Can you lay concrete in the rain? - Explained By Converge

April 9, 2023

Have you ever wondered what would happen if it started raining right in the middle of pouring concrete? Would the whole process be interrupted or could fresh concrete survive the rain? Since the weather forecast is not always right a workday could easily be interrupted by a sudden downpour. 

For people who work in areas with a high number of rainy days, this is a problem they have to deal with on a weekly basis. People in these areas would not get much done if they had to stop working every time it rained. Keep reading to find out:

1. How rain affects concrete

2. Does and don’ts for concreting in the rain

3. The answer to the question “Can you lay concrete in the rain?”

Read more: What happens if concrete freezes and how do you measure concrete temperature?

Can you pour concrete in the rain?

Surprisingly, yes, it is possible to pour concrete in the rain. However, it requires some precautions in order to make sure that you will still get the best result possible. It is good to always be prepared for rain and to keep an eye on the weather forecast when planning a big job.

Having the tools to protect the concrete from rain will save you from having to redo the surface due to water damage. Read more about what precautions to take to protect concrete from rain in our article. If you can’t protect the concrete from heavy rain it would probably be better to postpone the job until the rain has passed. 

The effects of rain on concrete

Concrete is made up of a mix of cement, aggregates and water. The ratio of these three ingredients are important in order to create a chemical reaction which hardens and strengthens the concrete. If the ratio is off due to heavy rain adding too much water into the mixture, the concrete will be weakened. 

The effects of rain on concrete will differ depending on how much time has passed since pouring the concrete. Below we explain how rain affects concrete in various stages of curing.

Immediately after pouring

If it were to start raining right after pouring the concrete it can cause damage to the surface. What happens when the rain hits the fresh concrete is that the rain washes the cement out of the concrete. This applies to the concrete closest to the surface. 

When the cement washes out it can lead to issues such as:

  1. Surface scaling
  2. Dusting
  3. Craze cracking

After 4- 8 hours

Is the forecast showing that it is going to rain a few hours after you finished pouring the concrete? Then you can probably relax. Approximately 4-8 hours after finishing the pouring process the concrete mixture will start to stiffen up. This means that rain on concrete after 8 hours most likely won’t cause any significant damage.

After 24 hours

Rain 24 hours after finishing laying concrete should not be a problem. The concrete is almost fully dry by that point and will not be affected by rain. A little bit of rain might even be good for the curing process. 

Read more: Read up on concreting in hot weather and concreting under water.

Person stands next to a puddle on concrete

Do’s and don’ts for pouring concrete in the rain

There are important things to consider before pouring concrete in the rain. Therefore we have gathered the most important do’s and don’ts for concreting in the rain. 

Do’s

  • DO check the weather forecast so you can make any necessary preparations in advance.
  • DO reschedule if it is possible. Especially if a lot of rain is expected.
  • DO push the rainwater off the edge of the concrete once the rain passes.
  • DO cover up the worksite if you expect rain shortly after finishing the pouring process.
  • DO check back over time to keep removing rainwater.

Don’ts

  • DON’T forget to assess the situation once the rain passes. Look over any potential damages and figure out a solution.
  • DON’T consciously push the rainwater into the fresh concrete mix while it cures. 
  • DON’T pour concrete into cavities that are already filled with water. It will change the ratio of the mix and compromise the strength.
  • DON’T add more cement to the wet concrete to soak up rainwater after you have finished pouring the concrete. 

Frequently asked questions

What is the best weather to pour concrete?

There are many aspects to consider when determining the best weather to pour concrete. Some of them are temperature, humidity etc. Learn more about what weather is the most optimal for pouring concrete in our article.

What happens if you don’t water concrete?

If the concrete dries out before the concrete has reached it’s full possible strength the curing process will stop. This means that the concrete will not continue to gain more strength. 

Will concrete with too much water cure?

Yes, the concrete will cure despite too much water. However, too much water means that there will be excess water trapped inside the concrete once it is fully cured. This will lead to cracks which will reduce the strength of the concrete. 

Read more: Learn about long term effects of hot climates and cold climates on concrete and how to pour concrete in freezing conditions.

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