Fit a Pleated Blind With Luxaflex Duette Fabric in 6 Steps for 90% Light Block

The edge gap that decides the blackout result

Fit a Duette panel inside a recess and light will usually escape down both vertical sides. That slim line at the reveal is the difference between a room reading close to 90 percent darker at the pane centre and one that feels nearer 75 percent, even when the fabric is performing as specified.

Luxaflex rates Duette Architella Blackout fabric at near-total opacity through the cell wall. If the blind falls short across the full opening, the reveal line is normally where the loss occurs. A 4mm gap on each side of a 1000mm-wide blind exposes about 8mm of bare glass, and at midday that strip will appear much brighter than the fabric centre on a basic lux meter.

Order the blind 6mm narrower than the tightest recess width and put a cover detail at the edges. That can be a Duette side-channel or a slim aluminium L-profile painted to match the reveal. In a bedroom briefed for true blackout, the channel is often more important than changing to a higher fabric tier.

The honeycomb cells cut light across the flat glass area. The channel deals with the bright reveal edge left outside the fabric’s reach. Without a channel, even the densest Luxaflex fabric can leave a dawn halo around the recess.

Measure the recess before the order is cut

Run a steel tape across the recess width at the top, the middle, and the sill. Write down all three measurements. Plaster reveals are rarely square, and a 1980s UK opening can vary by 5mm to 9mm from top to bottom.

Use the smallest width as the working figure. Deduct 6mm from that number for a recess fit, so the headrail clears the plaster without scraping. Give Luxaflex the net figure as the exact blind width.

Duette is cut to the size stated on the order. There is no extra factory deduction added later, so the number supplied has to include the clearance you want on site.

For the drop, measure from the inside top of the recess to the sill at the left, centre, and right. A TopDown-BottomUp Duette is less forgiving because the bottom rail needs to sit flat on the sill when fully lowered.

A 4mm slope can show as a wedge of light at one corner. Record it before ordering, because the side channels can only mask the vertical gaps; they will not make a sloping sill disappear.

Also note the reveal depth. A 25mm cell stacks to around 60mm at the head when raised, and a reveal under 70mm can push the stack proud of the plaster line.

Set the brackets so the rail cannot twist

Luxaflex supplies the Duette headrail with uClip or standard fixing brackets, depending on the system ordered. Mark bracket centres 70mm to 100mm in from each end of the headrail. Add an intermediate bracket for every 600mm of width beyond a 1200mm span.

A 1600mm blind therefore takes four brackets. If only the end pair is used, the alloy headrail can bow under the cordless retraction spring. The centre cells then lift away from the glass and reopen the light gap already allowed for during measurement.

Choose the recess top face for drilling, rather than the front reveal. Use a 6mm masonry bit for plug-and-screw fixing into brick, or a 2.5mm pilot into timber lintels.

Set all brackets dead level with a 600mm spirit level laid across the full run. Levelling each bracket separately can compound small errors from one end to the other.

The uClip should snap in with a firm click and sit with zero rock. If the headrail pivots after clipping, the bracket lip has not seated. The blind will hang forward by a degree or two, enough to throw the drop out of plumb.

Clip the headrail and sight the cells

Offer the headrail up at roughly 30 degrees, hook the rear lip into the bracket throat, and rotate the front edge until the uClip captures. Sight along the closed honeycomb from one end: the cell line should read as one straight column, with no fan or twist.

That sight line confirms that the brackets share one plane. A twist in the cells usually means the rail is being held forward or back by one bracket.

Fit the channels, then set the two rails

With the headrail seated, position the slim L-profile or Duette channel down each reveal. Its inner lip should overlap the fabric edge by 3mm to 5mm. Mark screw centres at 250mm intervals, drill 6mm holes, and fix the channel with reveal-matched screws.

That small overlap is the working light seal. The fabric edge sits behind the lip, so direct light cannot track straight down the side gap.

Lower the blind fully at a bright midday and walk the room, looking for vertical bright strips. If a channel lip stands proud and creates its own shadow line, ease it 1mm closer to the glass and re-fix.

A blind cut to fill the recess leaves no space for the channel lip. The fabric can bind against the profile or stop short of it. The 6mm deduction from the recess measurement gives the 3mm overlap on each side somewhere to sit. With the arithmetic wrong, the channel becomes a neat trim piece.

A TopDown-BottomUp Duette has two independent rails. It therefore carries two cord locks and, on a standard system, two operating cords or a single cordless handle per rail.

Pull the bottom rail to the sill and confirm that it meets the sill flat across the full width, using the left, centre, and right drop figures taken earlier. A 3mm rise at one corner is the most common leak left after the side channels are installed.

When one corner floats, the cause is almost always the headrail level set during bracket fixing. Recheck the bracket plane before adjusting anything else.

Drop the top rail down from the head and watch the upper cells compress against the headrail seal. On blackout systems, Luxaflex fits a light-seal strip at the head. A bright line across the very top means the headrail is sitting forward of the reveal top and the brackets need reseating.

Cycle both rails through their full travel three or four times. A new honeycomb stack is stiff, and the pleats need working before they settle into an even concertina without gaps between individual cells.

Read the result against a number

Luxaflex markets the Duette blackout range as room-darkening to near-blackout. In a real recess fit with side channels, the practical result is around 90 percent light reduction measured at the pane centre, with weaker readings toward any unsealed corner.

A cheap lux meter or a phone light-sensor app will show the difference plainly. The fabric centre may read in single-digit lux, yet the bare reveal beside it can sit at several hundred.

The honeycomb air pocket also gives a small thermal benefit. Still air trapped inside a 25mm cell resists conductive loss through cold glass much as a Knauf Earthwool roll resists it through a loft floor. The blind value remains a fraction of a properly insulated ceiling, and selling it as a heating fix overstates the effect.

If the reading lands below 90 percent, examine the sill corners, the channel overlap, and the head seal before assuming the fabric tier is to blame. A bright vertical strip points to the side detail; a bright line across the top points to the headrail seat.

What the lux meter rarely supplies is attribution. The meter gives a reading, yet the origin of the strip remains a separate problem.