Proportions and planning
 The Encyclopaedia of Curtains, page 114
© Copyright Merrick & Day

Design decisions include how far on either side of the window to extend the pelmet board or pole, how long to make the valance, and so on. All play an important part in the success of any window treatment.

Once you understand how the curtain proportions can be altered to suit the window, where to position the brackets or poles, then the finished curtains will make a beautifully balanced statement. Here are some questions for you to consider while still at the measuring stage and before you make up your mind about fabric, hardware, style, and design. Make a note on the Measuring Chart of any appropriate suggestions. Before purchasing your tracks, boards or poles, see Fitting, pp225-227.

What height above window?

Any dead wall space above the window can be fully utilised and covered with a valance or pelmet to achieve a more elegant effect. In standard situations, the pelmet board should be positioned directly underneath the coving or cornice; the pelmet itself or the valance or swag should be between 1/6 to 1/5 of the finished curtain length - it should just cover the frame to lose as little light as possible during the day.

If the valance you have planned doesn't quite cover the top of the window, lower the position of the pelmet board until it does. You can use a piece of lining fabric tacked in the right position to see how it looks.

How long, including stack back, should they be?

STACK BACK is the area where the curtains hang against the wall when they are pulled open. By covering the wall and not the glass, during the day, it allows the most light into the room.

Corded tracks and poles require more wall allowance than un-corded. The curtains can only stack back on the track or pole between the cord housing and the overlap arms.

EASY FORMULA To determine the length of the track or pole, increase the width of the window glass area by 30%. Very full curtains need more stack back space than flatter ones, and heavier fabrics will also take up more stack back area. You can adjust the 30% to take this into account.

What height above window?

Laths and poles have the advantage that they can be fixed at window level if there is no available space above. They can even be ceiling fixed if necessary. Ideally, the top of the lath or pole should be fitted 10-20cm (4-8in) above the window.

Poles can be fitted into the ceiling joists, with brackets that have a top fitting. The pole is slotted through the brackets. Make sure the fitting is secure, because a set of lined and interlined curtains can be a considerable weight, and simple plasterboard or unsupported boards will not hold them. Poles can also be fitted up to the ceiling with overclip brackets. They are held by the clips, rather than resting on brackets.

How long should they be?

Curtains look their most imposing when they are full length, either touching the floor or falling generously onto it. If they are going to be held in tie-backs, ombras or curtain bands, make them 2.5-5cm (l-2in) longer, so they can be bloused above the holder.

Curtains that puddle onto the floor will need arranging each time they are opened and closed, or they can look messy. Corded tracks should not be weighed down with too much extra length as it may strain the fixing. Covered laths look tailored and smart when the curtains just touch the floor.

Sill length curtains can be recessed into the frame and touch the sill, or fixed outside the frame, and hang I0-I5cm (4-6in) below the sill. This is sometimes called 'apron length' and ensures light and draught exclusion.