Notching and Drilling of Timber Suspended Floors when installing Underfloor Heating

It is important that all aspects of installing underfloor heating are actioned correctly and so, below are some guidelines for notching the joists when fitting water underfloor heating systems with a suspended wood floor. We also recommend that you always check with your builder for the correct procedure.

1. Holes should only be drilled on the centre-line of the joist, as this is where the compressive and tensile load distributions are neutralised.

2. The holes should have a diameter of no greater than 0.25 times the depth of the joist and should be no closer together than 3 times the largest diameter permitted.

3. They should be drilled no closer to the support than 0.25 times the span and no further away than 0.4 times the span.

4. Notches should only be made in the top edge of the joist and should be no deeper than 0.125 times the depth of the joist. Do not drill within 100 mm of the notch.

5. Notches should be no closer to the structure supporting the joist than 0.07 times their own span and no further away than 0.25 times the span. This is to avoid the area of maximum shear force and the area of maximum bending in the joists. On no account should an attic truss joist be notched.

For further assistance on how to action this correctly, feel free to contact a member of our helpful team.