The replacement units are made to measure in the Andersen factory. The survey form is very thorough and makes the job of measuring up very easy. As well as the height and width you also need to measure the sill angle and check the window is square. Andersen can supply you with a very handy pendulum angle finder to do this. You can chose from a variety of exterior colours including white and three natural wood interiors or a white finish. The exterior finish in our job is Sandtone which matches the exterior stonework. The exterior surface is made from a reconstituted wood/resin product called Fibrex® which is perfectly stable and resistant to decay. It never needs painting but if you ever want to paint it you can. The Fibrex® trims cover the old frame completely and are easily ripped down to suit the dimensions of the margin. They are then stuck in place with mastic such as Ceresit FT 101 or Evode Sticks Like.

The most obvious difference between these tilt and slide units and traditional cord hung sashes is the lack of staff bead over the gap between the sash and frame. If you prefer the traditional look and are willing to forgo the tilt facility (which allows you to clean the windows from inside) then you can chamfer covers to resemble staff beads. The only remaining giveaway is the lack of sash cords. You would expect to see spiral balances (which I hate) in place of the cords but Andersen uses a far superior system of blocks and tackles housed in the sashes. The glazing bar options are basically whatever you want them to be. The sealed units are single pieces of glass with external and internal bars stuck on and internal spacers set between the panes to coincide with the glazing bars which adds authenticity.