Why is roller blind fabric narrower than the overall blind width?
Updated
A roller blind's fabric is narrower than the blind overall because the tube ends, the brackets and the control mechanism need room at each end. The fabric sits between them. That leaves a narrow strip down each side of the blind where light can show.
A roller blind is more than its fabric. Along the top is a tube that the fabric rolls onto. At each end of the tube there is a fitting that carries it, and one end holds the control, such as a chain mechanism or a motor. The brackets hold those ends to the wall, the ceiling or the window frame.
Where the width goes
The overall width of a blind is measured across the whole tube and its end fittings, from bracket to bracket. The fabric is only the part between the fittings, so it is narrower than the overall width. That is how every roller blind is made. It is why the size of a blind is described in two ways: the overall width and the fabric width.
What it means for light
Because the fabric stops short of the ends, a small strip at each side is not covered by fabric. In a recess, the blind sits inside the reveal with a gap down each side, and light shows through. On a blockout blind that strip is easy to see in a dark room. It is not a fault in the fabric. It comes from how any roller blind is built and fitted.
Ways to reduce the side gaps
- Fit the blind outside the frame, with an overlap past the opening on every side.
- Fit the blind close to the glass with the fabric rolling off the back of the tube, called back roll.
- Add a curtain in front of the blind, which covers the side gaps.
Makers and retailers differ on which width they ask for when a blind is ordered, so the order has to say which one it is. Mixing them up gives a blind that does not fit. Your retailer takes the measure and writes the size on the order.
Speedy Blinds makes roller blinds for retailers. Ask your retailer how wide the strip of side light will be on your window and what they recommend.
Other ways people ask this
Is the fabric width the same as the blind width?
No. The fabric width is the part between the end fittings. The overall width includes them.
How do I stop light at the sides of a roller blind?
Fit it outside the frame with an overlap, or put a curtain in front.
Do blockout roller blinds block all light?
The fabric can. The blind as fitted does not, because of the side gaps.
This answer is general information. For your own windows, your retailer's advice and your order with them come first.