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?

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