Common mistakes made when ordering windows and doors

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Common mistakes made when ordering windows and doors (this list is not exhaustive, we’ve just provided some examples of mistakes we’re aware of)

  1. If large bi-fold doors are used, the hinge jamb (the side the panels stack when open) will be subject to a heavy load when the doors are open (especially doors with 5 or more panels) and so we recommend using concrete blocks or bricks, not lightweight blocks.
  2. Are lead flashings or lead trays being used. A common oversight is that the build-up of lead in the corners can cause a pinch point or snag the frames.
  3. If elevations are clad differently, different cill extension might be required (e.g. timber weatherboarding might be at first floor level only, so first floor windows will need deeper cills)
  4. Leave enough floor clearance for inward opening doors, this problem often occurs when mobility thresholds are specified and the floor heights are not adjusted to allow clearance of the door, resulting in the need to trim the door/s which is not always possible.
  5. Check for clearance of trickle vents if fitted to window heads. It might be necessary to add an extension fillet to the head of the frame to allow the trickle vent to sit clear of the internal plasterboard and plaster finish. Alternatively specify vents fitted to opening sashes, or avoid vents altogether by installing a heat recovery system.
  6. Take care (when replacing wider profile frames with slimmer profile frames) that the new frames do not become hidden internally, especially by the internal window board or tiling.
  7. Check that the depths of new frames are not too wide for replacement projects (some triple glazed systems can be 100mm or more deep and cause problems if the old frames are considerably smaller).
  8. It can be prudent on large replacement projects to change 1 or 2 frames as a test bed. It can help by removing any guesswork concerning how the frames to be removed were initially installed. Particularly relevant for sliding sash windows.
  9. Access. Can the delivery vehicle get onto the site, can larger frames be transported into position, is a telehandler or crane required? As patio door frames become large and heavier these questions should be considered at the outset.
  10. Are towers or scaffold required for access?
  11. Does the frame fit the aperture? It should be simple enough but so often frames arrive on site and it transpires only 1 measurement has been supplied to both the builder and the frame fabricator, so the frames won’t fit in the holes. Make sure the builder knows to make his openings larger than the frame by correctly labelling the frame dimensions as “final manufactured frame sizes”. Also see measuring guide below.
  12. Don’t forget that each bedroom will require one sash to provide an escape option in the event of a fire (an egress window). If friction/scissor hinges are used, escape egress hinges will probably be required for these openers.


Measuring guide

Please provide the shortest of 3 measurements for both width & height, look for irregular bricks and use a spirit level to make sure the openings are built square (if they are not either the opening or frame might need to be re-sized).

The new window will be manufactured to fit  the opening with a tolerance of  5-10mm i.e. a window measuring 915mm wide x 900mm high will require a structural opening/aperture of 920-925mm x 905-910mm.

Please take into account particularly wide openings (bifold/sliding doors) need to have a level base, especially when a flush floor finish is required. We have often seen sloping floors, even in new builds, which make it impossible to install a 3000mm+ wide door with a threshold which is flush.]



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