Sofa Sagging on One Side? Here's What's Happening and How to Fix It

Why Your Sofa Sags More on One Side

Asymmetric sagging almost always has one cause: uneven use. Most people have a preferred seat on their sofa — the same spot, every time. Over years, that specific area experiences far more compression than the rest. The cushion foam flattens faster, and the base webbing or springs under that spot lose tension faster than the rest.

The fix depends on whether the problem is in the cushion or the base.

Step 1: Diagnose the Problem

Remove all seat cushions. Press down firmly on the exposed base fabric in different spots. If one area feels noticeably softer or springier than the others, the base webbing or springs are unevenly worn — this is the structural cause. If the base feels even throughout, the problem is the cushion foam itself.

Fix for Uneven Base Webbing: Support Board

A sofa support board placed under all the cushions creates an even, firm surface across the entire sofa — including the heavily-used spot. This immediately compensates for the uneven base tension and restores level seating across the whole sofa.

The board distributes weight evenly regardless of where on the sofa you sit, which also prevents the lopsided problem from getting worse in the future.

Fix for Uneven Cushion Foam: Rotation and Replacement

If the base is even but one cushion is noticeably flatter than the others:

• Rotate cushions — swap the flat cushion to a less-used position, move a firmer cushion to the favourite seat
• Flip reversible cushions — if your cushions are double-sided, flip the worn side down
• Add foam topper — cut a piece of high-density foam to fit inside the worn cushion cover, restoring height and firmness

Preventing It in the Future

The most effective prevention: rotate cushions every 2–3 months. Swap positions left to right and flip reversible cushions. Combined with a support board that provides even base support, this keeps your sofa wearing evenly for years longer.