under the center stringer as well. I would use 2×8s for the 20’ stringers and 2×6s for the joists. 2×8s are readily available in 20’ lengths and not much more expensive. Hang the joists between the stringers with galvanized joist hangers.
Make sure that the piers are set on packed ground, and even then, expect some to sink a little, but you can then always add some shims when needed. Piers will keep it off the ground and allow air flow and reduce the deterioration of the wood.
Good luck :-)

-- "Duck and Bob would be out doin some farming with funny hats on." chrisstef

View Knockonit's profile


693 posts in 1057 days

#13 posted 03-18-2018 11:14 PM

I”d go get some 18-20 ga steel studs 6’’ and make floor frame work, set on some supports, block as needed and floor with 3/4’’ t & G, screwed. frame on top, run sheeting down onto floor frame work.

This way when times come to move it, you can crane it, or pick up with jacks and put on rollers and move where ever you want.

If you plan on building not moving, well we all know how that works, moving it is easy, all it takes is a little thought and planning.

I have several on the back half acre. ssteel stud floor frame, 3/4 ’’ plywood, frame with siding coming down, its a fast easy temporary shed. even though they probably wont ever move , but sure like the option. most of my sheds are 10×16 with 8ft side walls, 3-4/12 pitch shingled roof.

good luck, nothing like a new project to get the juices flowing.

-- Living the dream

View 000's profile


2859 posts in 1754 days

#14 posted 03-18-2018 11:22 PM

I built a 20×24 for my dad. Built the front wall taller than the back wall for a sloped roof and used TJI joists for the roof trusses.

View woodbutcherbynight's profile


6183 posts in 3264 days

#15 posted 03-18-2018 11:28 PM

To add to all the above, consider and plan for the proper roof pitch. Here where I am a utility building can have a 3 1/2 inch pitched roof. Simply explained, I am sure we have some roofing experts here, this would be 3 1/2 inches of rise for every foot across. Not really my expertise I usually get my roofing buddy to make sure I have laid it out correctly. But it is important, very important. Under 2 inches of pitch and traditional shingles do not work well and this voids the warranty. Also if you have a decent snowfall then greater roof pitch is needed unless you want the roof to overload and cave in.

Alot goes into building any structure. Sure anybody with a saw, hammer and some time can throw one up, but what issues will you have down the road?

Good luck in your endeavor, plan well, measure twice and be safe.

-- Live to tell the stories, they sound better that way.

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