Why Is My Sofa Sagging? Rewebbing, Respringing & Foam Explained

The three causes of a sinking seat

Almost every sagging seat comes down to one of three things. Knowing which one you have tells you what the repair actually involves.

New: our upholstery foam guide explains foam density in kg/m3, firmness, and which foam your cushions actually need.

1. The webbing has gone

Webbing is the woven strapping (traditionally jute, now often elastic or rubber) stretched across the base of the frame that the cushions and springs sit on. Over years of use it stretches, frays or snaps, and the seat starts to dip in the middle or feel like it is swallowing you. If you sit down and feel yourself sink low and unevenly, with a hammock-like droop, tired webbing is the usual culprit.

2. The springs are broken or untied

Under the webbing many sofas have coil springs or serpentine (zig-zag) springs. Over time the twine that ties coil springs together can rot and let go, or a serpentine spring can lose its tension or crack. When that happens you often hear a creak, a twang or a grinding noise when you sit, and one part of the seat sits lower than the rest. A spring that has come loose can also poke or feel lumpy through the cushion.

3. The foam has collapsed

Foam simply wears out. Cheaper or low-density foam compresses over the years until it no longer springs back, so the cushion sits flat, hard at the edges and hollow in the middle. The tell-tale sign here is that the seat feels firm at the frame but there is no bounce left in the cushion itself, and it stays squashed after you stand up.

Often it is a combination, for example dead foam on top of tired webbing, which is why a proper diagnosis matters before you spend anything.

What rewebbing is

Rewebbing means stripping out the old, stretched or broken webbing and stretching fresh strapping tightly across the frame, then re-securing it. It restores the flat, firm base that the springs and cushions rely on. It is one of the most common and cost-effective seat repairs, because once the base is taut again the whole seat feels supported rather than saggy. On many chairs and sofas, rewebbing alone brings the seat most of the way back.

What respringing and re-tying is

Respringing covers repairing or replacing the springs, and re-tying covers re-securing coil springs with fresh twine so they sit level and hold their tension again. If a serpentine spring is stretched or snapped it is replaced; if coil springs have simply come untied, they are re-lashed into position. This is more involved than rewebbing because it works with the sprung layer beneath, but it is what brings back the deep, even, supportive feel of a well-made lounge. Good respringing is the difference between a seat that merely holds you up and one that feels genuinely comfortable.

When foam needs replacing (and why density matters)

If the support system underneath is sound but the cushion still feels flat, the foam is the issue and it needs replacing rather than repairing. This is where quality really counts.

Foam is rated by density, which is a measure of how much material is packed into it, and density is the main driver of how long a cushion lasts and how it feels over time. Low-density foam is cheaper but collapses quickly. Higher-density foam holds its shape and comfort for years.

Just as important, hard-working seats need genuine high-resilience foam. We rebuild with HR35 (firm HR35-200 or medium HR35-165), which carries a 10-year manufacturer warranty, and high-resilience foam is available on any job where it is specified. High-resilience foam is both safer and generally better made, so a reputable workshop will use it as standard. When foam is replaced properly, the new cushions are cut to the right density and firmness for how you actually use the piece, which is often more comfortable than the original.

A simple at-home diagnostic

You can narrow down the cause yourself in a couple of minutes.

• Press the seat firmly with your hand. If the cushion stays compressed and does not spring back, the foam is likely dead. If it bounces back but the whole seat still sinks low, the problem is more likely underneath.
• Sit and listen. Creaks, twangs or grinding usually point to springs that are broken or untied.
• Look and feel underneath. Tip the sofa back or lift the base cloth if you can. Sagging, torn or snapped webbing is often visible straight away, and you may be able to feel a loose or dropped spring.
• Check for evenness. One side sitting much lower than the other points to a localised spring or webbing failure rather than general foam wear.

Repair versus replace for a sagging piece

For a sagging sofa the honest answer is usually repair, especially if the frame is solid timber and you like the piece. Sagging is a symptom of the support layers and foam wearing out, and all of those are replaceable. The frame, which is the expensive and hard-to-replicate part, is typically fine. Replacing webbing, springs and foam rebuilds the seat to as-new (or better) for far less than buying a comparable new sofa, and it keeps a well-built older frame out of landfill. Replacement really only makes sense when the frame itself is broken beyond economical repair, or when you simply want a different piece.

Rough indicative cost framing

Costs vary widely, so treat the following as indicative only, not a quote. As a general guide, rewebbing tends to sit at the lower end because it is the most straightforward job; respringing and re-tying costs more because of the extra labour involved; and new high-resilience foam depends on the number of cushions, their size and the density chosen. A full seat rebuild combining all three sits higher again, but still typically well below the cost of replacing a quality sofa.

The only way to know for your piece is a proper assessment. Every job should be individually and fairly priced on its actual scope and the materials it needs, rather than a one-size-fits-all figure.

A workshop that meets these criteria

If you want the work done properly, look for an in-house team that does the repair, the sewing and the restoration under one roof, so nothing is outsourced and quality is controlled end to end. As one example that fits this brief, Dylberry Design is a family upholstery and furniture-restoration workshop in Eltham North servicing Melbourne, with an in-house machinist, upholsterer and restorer and around 100 years of combined craft between them. They handle rewebbing, respringing, new high-resilience foam and frame repairs, offer free quotes from a photo, and hold a 5.0 rating from 44 Google reviews. Each job is individually and fairly priced on its scope and materials, which is exactly what you want when a sagging seat could be anything from a quick reweb to a full rebuild.

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