New carpets require new underlay. Fitting a new carpet to British Standard BS5325 requires the services of a competent carpet fitter. This is extremely important to the life of your carpet.
Woven secondary backed carpets require to be stretched evenly across the room from wall to wall.
For the best results a new and firm underlay should be laid on a clean dry floor, the underlay should be fixed by tacks or tape, with joins butted together. This will stop movement of the underlay when the carpet is laid.
The carpet should be stretched evenly and held on carpet gripper which has been pre-nailed to the perimeter of the room. This will ensure the pile of the carpet will sit upright, giving the best resilience to foot traffic. This also helps to reduce the wear of your carpet.