Because the width of each step and platt stone is often as much as eight feet (2.5 metres), renewal can be expensive; minor damage is best left undisturbed, unless it affects the stability of railings or masonry.
Worn treads and damaged nosings can be ignored unless they constitute a hazard.
Many steps and platts are badly worn and the soffit may have been softened and laminated due to water seeping through the joints; rooms added under the steps may suffer from chronic and incurable dampness.
The arches and platts may have been weakened by settlement of the area retaining wall or, less commonly, by movement in the front wall of the building.
The ends of stone steps often laminate and they may be split by rusting iron balusters.
Damaged steps down to basement areas should be renewed in stone; however, if only the tread is badly worn and the stone is otherwise sound, the surface may be levelled with an epoxy screed.
Localised areas of wear or damage can be repaired by cutting back to a sound base and inserting a new stone indent bedded in epoxy resin.
All paving stones become worn and it may be necessary to dress and buff an indented stone to match the worn profile. More extensive damage should be remedied by renewing whole stones, although only a few quarries can supply stone in such long lengths.
If the stone around the base of cast-iron balusters has spalled off, it can be built up with a suitable mortar repair mix around an armature of copper wire, but it is better if the stone can be cut back to receive a new indent fixed with stainless-steel dowels and epoxy resin.
With either method, the baluster should be removed, rust-proofed and reset in a new hole. If there is extensive damage to the edges of exceptionally long steps and platts, it may be necessary to cut back the ends by some 150 mm and refix the railings 100 mm from the newly formed edge.
This repair requires an extra length of railing to be inserted on each side of the steps at the pavement; where the railings are complex, this may be difficult and expensive.
If leaks are damaging a room in the basement below the platt, it may be worth repointing the joints, although this will not be a permanent cure because, when new, the stones were butted without any form of waterproofing.
The existing mortar should be raked out to a depth of at least 50 mm, all loose mortar removed and the joints washed out, repointed with lime mortar and finished with silicone or polysulphide mastic applied by a gun to a depth of about 20 mm.
The conspicuous position and frequent use of the steps and platts means that cheaper substitute materials are unsatisfactory; cement screeds, reinforced concrete, thin applied flagstones, etc., are all unacceptable and unlikely to obtain Listed Building Consent.
On no account should the bases of the balusters be secured by a concrete haunching built up along the sides of the steps and platt.
Most ground floors in the Birkenhead are above pavement level; the ‘common stair’ or ‘main door’ is entered across a stone arched bridge carrying a stone platt (paving) and steps, and there are stone steps down from street level to the basement areas.