Sagging seat cushion: check foam, cover and support before replacement

Describe the symptom before ordering foam

A low seat is a symptom, not a foam specification. Start by recording where the depression appears, whether it remains after the seat is unoccupied and whether neighboring units behave differently. Photograph the whole seat and the same area from the side. Include a ruler in a photograph when a dimension is useful, but do not treat perspective as an accurate measurement.

Identify removable and fixed parts before dismantling. Unplug powered furniture and follow its maker’s instructions; leave unfamiliar mechanisms to a qualified repairer. Keep the original position and orientation of a removable cushion so the shop can understand the assembly.

Separate three different questions

First, is the cover loose or distorted? Second, has the core changed shape or feel? Third, does the support below the cushion move or sit unevenly? These questions guide an inspection without diagnosing the problem remotely. A new cover cannot establish that the support is sound, and a new core does not repair a damaged frame.

PFA distinguishes foam density from firmness and describes permanent height loss as compression set. Those terms help you ask for information; they do not identify the cause of a particular sag from a photograph.

Record the core and the cavity

If the manufacturer permits removal, label the cover and core before separating them. Record length, width, depth, corner shape and any wrap or layered construction. Measure a distorted old core in more than one position and mark uncertain measurements instead of presenting them as the original design.

Ask the shop to compare the core with the cover’s seam lines and the seating cavity. Do not automatically order foam to the outer dimensions of a stretched cover. Decide who will establish finished dimensions and what fitting allowance the selected construction needs.

Request a replacement specification

A useful quote identifies product grade, density, firmness test and result, finished dimensions, layers, wrap and intended application. Ask whether the information describes the finished core or a test specimen. Avoid comparing a seller’s word “firm” with another seller’s test value as if they were equivalent.

An illustrative comparison might contain two cores of equal dimensions but different firmness results. Before choosing, request the supplier’s explanation of their use and arrange a trial in the actual cover and support. The example offers a decision method, not a prescribed foam grade or guaranteed lifespan.

Test the assembly before repeating it

For a restaurant with multiple identical-looking seats, approve one numbered unit first. Sit normally, check the front edge and compare seat height with adjacent furniture. Have the shop inspect cover tension and any interference with fixtures. Record observations with the approved construction rather than asking for an undefined “comfortable” result.

If the trial feels wrong, change one agreed factor at a time and retain the previous specification. Changing core, wrap and support simultaneously makes it difficult to understand what altered the feel. Do not cut the remaining units until the revised sample is accepted.

Close the job with a usable record

The final brief should list the numbered pieces, approved core specification, cover work, support repairs, transport and fitting. Include how hidden defects will be authorized and how the shop will handle an unavailable material. Distinguish a repair of the assembly from a foam-only supply order.

At handover, retain before-and-after photos and compare the installed unit with the accepted sample. Ask for care information for the finished piece. Keep a reference offcut or product label when available; future repairs are easier when the actual material can be identified.