Building a Shed under a Deck

How to build a shed under a deck. The following youtube video covers some important factors to consider when building such a deck.

I used 3dsmax to model my deck and shed.
I recently converted the 3D deck & shed plans into sketchup so that others can benefit.

Feel free to download the sketchup file and use Google Sketchup to view, measure, and modify my shed/deck plan for your own use.

FREE Google Sketchup Plans for my deck and shed.

Back in 2001 my new home needed a deck. I designed a deck that was small and simple.
The 2 posts and single beam were massive screwed and glued planks.
I am proud of the fact that I single handedly designed and built my deck.
It was a lot of fun figuring out how to lift that heavy, wet, pressure-treated beam onto the posts all by myself.
The posts weren’t small either, when you consider they are almost 6 feet underground!

Overkill should be my new middle name.

Designing my deck with only 2 posts, allowed plenty of space for a shed.
The first stage of building my shed was to build the roof within the joists of the deck.
This stage took a long time and a bunch of thought.
I decided to build an angled trough system with curved sheets of aluminum flashing.

Here you can see the underside and the gradual slope for rain runoff.

This was an incredibly tedious process. I used a large quantity of industrial caulk to seal the aluminum to the joists.
This tedium will be worth it because it maximizes my sheds headroom.
I’m 6′ 3″ and there is just 1″ of headroom from the joists.

The next time I need to cut bricks… I’ll get a diamond blade.
It sure took me a long time to cut them with an abrasive disc.

The shed roof survived the winter and showed no leaks. Now the next stage. I had a concrete pad poured. I decided to put my shed entry on the left side of the deck, so I had to dig the hillside down and create a patio for the doorway. This summer was incredibly hot and moving my sprinkler lines was no fun.

It’s took an eternity to figure out how to build the walls. I had to leave a gap between the walls and the deck. I expected the concrete to heave in the winter.

My excitement is building and I can see the light at the end of the tunnel!

The doorway is short and non-standard. I had to build a custom double door.
Another month or so would pass before I could finish my custom shed doors, but I’m happy with the result. I wanted my shed to look as nice as I could make it… so I wrapped it in matching vinyl siding. My trailer-lift project may have been my most gratifying project, but my shed has been the most useful. Good thing I allowed space for the concrete to heave in winter… because it did just that!

YAAA! My garage is clean and useable again.


  1. February 21st, 2013 at 13:50 | #1

    Great looking project! Looking to do something similar – headroom issues also. How much caulking did you use up? My deck is about 2 1/2 times the size of yours. Looking at roughly 6 rolls of 20″ x 50′ aluminum flashing from Lowes. I covered a portion already that is a storage space.

  2. February 21st, 2013 at 14:12 | #2

    I used quite a bit. Make sure you use NPC Solar Seal Caulk. The best caulk on the planet IMHO. This stuff is used to seal sunrooms, so it can handle the elements. It is super strong and plyable forever. The caulk on my shed has been good for a decade now and I haven’t had to do a thing. Still no leaks. IIbought my caulk from…

    I also recommend a power caulking gun because of the quantity of caulking I was doing was made much easier with a power caulker. I used one by ryobi.

  3. Sam
    February 21st, 2013 at 18:11 | #3

    Thanks for the quick reply! I was trying to gauge how much tubes because I was going to multiply the number by 2 and go from there. Also it looks like you came up with a good cutting scheme to get the aluminum to fit in between the joists neatly and uniformly. My deck is also already in place with deck boards. I have about 11′ x 25 ‘ of usable space under my deck – part of it has a concrete slab – would like to do all – dug it out already and put down gravel. I need a work shop bad – I have a bunch of woodworking tools that I want to put to use – probably could open my own contracting business with all the stuff that is here. My yard could use some curb appeal too! LOL. Thanks again – great work. I do a lot of work by myself too – way too much. Almost done remodeling the interior of my home all by myself. Problem is: now I am about done – what to do with all the tools that have been kept in walkout basement.

  4. vito ginevra
    March 17th, 2013 at 00:15 | #4

    Isn’t aluminum expensive? Is there not a plastic or non corrosive sheet metal that can be used?

  5. March 17th, 2013 at 00:34 | #5

    Actually a roll of sheet aluminum was pretty cheap…. an it should last a very very long time.

  6. vito ginevra
    March 19th, 2013 at 23:30 | #6

    Sorry to bother again. What thickness did you use for the sheet aluminum! Thanks.

  7. Mark
    March 25th, 2013 at 09:31 | #7

    I was planning to do something similar. I just saw a YouTube video where a guy screwed corrugated plastic to the bottom of the deck. He stepped down boards underneath and screwed to those to create a pitch. It seems like a good idea, cheap and easy. Any thoughts?

  8. March 25th, 2013 at 09:34 | #8

    That should work fine and was also my first consideration when I was designing my shed.
    But, I didn’t want to loose headroom in my shed … and I wanted to hide the appearance of a visible roof.

  9. Mark
    March 25th, 2013 at 09:38 | #9

    Wow, quick response. I see what you’re saying about the head room. Fortunately, that should not be an issue with my project. Thanks

  10. Mark
    April 7th, 2013 at 10:46 | #10

    Thanks for the detailed overview of your shed, I plan on working on this project soon. You said that you left room at the top of your walls for heaving of the concrete during winter. Does this mean that the walls are not attached to the underside of the deck?

  11. April 7th, 2013 at 17:55 | #11

    That’s correct… the walls are not attached to the deck. Most people might think that would make the walls flimsy and weak, but if you build all 4 walls and bolt them to a concrete slab… they are very solid and anyone that looks at my shed or pushes on the walls… can’t even tell that it is not connected to the deck. If you live in a cold winter climate like Michigan… do not connect your shed to your deck… IT WILL HEAVE IN WINTER and lift your deck. Over time that can significantly weaken your deck and can lead to catastrophic failure to the ledger board connection to your house. Good luck with your shed design… and please send photos. I’d love to see other designs and techniques. Good Luck.

  12. Shaun
    June 6th, 2013 at 13:16 | #12

    Shed looks great! My deck is not attached to my house. Would heaving be an issue in that case?

  13. June 6th, 2013 at 15:17 | #13

    In my case the problem with heaving… is because I didnt want my shed to lift my deck, which is attached to my house. If your shed is stand alone then heaving is no problem. If your shed is under your deck AND your deck is attached to your house (usually by a ledger board) AND you live in a freezing climate… then you dont want to attach the shed to the deck or house or even build the shed too close to the deck. Because when the shed lifts in the winter from frost heaving… it will lift the deck and greatly weaken the attachment point to the house.

  14. Jerry
    July 10th, 2013 at 12:01 | #14

    Thanks so much for the great video and tons of info. This is exactly what I’m wanting to do under my deck. The difference is that I have a covered deck so not much is needed in way of drainage. I live in Pa. which also has typical winter freezing, but my deck posts sit on the concrete slab. The house is about 20 years old and I suspect the deck was part of original build (also attached to house). There’s no sign of the concrete lifting or cracking. Would you still recommend not tying the walls to the deck or deck posts?

  15. July 10th, 2013 at 13:41 | #15

    I would inspect the ledger board of your deck and make sure the deck attachment to your house has not weakened. A concrete slab will lift and fall every winter/summer. Anywhere from 1/2″ to 1″ movement or more. You may have heard a pop noise during extra cold days in winter? My deck posts go deep into the ground and the slab was poured around the posts with a fiber board relief around the posts. The concrete probably won’t crack when it lifts and falls as entire unit. Ground frost will lift anything that does not go below the frost line (which is 3+ feet underground). My slab lifts more further from the house and less closer to the house, because the house warmth reduces ground freeze nearer the house. Good drainage will also lessen the amount of ground freezing and lift, but there will usually still be some. If your posts are sitting on the slab, there is no reason to not attach your deck to the posts or deck, but I would still be concerned about measuring how much the slab lifts in winter. You could pound a 4 foot+ metal rod into the ground near the slab and mark it where the slab meets. Then check again in the coldest part of winter.

  16. Louis
    August 12th, 2013 at 09:32 | #16

    Great Job! I found your video while doing a google search. I want to pretty much exactly what you’ve done. I live in Prescott, AZ at elevation 5400 ft and we do get below freezing winter temps but not a lot of snow. I’m wondering if I need to follow your advise about leaving a gap between shed and deck and what is the gaps distance? Also, it’s not pictured but I’m curious to know how you finished the top of the deck?

    Thanks Louis

  17. Louis
    August 12th, 2013 at 09:34 | #17

    What size lumber did you go with?

  18. August 12th, 2013 at 10:02 | #18

    I used standard 1×6 deck boards. Sorry to be lazy… but you should read the comment thread above…. it covers the heave issue in detail. My gap is about 1.5 inches and it is very important. Otherwise my deck would be lifted and inch or more every winter and that wouldn’t be good for my deck, downright dangerous.

  19. Dan
    August 19th, 2013 at 16:53 | #19

    I went to the city with a similar idea and was told that a project like this would need some kind of fire prevention / sheet rock between the shed and the deck to minimize chance of a shed fire catching the whole house on fire…were you given any such rules? If so, did the aluminum qualify for the fire break?

  20. Thomas
    September 12th, 2013 at 23:01 | #20

    I built something like this last summer based on your pictures and instructions when I was having my upper deck rebuilt. Used Ice and Weather Shield over the joists overlapping down to the alum troughs to protect the wood. My 16×16′ shop space is nice and dry. My deck is about 3 feet away from the house with a short bridge coming off the back door, so the whole thing is essentially stand-alone.

    BTW, did you ever do anything with your ceiling (I.e. drywall, insulation, etc.) or did you just leave the troughs exposed? I thought about putting foam sheets up on the ceiling to help keep any heat in when Winter comes (I put rocksul in the walls), but styrofoam is pretty flammable I’m told. No room for fiber batts in the ceiling either so not sure what to do there. Anyway, Cheers and thanks for the great idea!

  21. James
    October 3rd, 2013 at 20:44 | #21

    Any concern at all installing aluminum flashing against pressure treated joists? I’m a novice DIY’er looking to do a similar project but it seems fairly unanimous after researching online that aluminum against pressure treated wood will cause the aluminum to corrode and fail. Did you calk the entire side of the troughs to prevent aluminum from contacting the wood?

  22. October 3rd, 2013 at 21:40 | #22

    Great question and excellent point! For any deck built after about 2004, the answer would be YES. My deck was build around 2002 when pressure treated lumber used a different chemistry that did not adversely react with metals. Therefore, anyone doing this now needs to have a barrier between the aluminum flashing and the modern pressure treated lumber OR else it will corrode! Lucky me.

  23. Loretta Dimitroff
    January 17th, 2014 at 21:21 | #23

    Wow, I love your workmanship that’s a fine looking shed. I’m in Australia, myself and another female
    have started our construction course at college. I have always been around construction and thought it was time to get stuck into it, the kids have all grown up and I love. I will be following your projects. Cheers

  24. January 25th, 2014 at 16:18 | #24

    GREAT job on this, brother. I want to do the same thing, but I actually have a stick built room addition above (18X16). I suspect it will be a little bit easier than yours, since there will be no room/drainage issues. Should I still be concerned about heaving with the concrete pad? I just don’t see this thing going anywhere. In theory, I should be able to pour a pad, and start construction on the walls. I think the biggest challenge for me is the slope of my property, which wants to bring water towards the house. But I think a simple French drain can mitigate that. Do you mind me asking how much you budgeted for this project? Again, terrific job! It looks great, and obviously is very functional. Exactly what I need, but I am slow walking the project. ;)

  25. January 25th, 2014 at 16:55 | #25

    Honestly don’t recall how much I spent. The concrete was the most expensive… it cost more than a $1000. The vinyl siding cost a little, but not as much. The rest of the costs were negligible compared to my time spent doing it. If I were to guess… somewhere between 2000-3000 total was spent.

  26. Brian
    February 12th, 2014 at 01:37 | #26

    This is exactly what I have been looking for! How did you complete you’re wall adjacent to the house? It looks like you left the siding that was existing. How did you protect the outside of the OSB against the house?

  27. February 12th, 2014 at 02:07 | #27

    @Brian – I did leave the existing siding on my home. The shed wall was close to the home wall and well protected from the elements by the sealed deck roofing. Once I put the shed siding on and the siding corners.. you can’t even see between the shed and the house. So the outer shed wall facing the home has no siding… it is just the plywood only. The shed is always totally dry … it must be almost 13 years now and the shed still looks great. I do need to refinish the doors because they are looking weathered however.

  28. Ernest
    April 12th, 2014 at 03:01 | #28

    Alan, I love your project. I have been studying your plans and watching your video almost everyday at work. I plan to undertake this project this summer. My deck is pretty high since it connect to the 2nd Flr of my house so I know I will have plenty of headroom plus I’m 5’4” so no issue Anyway, my deck has 3 4×4 posts; will that be ok to build my shed around?

  29. April 26th, 2014 at 12:38 | #29

    Howdy! This is my first comment here so I just wanted to give a
    quick shout out and say I really enjoy reading your
    blog posts. Can you suggest any other blogs/websites/forums that cover
    the same subjects? Thanks for your time!

  30. Ken
    May 3rd, 2014 at 23:23 | #30

    Just a question about the drainage system. Great Idea but how did you seal it from the house and the wall of your shed so the water coming off the house goes down the drainage system you built? Thanks for the video!!

  31. May 5th, 2014 at 20:11 | #31

    I simply used the same flashing… this is the only good photo I have… you can just make out how I shaped a piece of flashing and caulked it will solar-seal. Everything is still totally dry :)

  32. Claypotts
    May 19th, 2014 at 21:32 | #32

    Nice shed! I’m doing one almost exactly the same in 2 weeks when I take possession of my house. My deck is about the same size as yours. I’m adding a small landing at the top and a staircase that goes parallel to the rim joist furthest from the house.
    I will be pouring a pad much like yours. You mentioned that you used a “fibre board relief” around the posts so that the slab moves independently of the posts. Can you explain that process a bit more for me? Not only will I have the 2 deck posts, but I will have 6 more sonotube posts supporting the landing and staircase. Thanks in advance
    My other thought is to pour the pad with submerged sonotubes where the landing/stair post will be. Technically, that would give each post (and perhaps the entire pad) footings that will prevent heaving….btw I live in canada where the frost line is 48″ by code.

  33. JD
    May 24th, 2014 at 14:07 | #33

    I also admire your shed. Looks beautiful. How did you attach the plywood for the side wall without any room between it’s framing and your house exterior?

  34. JD
    May 24th, 2014 at 14:11 | #34

    I retract my question. I did not realize there was another entire page of comments. Again, great work.

  35. May 24th, 2014 at 16:00 | #35

    Thanks JD… a shed under deck is a popular idea. Finally time this year to remove my doors and refinish them with epifanes boat varnish. That stuff lasted a long time, but even a boat varnish won’t last forever.

  36. JD
    May 24th, 2014 at 21:15 | #36

    edit: the question actually wasn’t answered previously after all.

  37. May 24th, 2014 at 22:51 | #37

    I left the existing siding on my home. The shed wall was close to the home wall and well protected from the elements by the sealed deck roofing. Once I put the shed siding on and the siding corners.. you can’t even see between the shed and the house. So the outer shed wall facing the home has no siding… it is just the plywood only. The shed is always totally dry … it must be almost 13 years now and the shed still looks great.

  38. Mike Dotson
    May 30th, 2014 at 16:02 | #38

    Awesome job and I’m right in the middle of copying this set up. But I’m wondering why you put the particle board in between the joists and not just hang the sheeting between the boards and exposed underneath? Thank you for your time!!

  39. May 30th, 2014 at 16:32 | #39

    @Mike Dotson, Thanks… My head just clears the bottom of the joists.. so if I hang anything below them I would always be bent-over while in my shed OR bumping my head. If you have the vertical height or don’t care… it would be easier to build a drop roof below the deck.

  40. Mike Dotson
    May 30th, 2014 at 17:11 | #40

    Thank you so very much for your reply and extremely quick response!! I’m only 5’5″, so hitting anything over my head is not much of a worry for me, lol. So, just to be clear, I don’t need the plywood under the aluminum flashing? All I’d need to do is screw in the aluminum at an angle and seal it off? I don’t intend to ever hang anything from the ceiling either. Wow, would be so much less work than doing the plywood between the joists if I don’t really need too. But, you stated earlier in one of your responses, the wood troughs were to support the “load” and was wondering what you meant by that? This will be my last question I promise….Thanks again!!!

  41. May 30th, 2014 at 20:26 | #41

    @Mike Dotson… Oh I misunderstood your original question. In my case, I felt the plywood was necessary because the plywood helped me control the positioning and ensure the strength of the aluminum sheets which I only lightly stapled every few feet and then applied caulk to seal the aluminum flashing the the joist. Without the plywood… I would not expect the longevity I’ve gotten so far… which is around 10 years now. It was tedious to install, but I’m a patient sort of guy :). Plus I feel the overall look is more complete and finished looking.

  42. Mike Dotson
    May 30th, 2014 at 23:17 | #42

    You can tell you are very patient and very meticulous!! I built my shed under half of my existing 400sqft deck at the end of last summer and my ideas on how to keep the water out wasn’t even close to doing it right. When I came across your video, I was like, I love the internet!! Your answer this time was exactly what I was wanting to know and I’m confidently on my way. I can’t thank you enough for taking time out of your day for the help!!!!

  43. Casey
    June 4th, 2014 at 15:43 | #43


    I have a deck almost identical to yours (both in terms of size and how it is supported). I’d have more headroom, and the deckboards are already on, so I am thinking of putting the roof below the joists as opposed to between the joists as you did. If you were to have done that, which you said you likely would have were you not concerned about headroom, would you have made your shed smaller? The reason I ask is because I am not sure how I would keep the roof below the deck joists (likely using the corragated metal or fiberglass) and at the same time have the posts that support the deck inside the shed as you did. Any thoughts?

  44. sidney
    June 13th, 2014 at 04:39 | #44

    Hi, We are building a deck and want a storage underneith it. I have some questions. How do you clean the aluminum gutters? Do they get moldy and has the shed stayed dry??

  45. June 13th, 2014 at 09:06 | #45

    @sidney… I don’t clean the aluminum, they stay clean on their own by the occasional rainfall and the fact that we have no trees around our deck. No mold at all. And YES the shed is 100% dry inside … even after many years and several high wind rain storms. Super dry … I love my shed. I do finally need to refinish the shed doors this year though, but that’s to be expected.

  46. JD
    June 13th, 2014 at 10:39 | #46

    I guess what I was asking is, with no room between the exterior wall of your house and the exterior wall of your shed to walk or swing a hammer, how did you attach the “back” plywood wall to the shed’s studs? Thanks again

  47. June 13th, 2014 at 10:49 | #47

    @JD, in the picture where I’m sitting in a chair … doing calculations.. I had built the stud framing, but I hadn’t bolted them to the concrete or permanently fixed the walls yet. Because I wanted to do a dry fit and evaluate next steps in the construction. Then I laid the back wall down and attached the plywood and then put it back up. Then I put all the other walls up and finished the plywood, the window, doors, and siding. I have since added a gutter at the end and I need to refinish the doors… so I will probably do a video update and try to cover many of these types of questions in the video.

  48. JD
    June 13th, 2014 at 12:23 | #48

    I wondered if that might be how you did it. Looking forward to the video update! Thanks again for sharing with everyone. Very inspiring and helpful.

  49. J-Low
    July 1st, 2014 at 08:38 | #49

    Great build!

    Where are you located? I am wondering about the concrete heaving. My mason poured a pad under my deck and asked if the concrete was going to heave in the winter. He said, “I wouldn’t worry about it.”

    My plan is to do board and batten that is attached to my deck and run in clear to the concrete and up to the deck joists. However, I have to add two additional 4x4s or 6x6s near the house at the corner of the concrete to give my board and batten something to be fastened to. I would attached the top of the new post to the joist of the deck and anchor the bottom of the post to the concrete.

    Do you see any harm in this? What are your thoughts?

  50. July 1st, 2014 at 09:36 | #50

    @J-Low… I live in Michigan. Heaving concrete is nothing to worry about IF you are not going to attach the concrete in any way to your deck. But, if you do AND you live where the ground can freeze… then you should worry. If the ground freezes enough in winter… the concrete will heave (more further from your home and less closer to your home) and NOTHING can stop it from heaving, not even a strong deck. Solid ice can lift 10-20 tons per square inch. An elephant weighs 8 tons. Even though the moisture is mixed with soil… it will still have no problem lifting your shed and deck or crushing it until something gives. My shed is not attached to my deck in any way.

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