Suspended Floor

While newbuild homes are built with a concrete base, the majority of homes in the UK have suspended floors, with floorboards laid on wooden joists directly over the ground. These floors allow cold air to rise, creating uneven heat distribution when using radiators. 

Installation of underfloor heating on suspended floors is a straightforward process, but the method used depends largely on the type of joist present in the property. That being said, whether you have standard or engineered joists, there’s a fitting method that can be used to bring warmth into your home. 

Standard Joists

25mm x 25mm battens should be fixed along the length of the joists with 9mm to 18mm plywood laid over the battens so the surface of the plywood is 70mm below the surface of the joists. 40mm insulation is laid over the plywood between joists and pipe is fitted to the insulation. 

Where necessary, the joists are notched to allow the pipe to pass from one bay to another. The pipe is connected to the manifold, relevant tests are carried out to ensure system integrity and the floor covering is laid over the top. The pipes should be encased in an 8:1 blend of sand and cement which should be made level with the tops of the joists.

Engineered Joists

Engineered joists may not be notched to allow the pipe to pass from one bay to another, so a different method must be used. A wooden decking consisting of 18mm plywood or 22mm chipboard must be laid over the joists. Once the decking is in position, the underfloor heating system can be installed using a within-screed, floating floor, or battened floor system.