Metal Lean To Carport: Specs, Cost, Attaching and Freestanding Builds

Carport.com describes the form as one high eave and one low eave, and it uses the term shed-roof carport for the freestanding version. Pro Metal Buildings describes its 12 by 20 foot model as a vertical single-slope roof.

Three ways to site a metal lean-to

A metal lean-to carport can stand on its own posts, sit against the wall of a building, or sit beside an existing building without touching it. The diagram labels each option with the reference number of the seller page that describes it in the sources table.

Pro Metal Buildings says its lean-to can stand alone or attach to existing structures. Carport Central describes a free-standing lean-to as one often installed near an existing structure but not connected to it.

For the general split between the two builds, see attached or freestanding lean-to carports.

Several sources cited here sell metal structures: Pro Metal Buildings, Carport.com, NorCal Carports, Legacy Carports, Alan's Factory Outlet and Eagle Buildings. Their specs, prices and policies are marked seller-published.

Pro Metal Buildings publishes $2,960.00 for its 12 by 20 foot model, and its page states that delivery and installation are included. NorCal Carports starts its lean-to structures around $5,400.

Dividing the $2,960 seller price by 240 square feet gives $12.33 per square foot. That sits inside the $12 to $22 range for lean-tos ordered with a metal building and the $12 to $40 range for installed carports.

What changes the price

Steel Building Kit lists engineering for a retrofit at $800 to $2,500, plus $300 to $800 per revision. It puts a lean-to added later 30 to 50 percent above the order-time price.

Slab costs appear in two guides: HomeGuide lists $5 to $10 per square foot, and Steel Building Kit lists $6 to $12 for a lean-to ordered with a building. Steel Building Kit's page covers metal-building lean-tos, so its ranges describe that product and not a carport kit.

Carport.com says it can add a lean-to to a building it set, after confirming load and attachment. For other buildings, it says confirming engineering falls to the buyer and the inspector.

Steel Building Kit says sidewall columns must be engineered to carry the load transfer, and it lists retrofit engineering at $800 to $2,500. Carport Central says some companies install a lean-to only if they also installed the existing structure, for liability reasons.

Pro Metal Buildings lists delivery and installation in its $2,960 price. Alan's Factory Outlet's guide covers a wood-framed build with 6x6 posts, a 2x6 ledger board lag-bolted to the existing framing and metal roofing, lists no prices, and rates the work advanced.

Dates in the sources table are the dates the sellers and publishers show on their pages. Where a page shows no date, the table says undated and gives the day it was read, October 5, 2026. Prices and policies change, so each figure keeps its own date beside it.

• Roof pitch and snow against a wall: attached or freestanding lean-to carports.
• Permit steps and thresholds: carport permit.
• Gauge and coating: CarportBay's metal carports guide.