This 1931 weatherboard house still with its garden "sleepout" has high local significance as a typical and intact example of the houses built throughout the Dandenongs during the inter-war years. It is notable for its garden designed by a botanist and her husband, which retains many original features including a glasshouse with the remains of a coke-fired iron boiler used for processing water for plant propagation, and a considerable part of the original garden plantings.

Hillside is a modest timber dwelling located south of Monbulk Road and south-east of the small Upwey commercial centre. It is set well back from Hillside Grove within a densely planted garden. The garden contains many large, mature indigenous and imported trees and shrubs, including rhododendrons, azaleas, camellias as well as beeches, elms, liquidambars, blackwoods and tree ferns. Several lawn areas remain to the north of the house. The garden contains a delightful collection of trees and shrubs, most dating from the Bonnell's period of ownership. The overall design is informal, with gently curving paths, some edged with stonework. A series of stone ponds catch the heavier rainfalls. The garden extends across the present property boundary into the adjoining property at 7 Hillside Grove. The garden extends to the west to Ferny Creek and a vegetable garden now occupies the area where the Bonnell's kept chickens and turkeys.

The glasshouse, built in 1950, is a testiment to the dedication of Madge Bonnell in creating this garden. The base of the propagating stand and the boiler survive, along with the brick base walls. The upper walls and roof structure were recently rebuilt. There are also two outbuildings, one being a bungalow from the Bonnell's period of ownership.

Hillside is a L-shaped, single storey timber house which has undergone a number of alterations and additions since its construction in the 1930s. It is a typical example of timber houses from this period and includes a gabled roof and horizontal weatherboard lining. The small roof overhang is edged with simple timber bargeboards and the gable end includes dark stained timber shingles which sit proud of the exterior of the timber wall. Windows are rectangular and timber framed with multi-paned casements either side of a larger, fixed panes. The moulded timber surrounds are fixed to the outside of the wall and have simple timber brackets to the underside. A small verandah which links the main transverse gable to the projecting wing is elevated and timber lined and marks the original front entrance. A skillion roofed addition to the north of the house extends beyond the original building line and now incorporates the main entrance.

The interior of the house includes a number of original features. The main living room retains a tapestry brick fireplace, elaborately moulded plaster ceiling, plate rails and original doors and windows. Original features are also found throughout the house.

A glasshouse is located adjacent to the house which has been reconstructed in recent years. It includes the remains of a coke boiler to the rear of the building.

Physical Conditions: Good

Integrity: Evidence of stages