How Do I Know If I Have Cavity Walls, Or If They Have Been Filled?
Assuming you’re in a house with brick external walls: If the bricks are all lying length wise (so no short sides showing) this is a clear sign of cavity walls. Houses that are built from solid brick (double layers of brick) will have walls showing a few long sides of the bricks, then a short side, then a few long sides, etc. See this page for examples: www.thinksulation.co.uk Checking whether the cavities have been filled is harder. If you have windows replaced you will be able to view into the cavity to see for yourself. The filling is usually a yellowy material that will be noticeably different from the solid brick or concrete either side. You can also try to peer down the cavity from your loft, this may involve crawling out over ceiling joists and trying to angle a mirror and torch so that you can see under the eaves and down the cavity. If you ever need to drill through the walls, a small am
