Depending on which underfloor heating system you choose will depend on how much your floor is raised. Electric underfloor heating mats are only a few millimetres thick and can be installed within a layer of screed, adhesive or levelling compound used to fit your floor covering, which means your floors will not be raised. However if you are installing this onto an existing floor, then you need to be prepared that your floor may raise more than just a few millimetres, taking into consideration any materials used to cover the heating mats. Wet underfloor systems are typically installed in the subfloor, and will utilise heating pipes which are thicker than electric heating mats, meaning your floor will be raised a lot higher. You will also need to take into consideration any additional insulation which can also have an impact on your floor level.