SPC Flooring Blisters And Bubbles With Water Inside Causes And Fix

SPC Flooring Blisters and Bubbles With Water Inside Causes and Fix 2024

SPC flooring is waterproof at the plank level. But sometimes after installation, bubbles or blisters appear on the surface. When you press on them, they feel soft and may contain moisture underneath. This is almost never a product defect. It is a subfloor moisture problem.

Why Blisters Form

SPC is installed as a floating floor. The planks lock together but the floor is not sealed to the subfloor. If moisture comes up from the concrete slab, it gets trapped between the subfloor and the SPC backing. The moisture has nowhere to escape. It collects in low spots under the flooring. Over time, the pressure pushes up on the SPC planks and creates visible bubbles.

Subfloor Moisture Is the Number One Cause

The most common cause is concrete that has not fully cured before installation. New concrete takes 30 to 60 days to reach a moisture level safe for flooring. If SPC is installed too early, the moisture from the concrete rises and gets trapped.

Another cause is slab-on-grade construction without a proper vapor barrier under the concrete. Ground moisture travels through the concrete slab and reaches the flooring. Even if the surface of the concrete feels dry, moisture can still migrate through.

The third cause is water leaks. A slow leak from a pipe or a plumbing fixture can saturate the subfloor in one area. The moisture travels under the SPC and creates a blister far from the leak source.

Is EPE Enough to Stop Moisture

Many installers lay EPE foam under SPC flooring thinking it protects against moisture. Standard EPE has some moisture resistance but it is not a vapor barrier. EPE is a closed cell foam in theory, but low quality EPE contains open cells that absorb and hold moisture like a sponge. When EPE gets wet, it holds the moisture against the SPC backing and makes the problem worse.

The correct approach is to install a dedicated vapor barrier of at least 0.15mm polyethylene film with taped seams, then lay the underlayment on top. The vapor barrier stops moisture from reaching the flooring. The underlayment provides comfort and sound reduction.

Temperature Related Blisters

In some cases the blister is not water but air trapped by temperature changes. If a large room has SPC installed without enough expansion gap, temperature changes cause the floor to expand. The pressure can create bubbles at weak points. These air blisters are usually temporary and disappear when the temperature stabilizes.

How to Fix

Small blisters with visible moisture require removing the affected planks. Dry the subfloor thoroughly. Install a proper vapor barrier. Reinstall the planks or replace them if damaged. Large areas with multiple blisters suggest a systemic moisture problem. The entire floor may need to be removed, the subfloor dried and treated, and new flooring installed with proper vapor barrier.

For air blisters from temperature changes, check the expansion gaps around the room perimeter. If gaps are too small, remove baseboard and trim the planks to create proper space. The bubbles should flatten within a few days after the floor has room to move.

Prevention

Test concrete moisture before installation using a moisture meter or calcium chloride test. The reading should be below 4 percent for most SPC products. Wait at least 30 days after concrete is poured before installing flooring. Install a polyethylene vapor barrier over concrete subfloors regardless of whether the concrete looks dry. Use the correct underlayment thickness for SPC, not thicker than 2mm.

About PROLEADER

PROLEADER SPC flooring is dimensionally stable and waterproof at the plank level. Blisters caused by subfloor moisture are not a product defect. Contact us for installation guidelines and subfloor preparation recommendations.