When to Pull Forms from Concrete in Construction: A Complete Guide
In concrete construction, formwork acts as a temporary mold that supports fresh concrete until it gains enough strength to bear its own load and retain its shape. Once the concrete has sufficiently hardened, these forms must be removed—but when exactly should you pull the forms from concrete?
Removing the forms too early can weaken the structure, while removing them too late may cause project delays and increased costs. This article explains when to pull forms from concrete, what factors affect timing, recommended timelines, strength requirements, and safety practices to follow on the job site.
What Does “Pulling Forms” Mean in Construction?
“Pulling forms” refers to the process of removing the temporary molds (wood, steel, aluminum, or plastic) used to hold freshly poured concrete in place. These forms support various components like walls, columns, beams, slabs, stairs, and footings.
Once the concrete sets and gains sufficient strength, the forms are carefully pulled or stripped to expose the hardened concrete structure.
Why Proper Timing Is Crucial
Concrete is a hydration-based material that slowly gains strength over time. Pulling the forms too soon—before enough strength develops—can lead to:
- Surface cracking
- Structural deformation
- Sagging or collapse
- Increased repair costs
On the other hand, waiting too long can result in:
- Construction delays
- Difficulty removing the forms
- Increased labor costs
- Staining or bonding issues from prolonged form contact
Conclusion: Timing must be precise, and based on concrete strength—not just time elapsed.
Key Factors That Influence Form Removal Timing
Several variables affect how soon forms can be pulled from a concrete structure:
1. Concrete Mix Design
- High early-strength mixes allow earlier form removal.
- Retarded mixes or additives may require more time.
2. Curing Temperature
- Warmer temperatures accelerate curing.
- Cold weather slows down hydration and delays form removal.
3. Structure Type
- Vertical structures (walls, columns) can have side forms removed earlier.
- Horizontal load-bearing structures (slabs, beams) require more strength before removal.
4. Concrete Strength Achievement
- Strength is the primary determinant.
- Forms should be removed when concrete reaches 500–700 psi for vertical forms and 70–100% of design strength for load-bearing parts.
5. Formwork Material
- Steel and aluminum forms dissipate heat faster and may allow earlier stripping.
- Wood forms insulate and may retain moisture longer, slowing strength gain slightly.
General Guidelines: When to Pull Forms from Concrete
Here’s a practical overview of recommended times to pull forms in standard curing conditions (20°C or 68°F) with regular Portland cement.
| Concrete Element | Form Removal Time | Strength Required | Notes |
|---|---|---|---|
| Vertical Walls & Columns | 24–48 hours | ~500–700 psi | Non-load bearing sides only |
| Slab Edges (Side Forms) | 3–4 days | Not critical if edges only | Bottom supports remain |
| Beam and Slab Bottom Forms | 7–14 days | 70–100% of design strength | Support props may stay longer |
| Footings | 1–2 days | ~500 psi | Safe if no immediate load |
| Stairs (Structural) | 3–7 days | 70–100% of design strength | Timing depends on stair span and use |
These are general guidelines. Always verify with the structural engineer and strength testing results.
How to Know If It’s Safe to Pull Forms
✅ Rely on Concrete Strength, Not Just Time
Concrete should be tested or estimated to reach certain strength thresholds before pulling the forms:
| Element Type | Strength Needed Before Removal |
|---|---|
| Vertical Walls | 500–700 psi |
| Slabs (with traffic) | 70–100% of design strength |
| Beams and Girders | 75–100% of design strength |
| Footings | ~500 psi |
✅ Testing Methods
- Compression Testing (ASTM C39): Tests strength on concrete cylinders.
- Concrete Maturity Method: Estimates strength based on temperature and curing time.
- Rebound Hammer Test: Non-destructive estimate of surface hardness and strength.
Best Practices for Pulling Concrete Forms
Following proper techniques ensures that pulling forms doesn’t damage the newly set concrete:
✅ Use the Right Tools
- Pry bars, hammers, wedges, and lifting hooks
- Avoid striking the concrete directly
- Remove nails, ties, or clamps gently
✅ Start with Non-Critical Forms
- Begin with non-load-bearing sides
- Save soffits, bottom forms, and structural props for later
✅ Support Load-Bearing Elements
- Keep props under slabs and beams until full strength is achieved
✅ Continue Curing After Form Removal
Concrete gains strength up to 28 days. Use curing methods like:
- Wet burlap
- Curing compounds
- Plastic sheeting
- Water misting
✅ Inspect Concrete Before and After Form Removal
Check for cracks, discoloration, or defects. If issues are found, consult with a structural engineer before proceeding.
Environmental Considerations
| Weather Condition | Effect on Form Removal |
|---|---|
| Cold Weather (<10°C) | Slows curing; extend removal time by 1–2 days |
| Hot Weather (>30°C) | Accelerates curing; monitor moisture levels |
| Rain/Humidity | May delay formwork drying; risk of staining |
| Windy Conditions | Speeds up surface drying; risk of cracks |
Summary Table: When to Pull Concrete Forms
| Structure Type | Safe Removal Time | Strength Required |
|---|---|---|
| Walls and Columns | 1–2 days | 500–700 psi |
| Slab Edges | 3–4 days | Edges only |
| Beam Bottom Forms | 7–14 days | 75–100% of design strength |
| Foundation Footings | 1–2 days | 500 psi |
| Stairs (Structural) | 3–7 days | 70–100% of design strength |
Mistakes to Avoid When Pulling Concrete Forms
- Removing too early
- Risk: Sagging, cracking, or failure
- Using excessive force
- Risk: Surface spalling or edge chipping
- Ignoring strength testing
- Risk: Failure under load
- Delaying form removal unnecessarily
- Risk: Wasted labor and potential discoloration or bonding issues
- Skipping curing after removal
- Risk: Incomplete hydration and long-term weakness
Construction Standards for Form Removal
- ACI 347R-14: Guide to Formwork for Concrete
- ASTM C31, C39: Field curing and compressive strength testing
- OSHA 1926 Subpart Q: Safety during concrete and masonry construction
These codes help ensure quality construction and worker safety during formwork operations.
Conclusion
Knowing when to pull forms from concrete is a balance between safety, structural integrity, and construction efficiency. While time-based estimates provide a helpful guide, the actual strength of the concrete should dictate form removal decisions.
By combining proper testing, curing, and field observation, you can ensure that the forms are removed safely and at the optimal time, paving the way for a solid and long-lasting structure.
FAQs: When to Pull Forms from Concrete in Construction
1. Can I pull forms after 24 hours?
Yes, but only for vertical sides like wall or column forms—not for slabs or beams. Ensure the concrete has reached ~500 psi.
2. How long should slab forms stay in place?
Side forms can be pulled in 3–4 days. Bottom forms and props should stay for 7–14 days or until strength reaches 70–100% of design value.
3. What is the minimum strength needed to pull forms?
Around 500–700 psi for vertical elements; 70–100% of design strength for slabs, beams, and other structural components.
4. Does weather affect when I can remove forms?
Yes. Cold weather slows curing, requiring more time. Hot weather speeds up curing but increases the risk of surface cracks.
5. What happens if I pull forms too early?
The concrete can crack, slump, or collapse, especially in load-bearing elements.
6. Should I cure concrete after removing forms?
Yes. Curing must continue to allow concrete to reach full strength (usually over 28 days).
7. Can I reuse formwork after pulling it?
Absolutely. Steel, aluminum, and high-quality wood forms can be reused multiple times if undamaged.
8. Who decides when forms should be removed?
Typically, the site engineer, project manager, or foreman, based on strength tests and project specifications.
9. Is strength testing mandatory before pulling forms?
For structural elements, yes. It’s best practice to verify strength using compression or maturity methods.
10. Do different types of concrete affect form removal timing?
Yes. Fast-setting or high-early-strength concrete allows earlier form removal compared to standard mixes.
