A cavity wall has two layers of brick, with a gap in between. The gap can be anything from 20mm to 100mm wide. Homes built form the 1950’s onwards are usually of Cavity Wall construction.
Other wall types
If your home is made of stone (ie granite, slate & sandstone etc), system built, concrete slab, timber, steel or any other material, please select solid walls. If you have cob walls they do not need insulating.