Building 13 (North Barrack Block), South Barracks

Building 13, also known as the North Barrack Block, is an infantry barracks that now serves as Royal Marines barracks. It was constructed in 1795 by architects J Johnson and J Sanders for the Barrack Department and has been used as Royal Marines barracks since 1869. The building underwent alterations in the mid-20th century. It is made of brick and features brick lateral stacks at both ends, two at the front, and a central ridge stack, all topped with a slate hipped roof. The structure has a double-depth plan and is designed in a mid-Georgian style, standing three storeys tall with a ten-window range.

The exterior is symmetrical, showcasing segmental brick arches over doorways located three bays from the ends, which have mid-20th century doors. The windows include 6/6-pane sashes and 3/3-pane sashes on the second floor, some of which are horned. There are also two lead-clad dormers with casements. The returns of the building have two blind windows, while the rear has been extensively rebuilt but retains similar window features and six dormers like those at the front.

The interior has been significantly altered from its original state, which included stairs leading from the entrances. Historically, this barracks was part of a large complex built to accommodate over 2,000 men during the country's first barrack-building campaign. Along with slightly earlier blocks at Hounslow, this is the only surviving example from that period for infantry barracks, and it is listed for its historical significance alongside the Officers' Mess and Cavalry Barracks.