Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Rained hard right after concrete pouring

Rained hard right after concrete pouring

Rained hard right after concrete pouring


I am building a house, and yesterday the contractor poured concrete on the 2nd floor slab. Just about 5-10 minutes after the process was completed, it rained very hard for around 30 minutes. The areas were not covered on time, and some of slabs were soaked with water. I want to ask this:

According to the contractor, as long as the pouring is finished, it is okay if it rains because water will not penetrate the concrete as long as it doesn't happen during the process. Is this true? Because I saw water on top of the concrete, but there is no way to find out if it never penetrated the concrete.

So is it true that it is okay to rain right after (just 5 mins after pouring it rained) pouring, and that it won't penetrate the concrete?

Will this compromise the strength of the structure esp since this is a 2nd floor?


RE: Rained hard right after concrete pouring

In that it is good, in general, to keep concrete wet while it is curing, if should not hurt the strength.

However, did this not ruin any smooth finish that was there prior to the rain?  Or does that matter?  

Mike McCann
MMC Engineering


RE: Rained hard right after concrete pouring

I am aware that it is good to keep concrete good, but is it the same if it rains rain after the pouring when the concrete is not yet dry? Contractor claims it is okay, because it won't penetrate concrete.

Smooth finish wiped off some of the surface. And when the men covered the area, they stepped on the concrete thus leaving footmarks. When the rain subsided, they removed the covered, and leveled the surface so the footmarks will be wiped away

RE: Rained hard right after concrete pouring

With a relatively mild rain, when concrete is rained on, it usually ends up with a 'sandy' type of finish.  The cement is washed away leaving a 'pebbled' type of surface with loose sand on the surface.

Has the surface been damaged? and can you post a photo?


RE: Rained hard right after concrete pouring

Excess water on the concrete surface.  Maybe good - Maybe bad.

If the excess water is not worked into the concrete, probably no harm done to the concrete mass.
The flushed surface is a fault and that may be what the final dispute will be over.

RE: Rained hard right after concrete pouring

If the concrete has been finished, the rain will not hurt it.  If the concrete had not been finished (floating, troweling, etc.) then you can have some durability issues, mostly in the form of "map" cracking and dusting/scaling.

RE: Rained hard right after concrete pouring

Agree with Ron but you can have water on the surface before finishing as long as you let it evaporate before finishing takes place. This is common in severe situations where rate of evaporation is greater than the concrete bleed rate (Silica Fume mixes come to mind)and fogging is required. What you want to avoid is diluting(weakening)the surface paste. Timing is everything!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close