Standard Construction Drawings

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What are the issues?

A typical dwelling built to 2006 standards loses more than 30% of its heat through junctions and around window openings by a process called ‘thermal bridging’.

For the first time in 2013, Building Regulations began to measure heat loss through junctions, this is measured by Y-values (also known as ‘psi’ values). The Y-value in each SAP assessment has a big effect on build materials and cost. If you don’t understand Y-values in your build, you may be paying unnecessary costs.

What is our solution?

We have created 80 new build Standard Construction Drawings with the lowest Y-values for SAP. They can save you time and money and use traditional building techniques. Architects can easily use them in their CAD drawings.

Are they useful for me?

  • The drawings are relevant for anyone involved in new build design
  • Helps reduce the cost of building materials
  • Helps reduce energy bills for the owner
  • Use traditional masonry building techniques
  • Are free to download

  • Are available on CAD for architects
  • Have low Y-values for SAP Assessment
  • Have a clear checklist for builders
  • Are registered with, and supported by, LABC
  • A menu of options are available

Why are the Y-values important?

Heat loss in Buildings

Within buildings the heat loss through junctions is known as ‘thermal bridging’. In a poorly insulated property heat loss through thermal bridging is not significant. In highly insulated walls (with low ‘u-values’), the heat loss through junctions, where several components are assembled together, can be very significant if they are not well designed.

SAP 2012

the right Y-values in the SAP Assessment of your new build should be a key priority. If you don’t make any plans for this, the SAP Assessor will use ‘Default’ Y-values. With ‘Default’ values, the SAP software assumes your junctions will lose as much heat as having a 3m₂ hole in your wall. This means they will need to specify much thicker insulation to compensate. By using the Travis Perkins modelled junctions you can significantly reduce your Y-values and save up to £40 p/m₂ in build costs.


On a cold day, you may be equally as warm in a thick jacket with the zip open as you would be in a thinner jack with the zip closed.

This is because heat escapes via the path of least resistance. Thermal bridging offers this.

Our drawings reduce the need to have thickly insulated walls, as they use a thermally modelled solutions to achieve the same result.

Insterested? Here’s what you need to do...

  • Choose correct construction drawing for you specification
  • Incorporate construction drawings into your design
  • with the SAP assessor, choose a heating source from our menu of options
  • Pass all relevant construction drawings & appendices to SAP assessor
  • Incorporate all relevant information into construction pack
SAP Assessor
  • Use PSI & U-values from specified construction drawings
  • Select the air tightness level and apply to SAP calculation
  • Inform architect of options for the heating source
  • Press all SAP calculations to architect & builder
  • Incorporate all relevant information into construction pack
  • Download the relevant construction drawings as per construction pack
  • Review specified construction drawings and checklist and read instructions
  • Familiarise yourself with animations and information on SBS website
  • Build using specified products which are available from Travis Perkins
  • Return signed checklist to SAP assessor for audit purposes
Self Builder
  • Talk to your architect, SAP assessor and builder about how best to use the construction drawings in your build design

What are the benefits?

Architects/SAP Assessors

  • FREE to use
  • Fits your bespoke plans
  • Available in CAD
  • Very low Y-values
  • Makes passing SAP easier


  • FREE to use
  • Specified product list of traditional building materials
  • Easy to use guides for building
  • 120 designs for all types of masonry construction
  • Available in CAD

Property Owners

  • Fewer draughts
  • Use less energy
  • Lower running costs
  • Create warmer homes
  • FREE to use