Lally columns can be used outside, but they're designed for dry basements, and most designers prefer sealed HSS steel posts, often galvanized, for decks, carports and other exterior locations. The weak points outdoors are water getting into the pipe or around the plates, and rust starting where the column meets the concrete. Garages and crawl spaces fall in between: they're sheltered, but cold, damp or salty enough that a basement column detail needs some upgrades.
This post looks at steel columns location by location: garages, decks and crawl spaces. The code rules quoted are from the 2024 Ontario Building Code, Part 9. For what a lally column is in the first place, see what is a lally column.
The code rules that apply everywhere
Part 9's column rules (Section 9.17) apply to columns supporting beams under up to two wood-frame floors, under up to two levels of wood-frame decks or one level plus the roof (within limits on joist length and load), and under carport roofs (Article 9.17.1.1). Columns outside those limits are designed under Part 4. Within Part 9:
| Requirement | Rule | Reference |
|---|---|---|
| Location | Centrally located on a footing | 9.17.2.1.(1) |
| Fastening | Securely fastened to the supported member | 9.17.2.2.(1) |
| Lateral support | Laterally supported against racking, with an exemption for short columns under low decks | 9.17.2.2.(2) and (3) |
| Minimum steel pipe size | 73 mm outside diameter, 4.76 mm wall, unless capacity is shown | 9.17.3.1 |
| End plates | At least 100 mm x 100 mm x 6.35 mm at each end; top plate full width of a wood beam | 9.17.3.2 |
| Exterior columns | At least one coat of rust-inhibitive paint where susceptible to corrosion | 9.17.3.3 |
| Adjustable columns | CAN/CGSB-7.2 and no more than 36 kN, otherwise designed | 9.17.3.4 |
Those apply whether the column is in a basement, a garage, a crawl space or under a deck. What changes outside the basement is the environment.
Lally columns outdoors and on decks
Outdoors, a steel column faces rain, snow, freeze-thaw and splash from the ground. The issues with a basement-style lally column are:
- Water in the pipe. A pipe column with an unsealed top or bottom, or a concrete core that has shrunk away from the steel, collects water. It rusts from the inside where you can't see it, and trapped water can freeze.
- Rust at the base. The base plate sits where water, snow and dirt collect. That's where exterior columns usually fail first.
- Coating. Interior columns are often supplied with light paint or primer meant for a dry basement. The code minimum for exterior steel columns is one coat of rust-inhibitive paint, and most exterior columns get much more.
That's why the common exterior choice is a square HSS post with fully welded cap and base plates, so the tube is sealed, finished with a full paint system or hot-dip galvanizing. Our post on steel beams and posts for decks covers the deck-specific rules: deck loads, lateral support for taller posts, and anchorage against uplift. Sizes are in HSS steel posts for basements and decks.
If you do use a round pipe column outside, the same principles apply: sealed ends, a real exterior coating, a base raised on a concrete pier above grade, and a footing below frost depth unless the deck qualifies for the shallow-footing exemption. Our post on whether deck footings need rebar covers that exemption.
Galvanized columns
Hot-dip galvanizing coats the steel in zinc by dipping the finished piece in a molten bath, so it covers edges, welds and, on an open tube, much of the inside. For exterior columns it's one of the most durable finishes. A few practical notes:
- Vent and drain holes. Tubes need holes so the zinc can flow in and out during galvanizing. Those are part of the detail and are sealed or placed where they won't collect water afterward.
- Paint over galvanizing (a duplex system) is common where appearance matters or the exposure is severe.
- Cut ends and field welds lose protection and need touch-up with a zinc-rich product.
For the trade-offs between paint and galvanizing, see does structural steel need paint or galvanizing.
Lally columns in garages
Garages often have a steel column under a beam carrying a room above, a long door header or a flush beam in the ceiling. A basement-type column can work here, with three changes in thinking.
The footing. The garage slab isn't a footing. Footings are required under columns (Article 9.15.3.1), so a garage column sits on its own footing under the slab. Because an attached or detached garage is usually unheated, the footing depth follows the "no heated space" column of Table 9.12.2.2, which in most Ontario soils means going below frost depth. Retrofitting a column into an existing garage means cutting the slab and pouring a proper footing, as covered in lally column footing requirements.
Salt and water at the base. Cars bring in snow and road salt, and the meltwater runs across the floor to the column base. A base plate sitting at slab level in salty water will rust. Common fixes are a concrete pedestal that raises the base plate above the slab, a better coating (galvanizing or a full paint system), and sealing the joint between the plate and the concrete.
Impact. A column beside a parking space or near the garage door can be hit by a vehicle. Part 9's column rules don't size a column for that, so talk to your designer about protection, such as a bollard, a curb or locating the column where cars can't reach it.
Lally columns in crawl spaces
The OBC defines a crawl space as a space under a floor with less than 1 800 mm of clearance to the ground cover (Article 9.18.1.1). Columns in crawl spaces carry the same loads as basement columns, but in a tighter, often damper space.
- Short heights. Crawl space columns are short, sometimes very short. Many adjustable steel columns have a minimum height, so a telepost may not fit. Short fixed steel posts made to length, or concrete piers, are the usual answer.
- Moisture. Unheated crawl spaces are vented to outside air (Article 9.18.3.1), and many stay damp. Steel there benefits from a good primer and paint, or galvanizing, and a base that sits on a footing or pier above the ground cover.
- Footings. Columns are centred on footings (Article 9.17.2.1) that rest on undisturbed soil, rock or compacted granular fill (Article 9.15.3.2). A plate sitting on the ground cover or a loose block isn't a footing.
- Access. Getting a footing and a column into a low crawl space is hard work. That's another reason short, light, pre-made posts are popular here.
If a crawl space has wood posts that have rotted, steel is a common replacement. Our post on lally column vs wood post compares the two.
Which column for which place
| Location | Typical choice | What to watch |
|---|---|---|
| Dry basement | Lally column, telepost or HSS post | Footing, plates, fastening |
| Heated crawl space | Short fixed steel post | Minimum height, footing, access |
| Unheated or damp crawl space | Short fixed steel post, painted or galvanized | Moisture, base above ground cover |
| Garage | Steel column on its own footing, raised base | Salt, frost depth, vehicle impact |
| Deck or carport | Sealed HSS post, galvanized or fully painted | Water traps, lateral support, uplift, frost |
Steel posts made for the location
We fabricate HSS steel posts with welded base and cap plates, cut to the height on your drawings, drilled for anchors and beam connections, and we can prime or galvanize them to suit the location. We supply and install basement beams and posts and deliver across the GTA and Ontario. Send us your drawings or post heights for a quote, or see the steel posts we fabricate.
Frequently asked questions
Can lally columns be used outside?
They can, but they aren't the best choice. Lally columns are made for dry basements, and outdoors the open pipe and concrete core can trap water and rust from the inside. Exterior steel columns in Ontario need at least one coat of rust-inhibitive paint, and most designers use sealed HSS posts, often galvanized, instead.
Can I use a lally column in a garage?
Yes, garages commonly have steel columns under beams that carry a room above or a long header. The column needs its own footing, not just the garage slab, and protection from road salt and vehicle impact at the base.
What kind of post goes in a crawl space?
Short steel posts with welded base and cap plates, or concrete piers, on proper footings. Crawl spaces are often damp, so posts there benefit from a good coating, and many adjustable columns can't be shortened enough to fit low crawl spaces.
Are galvanized lally columns better outdoors?
Galvanizing protects the outside and, on a hot-dipped tube, much of the inside. It is a good choice for exterior and damp locations, especially combined with sealed ends. Ask your designer whether the column also needs paint over the galvanizing.
