We get this question a lot relative to spindle and bow back chairs. Some of our seating options do not include an upholstery option because of the seat design. In most cases, we can add upholstery, but not in a traditional way.
When a chair's spindles attach directly through the seat, upholstery cannot be added on the rear edge. Doing so would damage the upholstery and interfere with the the design of the chair. To combat this difficulty, Early American furniture builders used a technique called "tack on" which means that roughly 85% of the seat surface would be padded and the upholstery then, literally, tacked to the seat. This is period correct and Countryside offers this on virtually all of our bow back or spindle chairs.
Most chair designs after the mid 20th century utilize an upholstery method in which the actual seat of the chair can be separated from the frame. Removing the wood seat allows for a higher quality foam or padding to be attached to the seat and a better "fit" of the fabric or leather to the seat is possible since the chair is not fully assembled when the upholstery is applied. The majority of Countryside's chairs are upholstered in this way. The upholstered seat, then, is later attached with corner bracing and screws.
A third upholstery process is "full" upholstery where even most of the frame is covered by fabric or leather. Only the legs are exposed and this method often produces an extremely comfortable chair. More foam can be applied to both the seat and back of the chair and fabric is stretched and seamed before final assembly. Though nail head trim is sometimes applied in this upholstery method, it is typically for aesthetics and not for attachment purposes as in "tack on" upholstery.
We hope this answers the question! See our entire colleciton of upholstered dining chairs here.