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Free starting design ยท Corrugated gable greenhouse

8x12 Corrugated Greenhouse Plans

96 sq ft of floor, 6/12 gable roof

10 of 10 planner checks passed
The 8x12 gable greenhouse, drawn by the greenhouse designerThe 8x12 gable greenhouse with its footprint and overall heightThe frame of the 8x12 gable greenhouse, without the polycarbonateInside the 8x12 gable greenhouse, two walls cut away to show the benches
Drawn by the designer from this plan
Customize this design, free

As drawn, at 20 psf of snow

Footprint
8x12 ft
Glazing
Corrugated
Vents
5 roof, 6 side
Benches
2 x 24"

About $2,853 in materials, before sales tax, delivery and tools.

Building it? The $29 builder's plan dimensions every stud, sheet and cut. See sample sheets

Planner checks

10 applicable rated checks passed for this configuration.

Site-specific requirements are not fully assessed. The checks size the structure and the vent openings at 20 psf of snow; they do not predict the temperature or humidity inside. Each bar is what this design asks of a part against its limit: the rafter span, the snow the sheets are tabled for, the vent area or fan airflow, and the aisle. The open part of the bar is room this design does not use.

  • Rafter span, 2x43' 8-1/2" of 8' 2-11/16" allowed55% of the allowed span unused at 20 psf; deflection governs
  • Snow on the glazing20 psf of about 50 psf in the maker's table60% of the tabled load unused for this sheet
  • Roof vents23.3 sq ft for 19.2 sq ft needed24% of the floor; the rule asks 20%
  • Side vents22.5 sq ft for 19.2 sq ft needed23% of the floor; the rule asks 20%
  • Aisle37" for 24" suggested13" wider than the suggested aisle

what this design asks room to spare

Green meets the maker's table or the extension guide we checked against, amber asks you to confirm something before you buy, red is outside it. Planner checks don't replace your local building department or a look at your own site.

Specification

The 8x12 gable greenhouse, part by part.

The greenhouse

Footprint
8x12 ft
Floor
96 sq ft
Roof
6/12 gable
To the ridge
8' 6-7/16"

The frame

Rafters
2x4 at 24"
Studs
2x4 at 24"
Base
4x4 on gravel
Roof supports
24" max apart

Cost and time

What it takes to build.

Greenhouse materials, before the gravel bed$2,852.73

  • Polycarbonate and profiles$1,132.94
  • Frame lumber$836.71
  • Vents, door and hardware$781.30
  • Base$101.78

Shelf prices from Home Depot, Hamilton Mill store; Greenhouse Megastore; Lowe's, Atlanta-Edgewood store; Home Depot, Bronx Terminal store; Sturdi-Built Greenhouse; Amazon.com, shipped, read Sep 30, 2026 to Oct 13, 2026. Before sales tax, delivery and tools.

Per sq ft of floor
$29.72
Gravel bed, separate
est. $56 to $186
Build time
46 to 66 h
one handy person with a helper (our estimate)
If you hire the build
$2,300 to $6,600
Separate from the materials.

Prices differ by store and by week: change any line in the greenhouse cost calculator to get your own total.

Free and paid, side by side

Design it free. Build it from the $29 plan.

Free

On this page and in the designer, no account

  • This design in 3D, and every change you make to it
  • Every planner check, with its rule and source
Cost estimate
About $2,853 in materials, line by line, on this page. See the estimate
Summary PDF
The design, its checks and its materials list on a few pages. A summary, not the build drawings.
Customize this design, free

$29 once

The drawings you build from, for the design you finish. About 30 to 45 Letter sheets, 36 for the 8x12 gable greenhouse.

  • Every wall framed, each stud and girt dimensioned from the corner
  • Every polycarbonate sheet numbered, with its cut and the stock sheet it comes from
  • The cut list, every cut assigned to a store board
  • Vents or the exhaust fan, the door and the benches, each on its own sheet
  • The shopping list with store prices and the build, phase by phase
Get the $29 plan for this design

You check out in the designer, with this design loaded. If the plan has an error, we fix it or refund you within 30 days. Guarantee terms.

Real sheets from the 36-sheet sample plan for the 8x12 gable greenhouse

The sample was printed on an earlier date, so its prices can differ from the estimate above. Your plan prints the same prices as the estimate.

  • Sample sheet 17 of 36: wall framing

    Wall framing

  • Sample sheet 23 of 36: sheet layout

    Sheet layout

  • Sample sheet 11 of 36: cut list

    Cut list

  • Sample sheet 33 of 36: build sequence

    Build sequence

Build phases

From gravel bed to the last vent in 6 phases.

About 46 to 66 hours for one handy person with a helper (our estimate). Each picture is this design at the end of its phase, drawn by the designer, with that phase's parts in full color.

  1. The 8x12 gable greenhouse after phase 1: gravel bed and base

    01

    Gravel bed and base

    Level the gravel bed, lay the treated base timbers, square them and anchor them. Check: diagonals equal within 1/4 in, base level.

  2. The 8x12 gable greenhouse after phase 2: wall frames

    02

    Wall frames

    Frame each wall flat, stand it, plumb and brace it, then screw the corners and the bottom plates to the base. Check: corners plumb both ways, top plates level.

  3. The 8x12 gable greenhouse after phase 3: roof frame

    03

    Roof frame

    Set the ridge, rafters, ties and purlins. Paint the frame white before any sheet goes on. Check: rafter tops in one plane: a string along them touches each one.

  4. The 8x12 gable greenhouse after phase 4: door and benches

    04

    Door and benches

    Hang the door and build the benches while the house is still open. Check: door swings clear, benches level.

  5. The 8x12 gable greenhouse after phase 5: corrugated panels

    05

    Corrugated panels

    Walls first, then the roof from the door end, each panel lapped one corrugation and screwed on the crowns. Check: every hole pre-drilled, washers snug, not crushed.

  6. The 8x12 gable greenhouse after phase 6: vents and auto openers

    06

    Vents and auto openers

    Hang the vent lids and fit the automatic openers. Check: each lid closes flat and opens fully.

This is the summary. The $29 builder's plan breaks these phases into a build order with the new parts highlighted, a how-to detail and a check at each step.

The guide to building a greenhouse walks through each phase in general terms.

Questions

Anything else? Write to us or read how the planner checks a design.

Questions about the 8x12 plan

For this design the priced materials come to $2,852.73 at the store prices on this page, before sales tax and freight. The gravel bed is estimated apart, at $56 to $186. If you hire the build, published hourly rates times our hour estimate give $2,300 to $6,600 for labor. The total moves with the size, the glazing and the vents you pick in the designer.

We have not priced kits, so we cannot say which is cheaper for you. What we can say: building this 8x12 yourself from the plan costs $2,852.73 in priced materials plus your time. Compare that with a kit of the same floor area at its delivered price, and check what the kit's glazing and frame are rated for.

It depends on your town. The model building code exempts small one-story accessory buildings up to 200 sq ft, and this design is 96 sq ft, but many towns use a lower limit or treat greenhouses differently, and setbacks still apply. Ask your building department before you order materials.

This design uses 5 roof vents (23.3 sq ft of opening) and 6 side vents (22.5 sq ft): cool air comes in low and leaves near the ridge. We draw roof vents of at least 20% of the floor, the ASABE figure cited by extension guides. Wax-cylinder openers open the lids without power.

It is drawn for the 20 psf you see on this page. Corrugated sheets are tabled by the maker to about 50 psf, so the planner turns red above that. Use the roof snow load your building department gives you, and clear heavy snow after storms.

Sizes to compare

All 11 free greenhouse plans

Ventilation, as drawn

Where the vents go.

Roof vents near the ridge let warm air out; side vents above the benches let cool air in. On a gable the two long walls have room for every side vent the floor needs.

This gable, 96 sq ft of floor
The 8x12 gable greenhouse with its vents in color, drawn by the designer
Vents of the 8x12 gable
VentsCountOpening
Roof vents, both slopes523.3 sq ft
Side vents, both long walls622.5 sq ft
Side vents, end walls00 sq ft
Roof, drawn / needed
23.3 / 19.2 sq ft
Sides, drawn / needed
22.5 / 19.2 sq ft

We draw roof vents of at least 20% of the floor and side vents of at least 20%, the ASABE figures cited by UConn and Alabama Extension. Areas are the openings in the frame; how much air moves also depends on how far each lid opens.

Your greenhouse, your numbers

Make the 8x12 yours.

Change the size, the roof, the glazing, the vents and the benches. The roof supports, the vents and the materials list follow every change. Free, no account.

Customize this design, free
Designing
Free
Builder's plan
$29 once
Account
Not needed
Inside a wooden greenhouse: slatted benches of seedlings on both sides of a gravel aisleIllustration