Tips for Pouring Concrete in the Rain

Weather delays are an unavoidable part of commercial construction, especially across Alberta, where fast-moving systems can turn a clear morning into a wet jobsite. At Dynamic Concrete Pumping, Inc., we’ve spent more than 40 years helping commercial contractors navigate these challenges with dependable pumping, placing, superflat flooring and finishing services throughout Calgary, Edmonton and the surrounding regions. We understand the pressure to keep projects moving, even when conditions aren’t ideal.

Here, we’ve put together our best tips for pouring concrete in the rain, so you can protect fresh material throughout the curing process and keep your projects moving forward.

Can You Pour Concrete in the Rain?

Yes, but you need the right preparation and protection.

Rain does not automatically ruin a concrete pour, but it can compromise surface strength, cause scaling, disrupt finishing and dilute the mix if crews don’t respond quickly. For contractors across Alberta and Western Canada, the key is knowing how to pour concrete in the rain while maintaining compliance with Canadian construction standards and best-practice guidelines.

How to Pour Concrete in the Rain

These tips for pouring concrete in the rain apply to a wide range of commercial pours, from industrial slabs to parking structures and more:

Prepare the Site With Rain-Ready Protection

Before beginning your pour, crews should have tarps, Visqueen sheets or temporary canopies staged and ready for fast deployment. Alberta weather can shift quickly, and having these materials in place allows teams to shield the placement area without disrupting workflow.

Ensure Proper Subgrade Drainage

Standing water on the subbase can reduce slab performance and impact load-bearing capability. If rain is in the forecast, crews should verify that the subgrade is compacted, stable and properly drained. Pumping out shallow water or lightly regrading certain areas may be necessary before placement.

Don’t Allow Rainwater to Dilute the Mix

Rain that falls directly onto the concrete during placement can alter the water-cement ratio. To prevent this, use covers strategically, minimize exposure during highly vulnerable phases, such as the initial set, and coordinate closely with your pumping provider to maintain a steady workflow.

Avoid Finishing While Water Is on the Surface

One of the most important rules when laying concrete in the rain is to avoid troweling standing water into the slab. This weakens the surface layer, leading to dusting, flaking, spalling and other issues later on.

If light rain does occur, let the water evaporate naturally once the rain stops, or gently remove the water without disturbing the surface. Only resume finishing when the concrete has reached proper stiffness and the surface is free of excess moisture.

Use Appropriate Admixtures When Needed

Some commercial mixes include accelerators or water-reducing admixtures that help maintain performance during cold and damp weather. Work with your supplier to ensure the mix design suits the project conditions, especially for large-scale structural placements.

Maintain Communication Across the Crew

Rain-affected pours require tight coordination between pump operators, finishers, supervisors and laborers. Always check weather forecasts before pouring, and prepare to cancel a pour if heavy rain is predicted.

Protecting Concrete From Rain During Curing

Even once the concrete is placed, the job isn’t done. Protecting concrete from rain during early curing is essential because excessive moisture can:

• Mark or erode the surface.
• Disrupt hydration.
• Cause scaling, delamination or uneven hardening.
• Compromise surface tolerances on superflat floors.

Here’s how to safeguard your slab:

• Keep protective covers in place during the initial cure: Curing begins immediately after finishing. If rain continues or returns, covers should remain in place without touching the concrete surface. Lightweight frames or suspended coverings can prevent the material from imprinting onto the slab.
• Prevent runoff from washing across the slab: Redirect downspouts or set up barriers so rainwater does not channel across freshly placed concrete. Even minor runoff can leave blemishes or affect curing uniformity, especially on industrial floors requiring precision flatness.
• Watch for puddles: If you’re using a tarp or another surface, pooling water can weigh your tarp down and cause contact with the surface of the concrete. Prevent this by placing your tarp or other structure in a way that prevents puddles. Watch for any water accumulation on the surface and remove it before it can cause damage.
• Allow the concrete to stabilize before removing coverings: Concrete should cure for at least 24-48 hours before any additional moisture is introduced and before any foot traffic is allowed. Once the concrete has reached its initial set and the surface is firm, coverings can be lifted carefully to check for moisture issues. Crews should evaluate whether patching or reworking is necessary before proceeding with later-stage finishing, cutting or polishing.

What to Do After Pouring Concrete in the Rain

Even with careful planning, unexpected rain may still hit during or right after a pour. Here’s what to do when you’re caught in the rain during a pour:

• Try to cover the surface quickly: You should have tarps or other structures that allow you to move fast to protect the surface.
• Assess the surface once the rain stops: Crews should evaluate surface texture, water accumulation and potential washout. Also, look for a weak, milky layer, which can be a sign of laitance. If necessary, weak surface material can sometimes be removed and reworked before the slab fully hardens.
• Reschedule finishing as needed: When rain interrupts the finishing window, teams may need to delay troweling or follow modified finishing protocols. Rushing this stage can damage the slab, so waiting for the right stiffness is crucial.
• Plan for follow-up grinding or polishing if required: On some commercial floors, a light grind or polish may correct minor surface changes caused by unexpected moisture.
• Monitor curing: Rain can extend curing times. Extended protection or delayed loading can help ensure the concrete’s long-term performance.

Why Contractors Trust Dynamic Concrete Pumping

Rain, cold snaps and weather variability are part of building in Western Canada. With the right strategies, crews can still achieve dependable results, and working with Dynamic Concrete Pumping can make all the difference.

Our investment in modern technology and commitment to jobsite efficiency help contractors deliver outstanding results, even in challenging weather. If you need pumping, placing, superflat finishing, Soff-Cut, grinding or polishing services, request a quote today.