Part L 2014 for Wales

Part L 2014 for Wales comes into force on 31 July 2014. The steps outlined in Part L 2014 for Wales in respect of new homes are very similar to those in England but there are some significant differences which will affect those builders who build across both sides of the border.

Part L 2014 for Wales Approved Documents
New Homes

As in England, the new Welsh Part L uses an identical recipe approach for new homes which will benefit those who build both in England and Wales with similar house types.

  Part L 2014 - Wales
Opening area
Same as actual up to 25% of floor area
Ext. Walls (W/m2K)
Party Walls (W/m2k)
Floor (W/m2k)
Roof (W/m2k)
Windows (W/m2k)
1.4 (g=0.63)
Air tightness (m3/hr.m2)
Thermal bridging (W/m2K)
Calculated using the lengths of junctions in the actual dwelling and the psi values provided in Appendix R
Ventilation type
Natural (with extract fans)
Gas Boiler
89.5% (SEDBUK)

The significant difference between the two sets of regulations for new homes is that the Welsh Government are not including a Fabric Energy Efficiency Standard as has been the case in England. To ensure that the fabric of the new home still performs adequately, the elemental backstops have been significantly tightened and are now mandatory so limiting the potential to relax the performance of those elements when altering the 'recipe'. These values are area-weighted averages.

  2010 Value 2014 Mandatory Value
Roof (W/m2.K) 0.20 0.15
Wall (W/m2.K) 0.30 0.21
Floor (W/m2.K) 0.25 0.18
Party Wall (W/m2.K) 0.20 0.2
Windows/Doors (W/m2.K) 2.00 1.6
Air Tightness (m3/hr.m2) 10 10
Existing Homes

Perhaps the most significant changes to Part L 2014 in Wales are the requirements for consequential improvements to existing homes which will affect builders who operate in the domestic home improvement sector.

Alongside strengthening how much existing thermal elements require upgrading when replacing or removing them, there will now be a need to upgrade an existing house if works are carried out to extend the habitable space either by extending, adding a loft conversion or converting the garage. In brief the measures that can be done are:

  • if the dwelling has uninsulated or partially insulated cavity walls, fill with insulation where suitable (may not be suitable for sites exposed to driving rain); and
  • if there is no loft insulation or < 200 mm thick, provide 250 mm insulation or increase it to 250 mm; and
  • upgrade any hot water cylinder insulation as follows:
    • if the hot water cylinder is uninsulated, provide a 160 mm insulated jacket; or
    • if the hot water cylinder has insulated jacket < 100 mm thick, add a further insulated jacket to achieve a total thickness of 160 mm; or
    • if the hot water cylinder has factory-fitted solid foam insulation < 25mm thick, add an 80 mm insulated jacket.

For small extensions less than 10m2 in floor area, the consequential improvement is limited to upgrading the loft insulation only if required.

Transitional Provisions

The new documents will come into effect from 31July 2014 and the transitional provisions for the new documents will be the same as those for the 2010 regulations.

In brief:

  • where building work has commenced on site before 31 July 2014 the provisions of Part L 2014 for Wales will not apply; and
  • where an initial notice, building notice or full plans submission are served before 31 July 2014, the provisions of Part L 2014 will not apply so long as work is commenced on site before 31 July 2015.

Commencement of work

In the Welsh Government's opinion the commencement of work would usually be marked by work such as:

  • excavation for strip or trench foundations or for pad footings
  • digging out and preparation of ground for raft foundations
  • vibro-floatation (stone columns) piling, boring for piles or pile driving
  • drainage work specific to the building(s) concerned.

The Welsh Government considers that the following sorts of work would not be likely to constitute the commencement of work:

  • removal of vegetation, top soil or removal/treatment of contaminated soil
  • demolition of any previous buildings on the site
  • excavation of trial holes
  • dynamic compaction
  • general site servicing works (e.g. roadways).

In some cases applications will be in respect of a number of buildings on a site, for example a number of houses. In such cases it is the commencement of work on the first of the buildings within the application which determines whether all the building work can take advantage of the transitional provisions, not each individual building.

Please talk to your NHBC Surveyor to discuss additional help we can provide and how we can help in registering your sites in time to meet with the transitional provisions.

Where does Part L 2014 for Wales apply?

The Welsh Government has devolved powers to set new building regulations for all of Wales. Subject to the appropriate Transitional Provisions, new building regulations issued by the Welsh Government will be apply in the following Local Authority Areas:

  • Blaenau Gwent
  • Bridgend
  • Caerphilly
  • Cardiff
  • Carmarthenshire
  • Ceredigion
  • Conwy
  • Denbighshire
  • Flintshire
  • Gwynedd
  • Isle of Anglesey
  • Merthyr Tydfil
  • Monmouthshire
  • Neath Port Talbot
  • Newport
  • Pembrokeshire
  • Powys
  • Rhondda Cynon Taf
  • Swansea
  • Torfaen
  • Vale of Glamorgan
  • Wrexham

News Date: 15/07/14