Zig Zag Springs (also known as No-sag or Serpentine springs are used a lot in modern furniture .
A minimum of 5 springs should be used under each seating area i.e. chair = 5 springs, 2 seater sofa =10 springs. However the more zig zag springs used the firmer the seat.
When the zig zag springs are fitted across the seat they should be almost flat with just a slight dome upwards and all the zig zag springs should then be tied into place with Laid / Lashing Cord, three rows across a normal size seat. This makes the zig zag springs act as a unit instead of individually, which can cause them to break easier.
The zig zag springs are then covered with hessian and a padding, we recommend Typar Backed Felt as it is very strong and easy to use. The seat can then be covered with calico and/ or your top cover. The zig zag springs are stocked in standard sizes but can be easily cut with a hacksaw if you need to adjust the size.