Level a 2.4-Metre Pelmet Board with a Leica Lino L2 on a Bookend Alcove

Why the alcove defeats a short spirit level

Place a 600mm spirit level against the back wall of a bookend alcove and it can read level. Move it 900mm along the same wall and it can read level again while sitting two millimetres lower, simply because the plaster dips between the two positions. A pelmet board spanning 2.4 metres collects those local dips into one long visible slope once fabric hangs from it. Across that width, the eye catches a 3mm fall quickly, especially where the top of a blind sits close to the pelmet edge.

The Leica Lino L2 avoids using the wall as the reference. Its self-levelling horizontal line comes from a pendulum compensator that swings free within roughly plus or minus four degrees of tilt, then locks. The line takes its reference from gravity and stays independent of the room surfaces.

Clamp the unit to a tripod or wall bracket at a convenient height, allow the pendulum to settle, and mark the projected line at both alcove returns plus three or four points between them. Those marks share one true horizontal, so the pelmet board fixings follow the marks regardless of what the plaster is doing behind.

Bookend alcoves have two short return walls facing each other. If the board is fixed hard against a leaning return, the assembly cants forward. The L2 vertical beam lets you check each return for plumb before the first screw goes in.

Setting the laser and transferring the marks

Mount the Lino L2 at around 1.5 metres, roughly where a pelmet usually sits. At that height, the horizontal beam falls close to the working line and remains bright against the wall. In a naturally lit room the red beam washes out past about eight metres, although a 2.4-metre alcove sits well inside that range and needs no detector card. In a bright south-facing room at midday, closing the blinds on adjacent windows lifts the contrast.

With the horizontal line live, mark the left return, the right return, and 600mm intervals across the span. Measure down from each mark to the intended top of the pelmet board with the same steel rule. The resulting points describe a genuinely level line that is unaffected by the wall face behind them.

Snap a pencil line through the points, or run low-tack tape just below the beam on a painted wall you want to keep clean. The tape gives a temporary edge for bracket layout and can come away once the board is fixed.

Use the vertical beam on each return. Hold a short rule against the return face and read the gap between the rule and the beam from top to bottom. A 4mm lean over 300mm of return height means the board needs packing at the front edge on that side, and finding that before bracket fixing saves rework.

Hardwood shims belong behind the bracket because they hold their size under screw torque. Compressible packers can allow the fixing pressure to pull the board back out of true over the following weeks.

Choosing what hangs beneath it

The pelmet hides a heading or a track, and the track choice inside a bay changes the geometry of the whole installation. A curved bay curtain track, bent to the alcove plan on a proper bending jig, keeps the fabric running parallel to the reveal and prevents the fabric from cutting the corner. Silent Gliss and Integra both supply track that can take a bend down to fairly tight radii. The pelmet board depth has to clear the track plus the stackback of the fabric when drawn open, usually 90 to 120mm of clearance for a lined pair.

Blind fabric behaves differently. A roller or Roman blind sits close to the glass, so the pelmet board depth can drop to 70mm. At that point the fabric openness factor drives the specification. A 5 percent openness screen on a roller blind cuts glare while keeping the outside view legible, which suits a bay used as a reading corner. A 3 percent screen closes the view down noticeably; a 10 percent screen weakens afternoon sun control. The pelmet hides the roller tube and brackets either way, while the tube diameter, typically 32mm to 45mm depending on drop, sets the minimum internal depth of the box.

A worked clearance calculation

Take a 2.4-metre pair of lined curtains on a bent bay track. The fabric is a medium-weight woven at 140 grams per square metre, gathered to a fullness of 2.2 times the track length. Stackback for that fabric runs to roughly 18 percent of the track length when fully drawn, so 2.4 metres of track needs about 430mm of stack, split across the two leading edges of the bay.

The track itself sits 40mm off the wall on its brackets. Add the depth of the pleated fabric bunched at the stackback, around 80mm front to back for this weight and fullness, and the pelmet board must project at least 120mm from the wall to clear it without fabric brushing the inner face. Round up to 130mm for the return runs, because the fabric bunches tighter into the alcove corners and needs the extra room.

A shallow board causes the leading edge of the curtain to rub the pelmet return each time it draws. Within a season, that repeated contact can wear a shine into the fabric.

Heading tape and hooks sit about 15mm below the track gliders. The pelmet face needs to drop at least 40mm below the top of the fabric to hide the hardware from a seated eye line. Check the view from chair height, since a sofa-level sightline can reveal a track that looks hidden to someone standing.

Motorising the run

A Somfy Glydea motor turns a bent bay track into a quiet powered run, and its length capacity comfortably covers 2.4 metres of curtain on one motor. The Glydea drives the master carrier along the track at a set speed. Its soft-start and soft-stop keep the fabric from jerking at the ends of travel, protecting the heading and the stitching over thousands of cycles.

Inside a pelmet, cable routing becomes the constraint. The Glydea motor housing adds around 240mm to one end of the track, so the pelmet board on that side needs either a longer overhang or a small removable end cap for access to the limit-setting button and the power feed.

The motor sits inside the box, out of sight, while the mains cable still has to leave the pelmet somewhere. The usual route is through a 10mm hole drilled in the board top into a ceiling void, or down the return into a spur below. Set the travel limits only once the track has been bent and mounted. A limit taken from a straight test track can overshoot the corner after bending, because the bend shortens the effective straight-line travel.

The trickle vent that keeps the reveal dry

A pelmet traps a pocket of still air against the head of the window, and in a room prone to condensation that pocket collects moisture on the cold glass behind the blind. A trickle vent in the window frame moves a small continuous flow of air across that zone, which is trickle vent condensation control working exactly where the pelmet would otherwise create a dead spot.

Where the reveal meets the glazing

If the alcove windows are original sash units, reglazing sash windows before the pelmet goes up saves a second round of disturbance. New glazing units sit in the sash with a warm-edge spacer bar around the perimeter, a polymer or stainless composite strip that replaces the old aluminium spacer and lifts the temperature of the glass edge by a few degrees. That warmer edge is where condensation used to form first, and reducing it directly cuts the moisture load the trickle vent then has to clear.

A deeper reveal after reglazing is common when a slim double-glazed unit replaces single glass in a deep box sash. That change shifts where the blind or track can sit relative to the opening light. Measure the finished reveal depth once the new units are in and the beads are back on. A 24mm sealed unit in a frame built for 4mm glass moves the glass line back and alters the clearance the pelmet needs to the moving sash.

A perfect-fit frame installation sidesteps the pelmet interaction entirely on uPVC windows, clipping a blind directly into the glazing rubber with no screws into the frame. It cannot carry a curtain track or a heavy pelmet, so on a bay wide enough to want a bent track, the perfect-fit route stops at the individual window and the pelmet still governs everything above.

Short alcove returns create a separate problem for the powered side of the track. The motor housing adds about 240mm at one end, and a very short return may leave the end cap doing access work as well as concealment. In that layout, the drawing line may be level while the end of the box still has nowhere clean to hide the drive.