Steel jack posts and adjustable steel shores are widely available to rent from tool-rental and equipment-rental stores, and heavier post shores come from formwork and shoring suppliers. They're temporary supports, used to hold up floors and roofs while a wall comes out, a beam goes in or a column is replaced. They are not the same as a permanent lally column or telepost, and the number, spacing and capacity of the shores should come from whoever is designing the work, not from guesswork on the day.
This post explains what you can rent, how rated loads work, how a temporary shoring setup carries load, and what replaces the shores when the job is done. It doesn't replace a design: shoring for structural work is part of the plan your designer, engineer or contractor prepares.
What you can rent
Rental fleets use a lot of overlapping names. The main products are:
| Product | What it is | Typical use |
|---|---|---|
| Adjustable steel shore (post shore, sometimes called an acrow prop) | Two telescoping steel tubes with a pin for coarse height and a screw collar for fine adjustment, with flat plates top and bottom | Supporting floor joists or a beam during wall removal or beam installation |
| Screw jack post | A shorter steel post with a threaded screw at the top | Short-term support under a beam or joist line in a basement |
| Heavy-duty post shores and shoring frames | Larger shores or braced frame towers built for concrete formwork | Heavier loads, taller heights, supporting formwork for suspended concrete |
| Aluminum shores | Lighter telescoping shores, mainly for formwork | Formwork and some renovation work where weight matters |
"Lally column rental" is a common search, but lally columns aren't really a rental item. A lally column is a permanent steel pipe column cut to fit one spot. Our post on what a lally column is covers the differences between lally columns, teleposts and jack posts.
Load ratings: read the table for your model
The capacity of an adjustable shore depends on the model and how far it's extended. A longer post is more slender, so it can buckle at a lower load, and manufacturers publish load tables that show the safe load at different heights. A few rules follow from that:
- Get the load table for the exact model. Ask the rental counter for it. Two posts that look alike can have very different ratings.
- Rated loads drop as the post is extended. A post used near its maximum extension carries less than the same post used near its minimum.
- Plumb matters. Ratings assume the post is vertical and loaded through its centre. A leaning post, or one loaded off one edge of its plate, carries less.
- Check the condition. Bent tubes, damaged threads, missing pins or substitute pins (a bolt or a nail in place of the proper pin) are reasons to send a post back.
This is also why the people designing the job should set the number and spacing of shores. They know the load being held up and can match it to a product's published rating.
How a temporary shoring setup carries load
Shoring isn't just a row of posts. The load has to get from the structure above, through the shores, and down to something that can carry it.
At the top. A shore plate is small. Under floor joists, the shores normally push up on a continuous beam or doubled plate that runs across the joists, so each joist is supported and the load is spread. Under an existing beam, the shores sit directly under it.
At the bottom. The bottom of each shore needs a firm, level base that spreads the load. On a wood subfloor, that usually means a plate or sill across several joists. On a basement slab, it means a pad to spread the load, and a check on whether the slab can take it. Under Article 9.16.4.3 of the 2024 Ontario Building Code, a basement floor slab only has to be 75 mm thick, and it isn't a footing. Concentrated shore loads on a thin slab can crack it or push it down into soft fill.
On floors below. When the shoring sits on a main floor, the load goes into the main-floor joists, which may need shoring of their own in the basement. On multi-storey work, shoring often stacks through the house down to the basement. Our post on removing a load-bearing wall in a two-storey or split-level covers why load paths get longer on upper floors.
Both sides of the wall. When joists bear on a wall from both sides, there's normally a line of shoring on each side. For a flush beam, the shoring is set back far enough to leave room to cut the joists and fit the beam. The full sequence is in our guide to removing a load-bearing wall and installing a beam.
Snug, not jacking. Temporary shores are set to take up the load without lifting the structure. Jacking a floor up quickly to "fix" a sag can crack drywall, plaster and tile, pull nails and damage finishes above. Any lifting is part of the design and done slowly.
Rent or buy?
Most homeowners and small renovators rent because the shores are only needed for days or weeks. Contractors who do this work regularly often own their own. The decision comes down to:
- How long the shores are needed. A beam installation might need them for a few days; a job waiting on inspections or a long lead time on steel needs them longer.
- How many and how tall. Rental stores stock a range of heights. Ceiling height, and whether the shores sit on the floor or on cribbing, decides which size you need.
- Load. If the design calls for heavy-duty shores or shoring towers, a formwork and shoring supplier is usually the source.
- Who is responsible. On a contracted job, the contractor normally supplies and sets the shoring as part of the work. If you're hiring someone, ask how they shore and who checks it.
Workers on construction projects in Ontario are covered by the province's construction regulation (O. Reg. 213/91 under the Occupational Health and Safety Act), so contractors have their own obligations for temporary supports on their sites.
Common shoring mistakes
- Too few shores. Spreading a wall's worth of load over two posts overloads both the posts and the floor they sit on.
- No top beam. A shore pushing on one joist leaves the next joist unsupported.
- Bearing on the slab without a check. A thin slab over loose fill can settle under a shore, so the floor above drops while everyone assumes it's supported.
- Removing shores too early. Shores stay until the permanent beam, posts and connections are complete and any grout or concrete under the posts has gained the strength the designer requires.
- Leaving temporary posts in. A rental shore or an unlabelled jack post isn't a permanent column. Permanent supports need to meet the code, as covered below.
When a temporary post becomes permanent
Once the work is done, the shores come out and the permanent structure carries the load. In a basement, that's usually a fixed steel column or an approved adjustable column on a proper footing.
Under Article 9.17.3.4 of the 2024 OBC, an adjustable steel column can be a permanent support if it conforms to CAN/CGSB-7.2, "Adjustable Steel Columns," and the load on it doesn't exceed 36 kN. Columns outside those limits are designed under Part 4. Our post on whether teleposts can be permanent explains how to read the label. If you're replacing a row of temporary or tired posts, how to replace lally columns walks through it.
Permanent steel posts made to length
We don't rent shoring equipment. What we do is fabricate the permanent supports that replace it: HSS steel posts with welded base and cap plates, drilled for anchors and beam connections, cut to the height on your drawings, along with the steel beams they carry. We supply and install basement beams and posts and deliver across the GTA and Ontario. Send us your drawings for a quote, or see the steel posts and beams we fabricate.
Frequently asked questions
Can you rent lally columns?
Not really. A lally column is a permanent steel column cut to length for one spot. What rental stores carry are adjustable steel shores and jack posts for temporary support. The permanent column is bought, fabricated or supplied by your contractor once the work is designed.
Where can I rent steel jack posts?
General tool-rental and equipment-rental outlets usually carry adjustable steel shores, and concrete formwork and shoring suppliers rent heavier post shores and shoring frames. Ask for the manufacturer's load table for the exact model you rent.
How much weight can a rented jack post hold?
It depends on the model and how far it is extended. Adjustable shores are rated by the manufacturer, and the rated load usually drops as the post is extended. Use the load table for that specific product and never assume a rating from a different model.
Can I leave a temporary jack post in permanently?
Only if it is a column approved for permanent use. In Ontario, an adjustable steel column can be permanent if it conforms to CAN/CGSB-7.2 and carries no more than 36 kN. Rental shores and unlabelled jack posts are temporary equipment and come out once the permanent structure is in.
