Category: Design

OIB have designed, made and planted some 12 window boxes in North Parade this year. We are keen to share the design of the box as we think it is a useful tool for the windows of Otley.

The idea was to design a wooden box that fits onto those stone window sills that sit directly on Otley streets but does not require any drilling into the stone structure. We do this by clamping the box against the uprights of the window. This clamp force comes from T nuts and bolts in each end. We consider that this design needs at least 135mm of stone from the window frame to the front edge of the stone window vertical, we call this dimension “D”. Some stone windows are just not suitable as the glass/plastic window frame has been mounted too far forward, or too much damage has occured to the stone.

The first step is to measure “A”, the angle to the vertical, the length of the window box space “L” (minus a couple of mm to allow the box to fit in) and the depth of the stone space “D”. Make a note of any aerial cables, bits of steel in the stone, filler left over from the window installation and other possible problems. Nearly all of these can be overcome by modifying the wooden box.

Measuring Dimension A and D

We base all our designs on treated rough wood 22mm by 150mm. We find 3.6 metres of this is enough for most designs but it is borderline so measure and calculate carefully. If you use too little wood the box ends up too small and dries out during a sunny day.

We then make the end blocks. Each end block consists of a piece to sit inside the box into which most other parts will be screwed and one to sit on the end to support the T nut.

Using our A dimension we can cut these parts of the ends. Then screw one to the other leaving space for the main structure to sit around the interior end.

Using the length L dimension of the window and accounting for the two exterior end pieces we can cut three pieces to make up this structure.

You can now screw the structure together and then drill the ends for the T nuts. They want to be as close to the back surface as possible while still leaving enough space to get access to the bolt head in situ. 35mm seems about right. NB, the nut is hammered in from the outside and the bolt goes through the hole in the end piece to reach the nut. We use M8 zinc electroplated parts and the bolt need sufficient length to get through the end pieces and still have enough clamp distance left on the thread. 65mm seems about right but it depends on quality of stone, tightness of fit etc.

Note the sacrificed hole on the right to fit around an aerial cable.

While you have a large drill with you, please drill a few holes, 2 to 3 large 8 or 9mm diameter, in the base to ensure free draining of the box.

Now find a soft drinks can, any street litter will do, just not damaged. Cut off the ends taking care not to cut yourself. Cut one length and you have a large sheet of aluminium. Cut in half, fold in half and tidy up to remove sharp edges. Bend the top end and voila, a sheet to protect the stone from the bolt ends.

The Blue Peter moment when you get to use a sharp knife..

and now pliers and a hammer.

After the application of a some paint and perhaps an organisation’s logo you can fit it into position. Now all you need is some peat free compost, plants and water.

Note aluminium drops over the box end to sit between the bolt end and the stone.