Sandown Fort was also called the Granite Fort was located in the centre of the beach at Sandown Bay. Sandown Granite Fort was recommended by the Royal Commission of 1859 and was built between April 1961 and September 1864 at a cost of £73,876. The Fort was built to mount eighteen 9-inch RML guns in casemates with armoured shields facing towards the beach. This was similar in design to Hurst Castle in respect of these casemates. It was proposed that there would be additional guns on the roof above these casemates. The whole works was protected by a a dry ditch and enceinte wall. Four caponiers covered this dry ditch.
In 1881 it was proposed to replace the 9-inch RML guns with 10-inch guns and increase the shield armour by 5-inches. By 1886 the Fort was armed with eight 10-inch RML and four 9-inch RML guns. Two 10-inch guns were moved to Sandown Barrack Battery and mounted on hight angel mounts. The two vacant positions were filled with concrete to act as traverses to protect the remaining casemates from incoming fire.
Returns from 1891 show the armament of Sandown Fort to be six 10-inch and two 9-inch RML guns. In 1897 there were proposals to mount three 3-pdr Q.F. guns on the roof of the armoured casemates. These guns were to be moved from Hurst Castle but it is not known if this moved was ever completed.
By 1895 armament was increased by two 64-pdr RML guns, a 32-pdr SB and a 8-inch SB gun, but these additions are thought to have been for training purposes. By 1895 the two SB guns had been removed to be replaced by a single 9-pdr RML gun.
By 1904 the RML had all been removed and the casemates used for six 5-inch BL guns for training purposes. At this time three 3-pdr Q.F. guns were on the roof of the casemates, again for practice purposes. The remainder of the fort was used for accommodation and storage.
The whole Fort was sold off in 1930 and most of the rear areas of the enceinte were destroyed. However, some of the casemates survives and the roof of one of the casemates can be seen.