Rain matters because freshly poured concrete is particularly sensitive to excess water. If rainwater mixes into the concrete before it has had a chance to set, it can weaken the structure, damage the surface finish, and throw off the water-cement ratio. That’s why it’s crucial to avoid pouring onto waterlogged ground or into trenches where water has pooled. If the concrete pushes water to the surface, it can create puddles that compromise the top layer.
Timing is everything. In the first two hours after pouring, concrete is at its most vulnerable. If rain is forecast during this window, it’s best to delay the pour or have protective covers ready. Between two and four hours in, the concrete begins to set, but it still needs shielding from rain. After four hours, it’s usually firm enough to walk on, and light rain is less of a concern. Once eight hours have passed, the risk of damage drops significantly, though it’s still wise to keep the surface protected as it continues to cure over the next few days.
To protect your pour, always check the local forecast for Brentford or Wembley before starting. If rain is likely, prepare waterproof sheeting or tarpaulins in advance. During the pour, use these covers to shield the area, especially if you’re working on a large slab. Temporary shelters made from timber and tarps can also be effective. After the pour, keep the concrete covered for at least four to eight hours to allow it to set properly. Make sure water can drain away from the surface to prevent pooling.
There are a few key things to keep in mind. Never try to soak up rainwater with dry cement—it might seem like a quick fix, but it weakens the mix. Don’t work rainwater into the surface either, as this can ruin the finish. And always pour onto dry, stable ground to give your concrete the best start.
If you’re working on a site in Brentford, Wembley, or nearby, and you’re unsure whether to go ahead with a pour, or need advice on how to protect your site, just give us a call. Our team at Procon Readymix is here to help you get the job done right—rain or shine.