Time for Formwork Removal in Prefabricated Houses

The time for formwork removal in prefabricated houses varies significantly depending on factors such as the type of component, season, and curing conditions, and needs to be discussed on a case-by-case basis:

I. Classification by Component Type

1. Side Formwork: It can usually be removed within 1-5 days. After pouring concrete on the second floor in summer, the side formwork can be removed within 1-2 days; side formwork for columns or walls requires 3-5 days, but after removal, it should be promptly wrapped with a curing membrane to prevent cracking due to moisture loss. The removal of side formwork requires that the concrete strength be ≥1.2MPa to ensure no surface damage.
2. Bottom Formwork:
   • Summer (above 25℃): The bottom formwork for floor slabs or beams (with a span ≤8m) requires 10-14 days; after pouring concrete on the second floor, it requires 18-20 days.
   • Winter (below 5℃): It needs to be extended to 14-21 days, and thermal insulation measures (such as covering with cotton quilts or electric blankets) should be taken to avoid slow strength growth due to low temperatures.
   • Specification Requirements: When removing the bottom formwork for slabs/beams with a span ≤8m, the concrete strength should reach ≥75% of the design strength; the bottom formwork for cantilever components (such as balconies and awnings) should reach 100% of the design strength.
3. Other Components: Prestressed components (such as prestressed beams and slabs) require the concrete strength to be ≥100% of the design value, usually taking 21-28 days.

II. Influence of Season and Curing Conditions

1. Spring and Autumn: The specific time is not clearly defined, but since premature formwork removal in winter is prone to cracking, it can be inferred that the formwork removal time in spring and autumn is between that of summer and winter, and should be determined in combination with on-site test block strength reports.
2. Curing Conditions: When the humidity is below 60%, water spraying curing is required; otherwise, the concrete is prone to cracking, and the formwork removal time should be delayed. Adding water reducers or accelerators can speed up the process by 20%-30%. Early-strength cement can shorten the time to 3-5 days, while slag cement takes longer.

III. Key Precautions
In actual projects, the laboratory test block strength report should be used as the basis to avoid structural deformation or cracking due to premature formwork removal. For example, in winter, even if the theoretical number of days is reached, the concrete strength may still be insufficient if no thermal insulation measures are taken. In addition, the formwork removal sequence should follow the principle of "first erected, last removed; last erected, first removed" to ensure structural safety.