There existed a previous building on the site of what was to become Hammerwood Lodge; foundations and walls in the west of the central block of the current house have been dated to pre-1792, and it would seem likely that this was the principal dwelling of the Bower.

Sperling chose to name the new house Hammerwood Lodge at this point, probably as a romantic reference to the hammer used in the furnace of the iron forge which had existed in the area since the Middle Ages.

"[9] Coadeware plaques of scenes derived from the Borghese Vase adorn both porticos, and the influence of the temples at Paestum, which Latrobe may have witnessed on during prior visit to Naples, and Delos has been noted by scholars.

[8] However, the failure of a large investment in a Dublin distillery led the Sperlings to lose £70,000 (equivalent to approximately £5.9 million in 2021 pounds); the artist and diarist Joseph Farington reported that they and their partners 'overbuilt themselves at a vast expense'.

It would seem likely that extensions to the house, specifically to the north-east service wing, took place under the ownership of the Dorrien Magens family, and census records from the 1840s indicate at least ten indoor staff during the period.

Amongst other more subtle changes to the building, this included raising the attic over the central block to create a low third floor, whilst preserving Latrobe's façade.

Work began on 8 May 1865; scholars Snadon and Fazio comment that "Teulon integrated his additions so carefully with the existing fabric that it is difficult at first glance to discern them".

Whilst maintaining the 2,000-acre estate of parkland, arable farmland and woods, Oswald Augustus also installed a gas system for the lighting of the house, and fully insulated the newly raised roof.

Initially paying for a Chapel of Ease for the three local parishes of East Grinstead, Forest Row and Hartfield, in 1873, he provided for a village school for 100 children; in 1875 for the Vicarage; in 1880 for St Stephen's Church, Hammerwood, to the design of E. P. Loftus Brock, at the cost of £7,431, the first vicar being Rev.

In 1919, the prep school in Tunbridge Wells which the Whidborne children had attended burned down; St Andrew's moved to Hammerwood whilst new premises were found in Forest Row.

[19] In 1921, the remains of the estate – comprising the house and 329 acres of land – were taken up by Lt. Col. Stephen Hungerford Pollen CMG (1868–1935) after a career in the British Army, having been ADC to Lords Lansdowne and Elgin (respective Viceroys of India), winning medals for service in that country and South Africa, and serving in the Tirah Expedition in 1897.

Amid significant vandalism, three tonnes of lead were removed from the roof, compromising it in fourteen locations and allowing thousands of gallons of water to flow into the structure.

The restoration, much of which was undertaken by volunteers,[25] won the Anne de Amodio award from the International Burgen Institute (now part of Europa Nostra) in 1984, and a silver medal from the Société d'Encouragement au Progrès in Paris in 1987.

[30] Guided tours focus upon the historical context of the house, the ancient mythological and religious origins of the Greek Revival, connections with Freemasonry, the Agricultural Revolution, the Picturesque movement, and issues of interpretation of the Borghese Vase, scenes from which are transcribed in Coade stone plaques in the porticos, and the Parthenon Frieze.

An extensive musical instrument collection is used for an annual programme of concerts, and the keyboards are tuned to an unequal temperament, upon which composers of the Classical and Romantic eras relied.

Hammerwood has also been used for fashion shoots and photography for Prada, John Lewis catalogues, Tim Walker for Vogue and editorials for other magazines (including, amongst others, Country Life).

Hammerwood is sited on a south-facing hill, commanding extensive views from the south-west to the south-east; its own southern façade looking across the valley to a stream where the iron forge which gave the estate its name once sat.

A serpentine lake, artificially dammed from this steam apparently as part of the Sperlings' landscaping (not shown on a Gardner and Gream map of 1795 but visible on the OS drawing of 1808)[36] sits at the bottom of the valley with open parkland on either side; views of distant hills continue for two or three miles beyond.

[8] The influence of Capability Brown has also been noted, and ring counts of oaks felled by the Great Storm of 1987 dated them to 1793 and 1796, suggesting that landscaping and replanting did indeed take place.

[5] Additional formal terraces and informal ornamental gardens were made up in the 19th and 20th centuries, initially replacing the former sweep of parkland up to the frontage of the house shown on maps up to 1841.

As the cousin of Augustus Smith (the founder of Tresco Abbey Gardens in the Isles of Scilly, where rhododendrons feature in the planting) he introduced them to Hammerwood and they remain today.

He describes the joint endeavours of Sperling and Latrobe as "a collective ego trip on a small budget ... the house, although of modest size for the time, is designed to look huge.