Inside mount or outside mount is the first big decision with a steel container cover. An inside mount attaches the roof to the inner edges of your containers, covering only the gap between them — it’s lower cost and leaves the container tops open. An outside mount attaches to the outer edges, covering the gap and the containers themselves — it costs more but protects the containers and adds dry storage on top. Both of Toro’s steel container covers — the straight-wall M-Model and the arch-style R Model — are available either way. Here’s how container cover mounting works, and how to choose between inside vs outside mount container covers.
A Simple Scenario to Compare Them
To make the difference easy to picture, imagine two standard 8-foot-wide shipping containers set 30 feet apart. The 30-foot gap between them stays the same no matter which mounting option you choose. The only thing that changes is where the roof attaches — and that changes the cover’s width, its cost, and what ends up protected.
Option 1: Inside Mount
With an inside mount, the roof system attaches to the inside edges of the two containers. In our scenario, the cover spans about 30 feet, the same as the gap. This is the most common of the steel container cover mounting options.
Inside Mount Pros
- Full use of the ground space: The entire 30-foot span between the containers becomes protected working, parking, or storage space.
- Lower cost: Because the cover only needs to be as wide as the gap, it uses less steel and takes less time to assemble.
- Open container tops: The container roofs stay accessible for solar panels, a deck, or stacking materials.
- Tidy profile: With no overhang past the containers, the structure fits well in tighter yards and work sites.
Inside Mount Cons
- Containers stay exposed: Sun, wind, rain, and snow still hit the container roofs and outer walls, so you’ll want to watch for wear.
- Drainage needs planning: Because the roof starts inside the container walls, rain and snowmelt tend to collect along the container tops. Good drainage and regular clearing help prevent rust.
- A less “finished” look: Some owners simply prefer the look of a roof that caps the whole structure.
Option 2: Outside Mount
With an outside mount, the roof system attaches to the outer edges of the containers. In our scenario, the cover spans about 46 feet — the 30-foot gap plus both 8-foot-wide containers. It’s the less common option, but it’s growing in popularity.
Outside Mount Pros
- Protects the containers: Rain, snow, and UV exposure stay off the container roofs, a real advantage for older containers or harsh climates.
- Dry storage up top: The container roofs become covered space for lumber, pipe, or lighter equipment.
- Cleaner drainage: Water sheds off the outer edges of the whole structure instead of collecting on the container tops.
- A finished look: Many owners like how the roof fully caps the structure.
Outside Mount Cons
- Higher cost: A wider cover means more steel and more assembly time.
- Container tops are covered: If you planned a container-top deck or solar array, that space is now under the roof.
- Not always necessary: If your containers are new and well sealed, the added protection may not justify the added cost.
Inside vs. Outside Mount at a Glance
| Factor | Inside Mount | Outside Mount |
|---|---|---|
| Cover width (30′ gap, 8′ containers) | About 30′ | About 46′ |
| Relative cost | Lower | Higher |
| Containers protected | No | Yes |
| Container tops | Open and usable | Covered dry storage |
| Drainage | Needs planning at container tops | Sheds off the outer edges |
| Most common for | Parking, equipment, general storage | Older containers, harsh climates |
How Your Mount Choice Affects Cover Size
Toro container covers come in widths from 20′ to 80′ in 5′ increments, in any length. With an inside mount, the cover width you need matches the gap between your containers. With an outside mount, add the width of both containers — about 16 feet with standard 8-foot containers. That difference matters at larger spans: a 30-foot gap works easily either way, but a 70-foot gap needs a 70-foot cover inside-mounted or an 86-foot cover outside-mounted, which is past the standard range. If you’re working with a wide gap, talk to our team before deciding on a mount.
A Third Option: Inside Mount With Lean-Tos
The straight-wall M-Model adds a third configuration: an inside mount with lean-to extensions along the outer sides. You get the lower-cost inside-mount span between the containers, plus covered space along the outside walls — useful for extra equipment storage or sheltered access to container doors.
How the Cover Attaches
Every Toro container cover has bolt holes built into the base of the roof, so it can be bolted directly to your containers whichever way you mount it. For the arch-style R Model, engineered mounting plates are available as an optional purchase. The M-Model doesn’t use mounting plates; it’s bolted through the base holes or welded to the containers. Your local contractor chooses the best method for your containers, and sealing the connection points against water is part of that job.
The Bigger Picture
The right mount depends less on the roof than on your setup. If you already own the containers, a container cover is usually excellent value. If you’d be buying containers just for this project, compare the cost against a standalone steel building first — see our guide to DIY container cover solutions for the right customer. And before you mount anything, make sure your containers are level, square, and properly supported; our container cover foundations guide covers what to prepare.
So Which Mount Is Right for You?
If you want to maximize the usable space between your containers while keeping costs down, inside mount is the strong choice. If you want to protect your containers and gain covered storage on top, outside mount is often the better long-term investment. Either way, choose the setup that fits your site, what you’re storing, and how long you plan to keep the containers in service.
Permits, Codes & Engineering
Design loads for wind and snow follow the ASCE 7 standard from the American Society of Civil Engineers, referenced by the International Code Council’s International Building Code, or the National Building Code of Canada. Inside and outside mounts transfer loads to the containers differently, so Toro’s in-house engineering team calculates the structural reactions for your specific configuration and site before your cover ships. Toro designs, engineers, manufactures, and ships the cover; you or your local contractor handle the containers, foundation, and assembly.
Related Building Types
Container Covers | M-Model Container Covers: 3 Styles | Why Arch Roofs Are Perfect Shipping Container Covers
Plan Your Container Cover
Toro Steel Buildings can help you choose the right mount and size for your containers and site. Request a free quote to get started.