Invent Design Make

Step 3 – Designing your Doors

You will need to take the measurements of the ‘hole’ that this window or door is going to fill. Take a number of measurements along the height and width. It is likely that they will vary, take the shortest measurements as the ones to work from.

After taking measurements, we can draw up some designs.  I found SketchUp, a free programme, provided by Google, very useful.  If you have the knack of it you could use any other CAD package, or good old fashioned pen, paper and ruler.

This is the stage that you turn your design criteria into an actual design that looks like something.  For example, I wanted my doors to fit in with the rest of the street, so although I might have liked to have some ‘mullions’ (horizontal bracing that runs between the door’s vertical sides)  but this would have looked a bit out of character.

The door must accommodate the large thickness (remember that 52mm?) and weight of a triple glazed sealed unit, so we design that in…

I chose to make the doors in a laminated construction, which, while not to some peoples taste, can offer superior performance in terms of strength and resistance to warping, and is an easy way to make high quality joints that would be difficult without lots of experience and a joinery full of equipment.

I needed to make the two central stiles (the lock stiles) thick enough to easily accommodate the multi-point-locking mechanism (MPL).  Having one is a bonus, because it tightens the door onto the frame’s weatherseal at several points, rather than just in the middles.  This means less draughts, better security, and a door that is less likely to warp because it is held fast all along its central edges.  Below was the original design for the central jamb (where the two doors meet). It just shows the bottom bit – abstractions like this can be useful for working out how bits of wood will fit together.  I realised this was a not deep enough to house the MPL, so it was beefed up a fair bit.

Doing so meant adding a lot of material weight (oak) far away from the hinges = a lot of leverage and force pulling on the top hinges.  To reduce this, and improve thermal performance of the door, I decided that I would come up with some experimental composite design.  Basically this meant working out a way to remove oak, while maintaining strength and adding in a less dense and more insulative material. More on this later…

Below is more or less the final design.  The actual doors ended up slightly different, but If you are interested, you can download my SketchUp design and have a tinker about with it.