(+220) 385-7732
We rent adjustable steel props, also called acro jacks, at D4 each per day. They extend up to 4.5 metres. Most people know how many props they need. What catches them out is how many days. A small floor slab needs props for about 4 days. A wide beam can need 21. Tell us the span and we will work the days out with you.
Props hold up the wet concrete until the concrete is strong enough to hold itself up. Simple job. The only question is how long that takes.
What we rent
| What it is | Adjustable steel prop (acro jack) |
| How high it goes | Up to 4.5 metres |
| Price | D4 each, per day |
| Where to collect | Lamin Daranka · Jabang · Yarambamba ( OIC Road ) · Bijilo ( OIC Road ) · Jambanjelly |
More detail on the acro jacks page. All our prices are on the price list.
How many days will you need them?
This depends on one thing: how far the concrete has to reach between its supports. That distance is called the span.
A short span is easy for the concrete. It can carry itself sooner, so the props come out sooner. A long span is harder. The concrete needs more time to get strong enough, so the props stay up longer.
The American Concrete Institute publishes the days. This is their table, in plain terms.1
| What you are propping | How far it spans | Days before it all comes off |
|---|---|---|
| A floor slab | Less than 3 m | 4 days |
| A floor slab | 3 to 6 m | 7 days |
| A floor slab | More than 6 m | 10 days |
| A beam | Less than 3 m | 7 days |
| A beam | 3 to 6 m | 14 days |
| A beam | More than 6 m | 21 days |
Notice beams need roughly twice as long as slabs. That is why we ask what you are propping, not just how big the job is.
A worked example
Say you are propping a floor slab in a room 4 metres across. Look up the table:
- It is a floor slab, so use the slab rows.
- It spans 4 metres, which falls in the 3 to 6 m row.
- So the props stay up 7 days.
Now put your own prop count against that. If your design calls for 60 props, it is 60 × D4 × 7 days = D1,680. If it calls for 100, it is D2,800.
Now the same room, but propping a beam instead of a slab. Same span, but beams take 14 days, so the same order costs twice as much. Nothing changed except what you are holding up.
Two more things about the table. ACI also lists a shorter set of days for some jobs, and your engineer decides whether those apply to yours — the days above are the more cautious set. And ACI counts days where the air stays above 10°C.1 That is every day here, so you just count normal days.
The real rule is about strength, not days
Those day counts are a fallback, for when nobody has tested the concrete. The actual rule ACI gives is this:1
Supporting forms and shores should not be removed from beams, floors, and walls until these structural units are strong enough to carry their own weight and any approved superimposed load.
In plain terms: leave the props until the concrete can hold up itself plus whatever is going on top of it.
ACI also says who makes that call. It should be specified by the engineer or architect, not decided on site.1 So if your engineer gives you a number, use theirs.
If you are building a floor above
When you pour the next floor before the one below has fully hardened, the lower floor takes weight it is not ready for. The fix is to put props back underneath it. That is called reshoring.
It means a second set of props, on top of the ones you already planned. ACI says these should go back in the same day the forms come off, and that an engineer should decide how many and where they go.1
So if you are going up a floor, tell us. It changes the number of props, not just the days.
What to tell us when you order
- Whether you are propping a slab or a beam.
- The span — how far it reaches between supports.
- The height from the floor up to the underside of the concrete, so we know the props will reach.
- Whether you are building a floor above it later.
That is enough for us to tell you how many props and how many days. WhatsApp (+220) 385-7732.
And if you run short partway through, call us rather than taking props out early. At D4 a day, adding more is the cheaper mistake.
Common questions
- How much does it cost to rent acro jacks in The Gambia?
- D4 each per day from GLS Rental. The props are adjustable steel and extend up to 4.5 metres. You can collect from Lamin Daranka, Jabang, Yarambamba ( OIC Road ), Bijilo ( OIC Road ) or Jambanjelly.
- How many days do props stay under a slab?
- It depends on the span, meaning how far the concrete reaches between supports. The American Concrete Institute lists 4 days for a floor slab spanning less than 3 m, 7 days for 3 to 6 m, and 10 days for more than 6 m. Beams take longer: 7, 14 and 21 days for those same spans.
- What is a span?
- The distance the concrete has to reach between its supports. A shorter span is easier for the concrete to carry, so props can come out sooner. A longer span needs more time.
- Why do beams need props for longer than slabs?
- A beam carries more concentrated weight than a floor slab, so it needs to reach a higher strength before it can support itself. In the ACI 347-04 figures, beams need roughly twice as many days as a slab of the same span.
- What is reshoring?
- Putting props back under a floor after the forms have come off, so that floor can help carry the weight of the next floor being poured above it. ACI 347-04 says reshores should go back the same day the forms are removed, and that an engineer should decide how many and where. It means renting extra props beyond your original count.
- How high do your acro jacks extend?
- Up to 4.5 metres. They adjust with a pin for the rough height and a thread for fine adjustment.
Sources
Every technical figure above comes from one of these. We quote and summarise them; we do not add guidance of our own.
1. American Concrete Institute, Guide to Formwork for Concrete (ACI 347-04)
Cited for: The number of days props stay up by span, the half-time note for stripping moulds without disturbing the props, the strength rule behind those days, who decides when props come out, the 10°C condition, and reshoring (sections 3.7 and 3.8).
Tell us what you are building
Send your dates and a photo of the site or the drawing. We will work out what you need and what it costs.