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Plans for Building a Shed-Workshop

shedworkshop | Posted in General Questions on

Hi, I’m planning out the build of an 8×10 shed / woodworking workshop in climate zone 4A (Virginia). I’d like to use a saltbox style roof and open-joint cladding on the walls. Similar to below, but with taller walls to give the structure a 12ft max height / roof peak:

https://images2.dwell.com/photos/6328431439726800896/6330777385701842944/original.jpg?auto=format&w=1760

Walls: I am leaning toward 16″ OC 2×4 framing with double top plates

Siding: Zip sheathing system covered by Benjamin-Obdyke’s InvisiWrap UV, with UV corrugated plastic battens and vertical, open-joint cedar cladding

Base: 3 4×4 PT lumber skids

Flooring: 2×6″ PT lumber covered by 3/4″ sheathing, covered by pvc or rubber floor mats

Foundation: This is where I could use help. I have an existing 5×7′ concrete slab that I need to build over. I’m learning toward extending it using doweled rebar and an acrylic bonding solution, with the extended portion about 4″ deep, over a 6″ deep gravel base.

Roofing: 7/16″ osb covered by roofing felt and shingles

Windows: whatever sizes I can find at my local architectural salvage shop

How do my plans sound? Any ways I can improve or go greener without raising the costs significantly?

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Replies

  1. Expert Member
    MALCOLM TAYLOR | | #1

    ShedWorkshop,

    - Over time sheds like this often get converted to insulated space. I would design it so this is easy to do.

    - As you aren't really using the slab as a foundation, I wouldn't bother extending it. Just add compacted fill under the area it will occupy and set the PT sills on that.

    - If the interior isn't being finished, you will end up with a lot of nails from the siding and shingles visible (and ready to poke holes in you). Maybe consider strapping or for the roof strapping and another layer of sheathing to hide them.

  2. shedworkshop | | #2

    Thank you for responding! Would I need to box in the compacted fill (3/4" clean stone gravel?) with pressure-treated sides? I see a lot of gravel foundations seem to do that. Imagine that could get tricky with the existing concrete slab in the mix.

    Would R15 Rockwool comfortbatts in the floor joists, wall cavities, and roof joists be enough for insulation if I decide to turn it into an insulated space?

    Good point about the strapping. I'll look into that more.

    1. Expert Member
      MALCOLM TAYLOR | | #4

      ShedWorkshop,

      You only need to contain the new fill if it is a lot higher than the surrounding ground.

      - The main things you need to anticipate if you may insulate later are how you will vent the roof, and how you will get the insulation into the floor and protect the underside.

      -

      1. shedworkshop | | #5

        Good point, I'm starting to think maybe I should just bite the bullet and insulate from the start. Two more questions about the foundation:

        1. Would I want the fill to go all the way up to the concrete slab?

        2. I'll need to elevate the skids if they're partially laying on concrete. Any suggestions on the best way to do that?

        1. Expert Member
          MALCOLM TAYLOR | | #7

          If some part of the skids are sitting on the slab, you can set the rest on either pier blocks or another 4"x4" underneath. Those can bear on the compacted clear crushed gravel, which will help stop frost heave. Another alternative it to remove the existing slab and start fresh on flat compacted fill.

          Maybe just insulate the floor now? It's the one thing that will be difficult later.

          1. shedworkshop | | #8

            It looks like concrete pier blocks or pavers it is. I'm reading pavers can withstand 8000 psi vs 3000 psi for concrete, which has me leaning toward the paver option.

            You're giving me lots to research - I appreciate it.

  3. user-6623302 | | #3

    I think you need to decide ahead of time if you want an insulated floor. You need a plan for the insulation that will keep out moisture and rodents. This becomes a difficult retrofit.

    1. shedworkshop | | #6

      If the skids the subfloor rests on are raised off the ground, that should provide enough airflow to keep the insulation dry right? With hardware cloth. Especially if the majority of the foundation is a gravel base.

  4. canada_deck | | #9

    Am I understanding this correctly:
    You will make an open rectangle out of 4x4 Pressure Treated wood which is resting directly on the ground (e.g. two 10' long pieces and one 8' long piece) and then you will place your floor structure (with the joists and rim boards made of 2x6's on top of that?
    I'll have some comments but would like to confirm that first.

    1. shedworkshop | | #10

      I don't think so. I'm going to put down concrete pavers to rest three 4x4 pt wood on the ground. The subfloor (joists and rim boards) will rest on top of those.

      1. canada_deck | | #11

        Ah ok, more like this as a bird's eye view? blue are the 4*4s and green are the 2*6s? Of course, the blue ones could be perpendicular as well.

        1. shedworkshop | | #13

          Yup, correct! Any advice?

        2. this_page_left_blank | | #15

          They should be perpendicular, I would think.

        3. Expert Member
          MALCOLM TAYLOR | | #16

          I don't understand this whole exchange, I must be missing something.

          Why would two of the 4"x4"s be 10 ft and one 8 ft?

          Why would the 4"x4"s be parallel to the floor joists? They are acting as beams. They should be perpendicular to the floor joists, under the rim-joists.

          1. shedworkshop | | #17

            Malcolm, I was confused by the wording too. I think Canada_Deck misunderstood my earlier question to you about whether I needed a 4x4 retaining wall around the 80 sq ft base of compacted fill and concrete slab.

            Appreciate you and Trevor pointing out the need for the 4x4 skids to be perpendicular. That makes a lot more sense.

          2. canada_deck | | #18

            Yeah I was thrown off by something. This makes more sense.

            I realize this is a fairly common and proven way to do things but my preference is not to have wood (even if it is pressure treated) in constant contact with the ground.

            The alternative is to use concrete piers/footings and then place your beams on those. You don't need the 4"4s then - they will be replaced by the concrete. However, you will need to think carefully about your floor structure because the two long sides are now acting as beams.

          3. Expert Member
            MALCOLM TAYLOR | | #20

            My woodshed is made almost entirely from pt 4"x4"s. If not using those rated for gr0und contact you can alleviate concerns by setting them on a base of free draining clear crushed rock.

  5. wastl | | #12

    How do you want to prevent the shed to be blown away by a strong wind? Some tie-downs seem sensible.. Maybe set some anchors into the existing slab?

    1. shedworkshop | | #14

      Yeah, likely tie-downs. I would've liked to have the whole thing built on screw piles or plastic piers, but the existing slab makes it so those options aren't as viable. I'd rather not have to deal with breaking up / removing the existing slab.

  6. walta100 | | #19

    Am I correct in guessing the sizes of your project is limited by your local ordnances?

    To me 8x10 is so small it is almost unusable a single piece of plywood would be unmanageable unless it is attached to a larger covered patio.

    Often when the rules are so restrictive electricity is also forbidden.

    Some places will allow larger outbuilding but they become taxable structures.

    Seems like this shed is likely to cost several thousands dollar with that money you may want to join the local “makers space” type place. Often you get the use of a large well-equipped heated shop for a few hundred dollars a year.

    Walta

    1. Expert Member
      MALCOLM TAYLOR | | #21

      Walter,

      Small sheds have been a fixture outside houses for centuries.

      I have three 10'x10' sheds. The advantage of building them that size is that as long as they are just used for household storage they are not subject to our building code - although they still have to meet local bylaws.

      They hold tools, gardening and camping supplies, paints and cleaners you don't want in the house. The alternative for many people being to rent storage, which is both inconvenient and costly.

      There is no restriction here, or that I can see in the NEC, on what sized building is supplied with electrical service (you don't even need a building, you can supply a pole if you want). If you limit it to two 15 amp breakers for outlets and lights you don't need a sub-panel.

      1. shedworkshop | | #23

        Malcolm, cool looking design you have there on that shed. Mind if I ask how you did the polycarbonate sidewall and the roofing?

        1. Expert Member
          MALCOLM TAYLOR | | #25

          ShedWorkshop,

          It's a poor picture. That's corrugated galvalum on the walls and snap-lock panels on the roof. Here is a closer detail:

      2. walta100 | | #24

        Malcolm

        I can see to utility of a shed but when the OP calls an 8x10 building a workshop that is when its usefulness becomes questionable to my way of thinking.

        The OP question seems to include some very tight zoning restrictions. The last city I lived in had the same zoning restrictions for temporary building “sheds” mine would not allow any foundation plumbing or electric and be a “shed” My only point is to be sure to understand the rules before you play the game.

        Walta

        1. Expert Member
          MALCOLM TAYLOR | | #26

          Walta,

          "My only point is to be sure to understand the rules before you play the game"

          I agree entirely. Many people only read the first sentence in our building code which says structures under 10 sq.m aren't covered, but the second goes on to say "unless it poses a hazard". That opens it up the the discretion of the building inspector. Our rural area is full of small sheds being rented out as B&Bs by owners who don't know they aren't legal - or covered by their insurance for that use.

    2. shedworkshop | | #22

      Walter, how often are you making things out of an entire plywood sheet? It's easy to rip it to a manageable size with a circular saw, then store it or use it for projects within the shed/workshop. Or I can go with extra large doors and let any overhang extend out the door.

      I can go slightly larger, but then it starts cutting into my yard space. There's something to be said for having a space of one's own to make things in.

      1. Expert Member
        MALCOLM TAYLOR | | #28

        ShedWorkshop,

        I have shop space just up the road, but for small stuff, or when I'm working here at home, I built a Paulk workbench. It breaks down for storage in the rafters of my shed, but set up yields a great work surface outside on sunny days.

        1. shedworkshop | | #29

          Woah well done. I like the look of that. Definitely too big for my needs though : ) I'm leaning toward something simple like this to start out with: https://jayscustomcreations.com/2016/01/build-a-woodworking-workbench/

  7. walta100 | | #27

    Yes I am spoiled to the point that one of my 4 work benches is almost bigger than the shop you are planning.

    I know I would be very frustrated in such a small space but everyone is different just consider how tiny it will be.

    Walta

    1. shedworkshop | | #30

      Maybe one day :) I'll keep it in mind. I always hear to build bigger than you think you should.

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