Woven rush is one of the sturdiest traditional methods for making a chair seat with a little give to it for comfort. When a rush seat does begin to come apart, however, it quickly becomes unusable and must be completely replaced. Fortunately, weaving a new rush seat is easier than it may look, and newer materials function well at lower prices than the natural rush made from cattails.
Cut whatever remains of the old seat off the chair frame. Check for tacks holding it on underneath, but don't be concerned about smoothness of the rails.
Lay the end of the rush across one of the rails, snug against the corner and with about 4 inches extending into the space the seat will cover. Wrap the longer end around that rail, bring it up into the centre, and draw it across the top of the tail and the other rail that makes that corner. Go around the second rail, close to the corner post of the chair, and under again into the centre.
Draw the rush across parallel to the first rail and lift it over the rail at the next corner. Holding the rush close to that corner post, wrap it around the third rail back into the centre and then back over the top of the first run and the first rail to come up again in the centre from underneath.
Wrap the rush the same way around each of the other corners, running parallel to the last rail, over the top of the next, over the rush and the last rail, and up in the centre again after turning the corner.
Continue in this manner around the seat, working inward from the four corners and keeping each round closely parallel to the last. Come up each time in the shrinking centre square. Attach new strands, as needed, on the underside and fasten the end there securely.
Drive a tack through the rush into the bottom of the chair rail at any point for more security, or to hold the rush while you take a break. The weave actually forms two layers, above and below the rails. You can fill this for extra padding, with shredded rush or crumpled paper. Finer old chairs with rush seats may have split rails that require you to thread the rush through instead of wrapping al the way around. Rush seats can also be replaced with wider ash or paper splints or Shaker tape, which have their own traditional weaving patterns.
Natural rush must be soaked in water before weaving; fibre rush, being paper, must not be and will not hold up if the chair is left outside.