When building a home extension, one of the structural decisions that will be made is whether to construct the external walls in timber frame or traditional masonry. While this decision is sometimes made by the contractor based on their preferred method of working, it is worth understanding the differences so you can have an informed conversation with your builder.
Traditional masonry construction uses brick and blockwork to build the external walls. The external leaf is typically facing brick, chosen to match or complement the existing house, and the internal leaf is typically insulated blockwork with a cavity between them. Masonry is well understood by most builders, the materials are readily available, and the construction is robust and long-lasting. Masonry walls also provide excellent thermal mass, which can help moderate temperature swings inside the building.
Timber frame construction uses a structural timber panel or frame to form the wall structure, with insulation between and around the timber members, a vapour control layer, and external cladding. The cladding can be brick slips, render, weatherboard, or other materials to match the character of the house. Timber frame extensions can be built faster than masonry because the panels can be prefabricated off site and erected quickly on the plot.
For residential extensions in London, masonry is the more common choice, partly because most existing houses are masonry and clients want the extension to match in appearance and construction type, and partly because brick matching is easier when the external leaf is genuine brickwork. Timber frame is more commonly used for larger new build projects where speed of construction is a significant benefit.
From a thermal performance perspective, both systems can achieve the same insulation levels required by building regulations, though timber frame can achieve higher levels of insulation more easily because the frame itself can accommodate thicker insulation. Masonry walls are limited in how much cavity insulation can be used without risks of moisture bridging.
For retrofit and extension purposes, both systems are suitable and the choice often comes down to the specific project requirements, the contractor preference, material availability, and whether matching the appearance of the existing house is a priority.
RCB Design and Build uses both masonry and timber frame construction depending on the requirements of each project. We advise clients on the most appropriate construction method at the pre-construction stage and ensure the chosen system meets all relevant building regulation requirements.