Gothic style, highly picturesque in conception and detail. Five-stage octagonal tower narrowing at the upper 2 stages, with buttresses and higher W circular stair turret, with S wing of 2 storeys with attic and a gateway at right angles to wing. Of rock-faced Cefn stone with ashlar dressings. The buttresses are stepped and end at the upper stage with crocketed pinnacles set diagonally. The Tower has an embattled parapet, beneath which is a frieze of heads interspersed with shield-bearing angels, and which continues across the stair turret. Above the frieze the turret is hexagonal and has open cusped lancets in each face, with continuous sill band. The parapet is embattled above a string course with grotesques at the angles. In the upper stage of the tower are tall cross-windows. The turret has a balcony at this stage on large brackets with a balustrade consisting of 2 tiers of arcading. Above the balcony is a string course below a small lancet in an ashlar gable the S face. In the stage below, the tower has blind arrow slits alternating with small sash windows with cusped heads, beneath which is a frieze of blind quatrefoils continuing across the stair turret. In the stage below are larger cusped lancets alternating with large blind arrow loops, except for the E side which has a quatrefoil in a square panel with hood mould. In the lower 2 stages the details are confined to the 3 faces on E side, facing the garden. In the upper of the 2 stages is a balcony with arched openings in the buttresses. It has a parapet of pierced quatrefoils, a soffit of foiled panels and is carried by large brackets on head corbels. In the E face is a single-light window with stylised Decorated tracery (consisting of 2 mouchettes). Above it is a blank shield and the Naylor monogram (ICN) in relief beneath a trefoiled gable, and with foliage in relief and a fleur de lys finial. To L and R are blind stylised trefoil windows. In the lower stage is a door with studded ironwork flanked by shallow niches in the buttresses. In the faces to L and R are 2-light mullioned windows with Y-tracery and sill bands. The lower stages of the tower have plainer windows on the W side facing the courtyard, in contrast to the rich treatment of the E side facing the garden. The turret has tall narrow openings in the lower storeys.
The S wing has a garden front to E with an advanced gable to L and 3-window range to R. In the lower storey the bay to L has 2x 4-light mullioned windows with cinquefoil heads, with plainer 2-light mullioned windows in the upper storey under hood moulds and a single 2-light round-headed mullioned window in the attic. To R are 2-light mullioned windows with pointed heads and hood moulds, to L of which is a boarded door beneath a mullioned overlight in a doorway similar to window tracery. In the upper storey are 2-light windows with Y-tracery beneath gablets. Between upper and lower storeys are double continuous string courses. The S or road front consists of a gabled bay advanced from the main axis which has, at upper storey level, a sculpted panel within a 3-bay architrave with hood mould which has diamond stops. It consists of 2 blank shields flanking a large circle with a lozenge in the centre, above which are blind arches with foliage in the spandrels. This is linked with a 3-light mullioned window in an architrave, with a panelled sill incorporating sculpted heads in the attic. The rear entrance front is plainer and consists of ranges either side of a gateway across the service road and at right angles to the axis of the building. To R of the gateway is a 4-window range with 2x2-light windows with Y-tracery in the upper storey beneath gablets while further R are 2x2-light mullioned windows beneath gable, and between which is lozenge with pointed quatrefoil and foliage in relief, and which has a hood mould continuous with the windows. In the attic of the gable is a 2-light round-headed window. The lower storey has 2-light windows. The elevation continues a short distance L of the gateway where it is lower and embattled, and has a doorway to the tower under a segmental pointed head. The S wing has a central stack with 6 tall patterned flues.
The gateway has a 2-centred arch with boarded doors, above which is a coped gable with, on the S face, a sculpture of St George and Dragon. (The gateway is attached to the Library Garden to W. Attached on the N side is the wall of the courtyard to Leighton Hall.)