The Rectangular Flat Roof with Rooflight Estimating Calculator is used to calculate the Labour, Materials and Plant costs associated with typical Flat Roofs with Rooflights.  

The Rectangular Flat Roof with Rooflight Estimating Calculator calculates the following items:

  • Roof joists and wall plates
  • Fascias and guttering
  • Roof waterproofing and perimeter flashings and drips
  • Guttering and down pipes
  • Plastering and insulation
  • Internal and external decorating
  • Steelwork trimmers and craneage if required to opening
  • Timber trimmers
  • Upstands and flashings around roof light
  • Rooflight
  • Plastering to reveals around the opening
  • Plus all labour associated with the above

This Estimating Calculator is linked to the Specifications.


  • Flat Roofs with Rooflights can be constructed in several different ways with insulation positioned at various levels and utilising a wide variety of insulation and water proofing systems. It is therefore essential that each of these items are carefully examined within the Specification and/or the Calculated Resources tab and adjusted to accommodate the methods you are using.