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Free: the 3D model, the checks, the cost and the materials list update as you design. Optional: the $29 builder's plan for the greenhouse you finish.

8x12 gable greenhouseAll checks pass
8' x 12' gable greenhouseAll checks pass for these loadsLocal approval not checkedDesign TGH-ZJCZ-31HY · Plan rev. 1
8'8'12'12'
100%
Floor
96 sq ft
Bench
45.3 sq ft
Vents
11
Sheets
11

Drag sideways to turn the greenhouse. Scroll, pinch or use + and − to zoom.

Build this exact greenhouse: $29

Every wall framed and dimensioned, every sheet numbered and cut, the cut list board by board and a step-by-step build. One PDF, yours to keep.

Materials about $3,814 before tax, about 46 to 66 hours to build (our estimate). Labor if hired: $2,300 to $6,600.

All checks pass for these loads

10 applicable rated checks passed for this configuration. Site-specific requirements are not fully assessed.

The checks cover the frame, the glazing, the vent area or fan size and the layout. Passing them does not predict the temperature or the humidity inside.

Every check passes at 20 psf of roof snow. Local approval not checked: ask your building department about permits and loads.

Size and roof

Roof
Width (gable end)
Length
Wall height
Roof pitch

The buttons move the width by 1 ft and the length by 2 ft, half a 4 ft sheet. Or type any size in the box, from 6' to 20' wide and 6' to 40' long: the planner rounds it to the nearest 6 in.

Glazing

Glazing

Twin-wall sheets on a 4 ft grid, flutes down the slope. Supports at most 24 in apart at 20 psf.

Vents and door

How would you like to ventilate your greenhouse?

Neither price is a complete delivered build cost: tax, freight, gravel and any line we could not price are extra, and the fan option also needs the electrician.

Roof vents

5 roof vents (23.3 sq ft) and 6 side vents (22.5 sq ft), sized from the floor area. No power needed.

Why this many vents?

Extension guidance (ASABE, as cited by UConn and Alabama Extension) puts roof vents at 15 to 20% of the floor area and side vents at the same. Small greenhouses heat up fastest, so we draw the top of the range, 20% each: 19.2 sq ft of roof vent and 19.2 sq ft of side vent for 96 sq ft of floor.

Each roof vent opens 22-1/2" x 29-7/8" (4.7 sq ft) and each side vent 22-1/2" x 24" (3.8 sq ft): that makes 5 roof and 6 side vents. Warm air leaves at the top and pulls cool air in low (Clemson, Oklahoma State). Rather run a fan? Pick Exhaust fan above.

DEF-01 UConn Extension (2013), Alabama Extension (2022), Clemson Extension HGIC 1704 (1999)

Door width

Benches

Benches

Base and site

Base
Roof snow load (psf)
Wind

10 applicable rated checks passed for this configuration. Site-specific requirements are not fully assessed.

  • 10 passed
  • 6 to read

Cost

Materials$3,813.80every line priced, before tax
Labor if hired$2,300 to $6,60046 to 66 h at $50 to $100/h
Lumber
$791.49
Glazing
$1,264.98
Profiles and sealing
$779.20
Gravel, separate
$56 to $186
Not included
tax · shipping and freight
How we priced this

Materials

Prices as read at Home Depot, Hamilton Mill store; PolycarbonateStore.com; Greenhouse Megastore; Lowe's, Atlanta-Edgewood store; Home Depot, Bronx Terminal store; Sturdi-Built Greenhouse; Amazon.com, shipped, between Sep 30, 2026 and Oct 13, 2026, before tax and shipping. Gravel is a sourced range from HomeGuide, crushed stone and gravel prices (Dec 2025), kept apart from the priced total. Not priced: nothing, every line has a price.

Labor if hired

$3,920 at the middle rate of $70 per hour times 56 hours. The range is the published hourly rates of $50 to $100 times our 46 to 66 hour build estimate: 46 hours at $50 to 66 hours at $100 (Fixr, Jan 31, 2025: $70 per hour; HomeAdvisor, Jun 19, 2026: $50 to $100 per hour). A sourced range for building the greenhouse from plans, by a handyperson or carpenter, not a quote, kept apart from the materials. No published guide gives a labor price for building a custom greenhouse from plans, so this is an hourly rate times our build-hours estimate. The hours are ours, for one handy person with a helper.

Gravel

$56 to $186, a sourced range (HomeGuide, crushed stone and gravel prices, Dec 2025), kept apart from the priced total; your quarry or yard quotes the final price.

Not included

sales tax; shipping and freight (twin-wall sheets usually ship by freight: get a delivered quote).

Lumber
$791.49 14 lines
Glazing
$1,264.98 2 lines
Profiles and sealing
$779.20 7 lines
Fasteners and hardware
$326.93 4 lines
Vents and door
$549.42 4 lines
Base and site
$101.78 3 lines
Cut list
243 pieces

What you build from

Builder's plan

$29one payment, no subscription
yours to keep

Every board, every sheet, every cut, every step, drawn for this exact greenhouse.

  • about 35 Letter sheets
  • 46 to 66 h build time
  • $3,814 materials
  • $2,300 to $6,600 labor if hired
  • 4 walls framed stud by stud and girt by girt, measured from one corner, and the door framed in its end wall
  • 14 2x4 rafters with the cut drawn, purlin blocks spaced for 20 psf, 4 rafter ties
  • 16 sheet pieces cut from 11 stock sheets, face by face, with tapes, H and U profiles and screw spacing
Wall framing, a sample sheet from the 8x12 planWall framingSheet layout, a sample sheet from the 8x12 planSheet layoutShopping list, a sample sheet from the 8x12 planShopping listCut list, a sample sheet from the 8x12 planCut list

Sample sheets from the 8x12 plan with natural vents; yours are drawn for this design. The materials figure is priced materials only, before tax and delivery; the full list is in the Cost box.

Plan error guarantee. If our plan has an error, we fix it or refund you. Tell us within 30 days what is wrong and where; we send a corrected plan, and refund you if we cannot fix it. No refunds for a change of mind. Terms

Design TGH-ZJCZ-31HY · Plan rev. 1 · Checks passed for the loads you entered · Local approval not checked

Keep this page's link and the design comes back as it is.

The free summary has the 3D view, the sizes, the checks and the materials list.

Your 8x12 greenhouse plan, about 35 sheets, $29

How it works

Four moves, one greenhouse.

Everything on the drawing is the engine's own output: the same numbers go into the checks, the cost, the summary PDF and the $29 plan.

  1. Your size

    Set the width (6 to 20 ft, or 4 to 12 ft for a lean-to), the length (6 to 40 ft), the wall height and the roof. Studs and rafters land 24 in apart so every 4 ft sheet joint sits on a member.

  2. Sized for your load

    Purlins and girts are spaced from the polycarbonate maker's published load tables for the snow load you enter, never wider.

  3. Vents from the floor

    Roof and side vents are sized from the floor area with the extension rule, then placed in the rafter and stud bays. Or choose an exhaust fan, sized from the air volume.

  4. One list to buy

    Boards, sheets, profiles, tapes, screws and hardware in one priced list, with the cut list behind it.

Planner checks

The rules it checks.

Each check in the panel names its rule and source. Where a source gives a range or says nothing, the value is marked as our default. Permits, setbacks and local loads depend on where you build: ask your building department.

All 7 rules and their sources
RuleCheckWhat passesSources
DEF-01Roof vents20% of the floor area; 15% to 20% is amberUConn Extension (2013), Alabama Extension (2022), Clemson Extension HGIC 1704 (1999)
DEF-02Side vents20% of the floor area, low on the wallsUConn Extension (2013), Clemson Extension HGIC 1704 (1999), Oklahoma State HLA-6705 (2013)
DEF-15Exhaust fan (option)1.5 air changes a minute and at least 8 cfm per sq ft of floor; intake about 1.5 sq ft per 1,000 cfm the fan movesClemson Extension HGIC 1704 (1999), UGA Extension B 910 (2023), Oklahoma State HLA-6705 (2013), UConn Extension (2013), NRAES-33 Greenhouse Engineering (1994), Alabama Extension (2022), J&D, ES fan specifications, UGA Extension B 792 (2025), J&D, shutter and motor kit, Greenhouse Megastore sizing guide
DEF-06Supports for the loadThe smallest spacing in the maker's tables at your load, end spans includedPalram, Sunlite technical guide (2019), Palram, Sunlite greenhouse guide (2021), Palram, Sunlite US instructions (2026), Palram, Suntuf installation guide
DEF-07Roof slopeAt least 2 in per ft for twin-wall, 1-1/2 in per ft for corrugatedPalram, Sunlite US instructions (2026), Palram, Sunlite technical guide (2019), Palram, Suntuf installation guide (2010), Palram, Suntuf data sheet
DEF-04Bench depth30 in when worked from one sideUGA Extension B 910 (2023), Oklahoma State HLA-6705 (2013)
DEF-05Aisle24 in; 18 in at leastUGA Extension B 910 (2023)
  • ED-02 You enter the roof snow load your building department uses. Rafters are sized with Spruce-Pine-Fir No. 2 span math for that load plus 4 psf of dead load, L/180 deflection (our default). Above the glazing maker's table (about 31 psf for twin-wall, 50 psf for Suntuf) the designer does not size the roof: it refers you to the maker and an engineer.
  • ED-03 NRAES (citing NGMA): greenhouses are designed for an 80 mph wind, about 16 psf. We space the wall girts with the maker's table at 16 psf, or at 25 psf (our default) on an exposed site. This is not a wind design: exposed and coastal sites should have the frame and anchors checked locally.

The builder's plan for your greenhouse.

Every wall framed, every sheet numbered and cut, the cut list board by board and a step-by-step build, for the greenhouse you design here. $29 once, from the plan box in the designer. If our plan has an error, we fix it or refund you within 30 days.

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