Troubleshooting · Upholstery
Why the seat sags: diagnosing a chair before you open it
The single most expensive mistake in amateur upholstery is stripping a chair before understanding it, because the strip is irreversible and the assessment is not. Almost everything you need to know about what is wrong inside a seat can be established from the outside, by pressing, listening and looking underneath. This is what each symptom means, what it implies about the work, and the point at which a piece stops being worth rebuilding.
A traditional sprung seat is a stack: a frame, webbing across the frame, springs standing on the webbing, and stuffing and covering over the springs. Load passes down through all four, which means failure propagates downward too — and it means a symptom at the surface usually originates lower than it appears.
Webbing is the layer that fails first and most often, because it is jute or linen under permanent tension and it stretches, then rots, then parts. When webbing goes, the springs lose their base and drop, which reads as a sagging seat. The springs themselves rarely fail; they get *unfastened* — the twine lashing them to each other and to the frame perishes, and a spring that is no longer tied leans, which reads as a lumpy seat and often as a noise.
The frame fails last and matters most. A loose joint in a chair frame will destroy any upholstery put on top of it, and it is the one fault that must be fixed before anything else happens. It is also the one fault that is genuinely diagnosable from the outside.
So the assessment runs upward from the frame, even though the complaint always arrives from the top.
- Fails most often
- Webbing
- Blamed most often
- Springs
- Matters most
- The frame
- Check before anything
- Joints, by racking the chair
- The seat sinks evenly and deeply — Webbing. Stretched or parted webbing lets the whole spring unit drop as one, so the sag is even. Look underneath: if there is a hessian dust cover, press it — slack webbing above will be obvious, and often the webbing has already parted and is visible through a hole.
- One area sinks and the rest does not — A single broken web, or a spring that has come untied at one end. Very common at the front edge of an armchair, which takes the most load from people perching.
- You can feel individual springs through the seat — The stuffing above the springs has broken down or migrated, and the spring tops are no longer covered. On a traditional seat the layer that does this job is a hessian over the springs plus a layer of fibre or hair; both are replaceable and this is ordinary wear rather than damage.
- A metallic twang or scrape when you sit — Springs touching each other or touching the frame, because the lashing twine that held them apart has perished. Distinct from a creak, which is timber.
- A dry creak, especially when you lean or twist — A frame joint. Grip the arms and rack the chair gently side to side — real movement at a joint means the frame needs regluing, and that means the chair must be stripped and taken apart regardless of what the upholstery needs.
- The seat is hard and unyielding rather than soft — Often a previous repair: springs overtied, a board fitted across the frame, or foam packed in over a collapsed traditional seat. Extremely common on inherited furniture and usually the reason it is uncomfortable.
- Fine dust, small holes, or a musty smell — Insect activity or damp in the stuffing, particularly in older pieces with hair or fibre filling. This changes the job substantially and it changes how the strip should be handled.
- Rewebbing only — The best outcome. Strip the dust cover, replace the webbing, retie or re-secure the springs, and reinstate. A weekend for a dining chair, longer for an armchair, and the top cover may survive untouched.
- Rewebbing and re-lashing springs — The common case on anything Victorian. Add the skill of tying springs, which is the traditional craft’s central technique and is best learned on a dining chair rather than on the armchair you love.
- Full strip and rebuild — Everything off, back to frame. This is the real project and it is where the craft actually lives — but it is also where cost appears, because a full set of materials and a good cover fabric for an armchair is a serious sum before any labour.
- Frame repair first — A loose frame must be dismantled, cleaned of old glue and reglued. This is a woodwork job inside an upholstery project, and skipping it guarantees that the finished chair fails.
- Not worth it — A frame made of stapled softwood and particle board, a piece with active insect damage in structural members, or a modern flat-pack sofa. These exist and recognising them early is a skill rather than a defeat.
Questions this guide answers
Listed so you can tell at a glance whether this is the page you wanted. HobbyHQ keeps one guide per question family rather than a page per phrasing.
- why does my armchair seat sag
- what does a lumpy chair seat mean
- why does my chair creak when I sit down
- how do I know if a chair is worth reupholstering
- what is wrong with the springs in my sofa
- do I need to replace the webbing on a chair
Part of Upholstery. Last reviewed 2026-08-20.