A new concrete-filled lally column is cut to length by scoring all the way around the steel shell with a heavy-duty pipe cutter, snapping the column, and trimming the concrete core flush, or by cutting straight through with a reciprocating, abrasive or band saw. The cut has to be square so the column bears evenly on its plates, and the length has to allow for the plates and anything else in the stack. Never cut a column that is already carrying load, and don't cut an adjustable steel column unless its manufacturer allows it.
Cutting is the easy part. Getting the length right, getting a square end and connecting it properly top and bottom are what decide whether the column does its job.
Before you cut: the column is structural
A lally column carries the beam, and the beam carries the floors above. That makes the whole job structural, not just the cut.
- A loaded column stays uncut. If an existing column is the wrong height, rusted or in the wrong place, the beam is shored on temporary supports first and the old column removed before anything else happens. Our guide on how to replace lally columns walks through the sequence.
- A new or moved column usually needs a permit and a footing. The 2024 Ontario Building Code requires columns to be centrally located on a footing that conforms to Section 9.15. A basement slab isn't a footing, so a new column location usually means cutting the slab and pouring a pad footing. See lally column footing requirements.
- The size comes from the load. Part 9 sets a minimum for steel pipe columns of 73 mm outside diameter and 4.76 mm wall thickness, unless another size is shown to have enough capacity. Which column you need is for your designer to confirm.
Cutting a column to length belongs in the installation sequence described in how to install a lally column in a basement. This post covers that one step.
How to measure a lally column
Measure at the exact spot the column will stand, not at the nearest wall. Floors and beams are rarely perfectly level.
- Establish the bearing surfaces. The bottom is the top of the footing or the surface the base plate will sit on. The top is the underside of the beam, or of the wood plate under a wood beam.
- Measure the clear height. Take the distance between those two surfaces with the beam at its intended level. If the beam is being jacked back to level, measure after it has been raised and is sitting on shores, not before.
- Subtract everything in the stack. Deduct the thickness of the base plate, cap plate and any steel shims or grout layer. If the column will sit on a grouted base, include the grout thickness in the drawing.
- Check at two faces. Measure on opposite sides of the column location. A large difference means the beam or footing isn't level and the plates or shims need to deal with it.
Steel columns need end plates at each end. Article 9.17.3.2 of the 2024 OBC calls for plates of at least 100 mm by 100 mm by 6.35 mm thick, with the top plate extending across the full width of a wood beam. The top plate can be omitted where the column supports a steel beam and provision is made to attach the column to the beam. Our guide to lally column cap and base plates explains the options.
A column cut a little short and shimmed with steel plates is usually better than one forced in too long. Wood shims crush, and an over-length column can lift the beam and the floor above.
How to cut a concrete-filled lally column
A traditional lally column is a thin steel tube filled with concrete. The steel shell has to be cut cleanly, and the concrete core has to be broken off flush.
Method 1: pipe cutter and hammer
This is the classic site method.
- Mark the cut line all the way around the column with a wrap of tape or a paper band so it's square.
- Clamp the column so it can't roll.
- Fit a heavy-duty wheel pipe cutter sized for the column diameter and work it around, tightening a little each turn, until it cuts through the steel shell.
- Strike the column near the cut with a heavy hammer to crack the concrete core, and snap the off-cut away.
- Chip or grind the concrete back so it is flush with or slightly below the steel, and file off any burr on the shell.
The pipe cutter gives a square, clean edge on the shell, which is what bears on the plate.
Method 2: saw cut
A reciprocating saw with a metal-cutting blade, an abrasive cut-off saw or a band saw can cut through the shell and core together. Saws cut faster through hollow pipe but wear quickly on concrete, and a hand-held saw makes it harder to keep the cut square. Cutting concrete makes silica dust, so wear eye, hearing and respiratory protection and control the dust.
Checking the cut
Check the end with a square in two directions. A cut that's off square means the column bears on one edge of the plate, which concentrates the load and can let the column lean. Grind it true before installing.
Adjustable columns and teleposts
Adjustable steel columns (teleposts or jack posts) are different. They're made in length ranges and adjusted with a threaded screw, not cut. Under Article 9.17.3.4 of the 2024 OBC, adjustable steel columns for imposed loads up to 36 kN have to conform to CAN/CGSB-7.2, and others have to be designed under Part 4. Cutting the tube or extending the screw beyond its range takes the column outside what it was tested for.
If an adjustable column is too short or too long for your basement, get the right model or a fixed post instead. Our post on whether adjustable steel columns can be permanent explains where they fit.
Fixed steel posts cut in the shop
In Ontario, many permanent basement columns aren't concrete-filled lally columns at all. They're fixed steel posts made from round pipe or square HSS, cut to the measured height with base and cap plates welded on in a shop. That approach has some clear advantages:
| Cut on site | Cut in the shop | |
|---|---|---|
| Square ends | Depends on tools and care | Cut square on shop equipment |
| End plates | Fastened or welded on site | Welded under shop conditions |
| Holes for fastening | Drilled on site | Drilled to the drawing |
| Finish | Painted on site | Primed or galvanized before delivery |
| Site work | Cutting, grinding, dust | Set, plumb and fasten |
The trade-off is that the height has to be measured accurately and sent before fabrication. The lally column sizes guide covers the diameters and wall thicknesses you'll see, and our post on installing steel columns and posts covers setting them.
Common mistakes
- Measuring before the beam is level. The column ends up holding the sag in place.
- Forgetting the plates. Every plate and shim in the stack comes off the column length.
- An off-square cut. The column rocks or bears on one edge.
- Loose bottom ends. A column that isn't fastened can be knocked out of position. The code requires columns to be securely fastened to the supported member and laterally supported.
- Cutting a column in place. A loaded column must never be cut, even to "just trim a little."
Get your steel posts cut to length
If you'd rather skip the cutting, we fabricate HSS and steel posts for basements cut to your measured height with base and cap plates welded on, and we can prime or galvanize to suit. We also supply and install basement beams and posts. Send us the height, the beam size and your drawings for a free quote, and see our services for how we handle a job from drawings to installation.
Frequently asked questions
Can you cut a lally column?
A new concrete-filled lally column that is not carrying load can be cut to length before it's installed. A column already supporting a beam must never be cut in place, and adjustable columns shouldn't be cut or altered beyond what the manufacturer allows.
What tool cuts a lally column?
Concrete-filled lally columns are usually cut by scoring through the steel shell with a heavy-duty wheel pipe cutter, then breaking the concrete core. A reciprocating saw, abrasive cut-off saw or band saw also works. Hollow pipe and HSS posts are cut with a saw.
How do you measure a lally column for length?
Measure from the top of the footing, or the surface the base plate will sit on, to the underside of the beam at the exact column location. Then subtract the thickness of the base and cap plates and any shims or wood plate that will sit in the stack.
How long are lally columns?
They are sold in stock lengths longer than most basement heights and cut to fit on site. In Ontario, fixed steel posts are more often fabricated from pipe or HSS to the exact measured height with plates welded on.
