Blackout Roller Shades With Side Tracks: When You Need Them

Quick Answer: Blackout roller shades with side tracks pair a blackout fabric with U-shaped channels mounted along each side of the window, so the fabric edges run inside the track instead of leaving a gap. Standard inside-mount blackout shades usually leave roughly 5/8 to 11/16 inch of open space on each side, and that sliver is where most morning light gets in. You need side tracks when you want near-complete darkness for sleep, a nursery or a media room; for most other rooms, an outside mount or slim light blocker strips are enough.

This guide explains where light gaps come from, how side channels work, how they compare with cheaper fixes, and how to plan motorized blackout roller shades so the whole window, not just the fabric, goes dark.

Why Do Blackout Roller Shades Still Let Light In?

Blackout fabric blocks essentially all the light that hits it. The problem is the light that never hits it. A roller shade has to spin freely, so the fabric is made narrower than the window opening to keep it from rubbing against the window frame. On an inside mount, that clearance typically adds up to about 5/8 to 11/16 inch on each side. Add a small gap above the roll and a gap at the sill, and a "blackout" shade can still leave bright lines around the edges at 6 a.m.

How much that matters depends on the room:

• Bedrooms for light sleepers and shift workers: edge glow is often enough to wake you, and restful sleep is the whole point of the shade.
• Nurseries: daytime naps need the darkest possible room.
• Media room or home theater: stray light washes out a projector screen and causes glare on a TV.
• Living rooms and kitchens: light gaps rarely matter; a light filtering fabric is usually a better fit anyway.

How Do Side Tracks for Blackout Shades Work?

Side tracks (also called side channels or U channels) are narrow rails fixed to each side of the window opening. The edge of the shade fabric travels up and down inside the channel, so there is no straight path for light to slip past it. Commercial shade makers offer several profiles, including the U channel, the H channel for joining two shades, and the L angle that covers a gap from the front.

What Weffort side rail tracks add

The Weffort side rail tracks for blackout shades use a U-shaped profile made from powder-coated aluminum, with fiber brushes inside the channel that close the remaining space around the fabric while still letting the shade move. They can be fixed with adhesive nano tape on smooth, even surfaces or with screws on rough or uneven surfaces. Two cautions from the product notes: the adhesive cannot be reused once removed, and stucco surfaces are not recommended.

Side Tracks vs Other Ways to Reduce Light Gaps

Side channels are the most effective fix, but not the only one. Here is how the common options compare for blackout roller shades.

Method	How it blocks light	Light blockage at edges	Best for	Trade-offs
Side tracks (U channel)	Fabric edges run inside a channel	Highest	Bedrooms, nurseries, media rooms	Most visible hardware; needs flat, square jambs
Light blocker strips (L angle)	Strip covers the side gap from the front or behind	High	Inside mounts, renters, retrofits	Does not seal top or bottom
Outside mount with overlap	Shade is wider than the window opening	Good	Shallow frames, any room	Some light at the top and around the trim
Blackout curtains or drapes layered over the shade	Fabric panels cover the edges and frame	Good to high	Bedrooms that want a softer look	Bulk; another layer to open and close

Weffort also sells L-shaped light blockers made from durable polystyrene. They sit in front of or behind the shade, can be trimmed to your window height with utility scissors or tin snips, and install with nano tape or screws, so they suit an existing inside-mount shade where full channels would be overkill.

When an outside mount is enough

Mounting the shade on the wall or trim above the window and making it wider than the opening is the simplest way to reduce light gaps. As a rule of thumb, overlap the opening by at least 2 to 3 inches per side and mount 3 to 4 inches above it. That gets most rooms to "dark enough" without any tracks, and it also works when the window frame is too shallow for an inside mount. For a deeper comparison, read inside vs outside mount for maximum blackout.

Benefits Beyond Darkness

• Privacy: sealed edges mean no sightline around the shade, which matters on street-facing bedrooms.
• Energy efficiency: closing the gaps reduces the air movement between the glass and the room, so the shade acts more like an insulation layer in winter and blocks more solar heat in summer. The gain is real but modest; do not expect it to replace better windows.
• A cleaner look on wide shades: channels keep the fabric from swaying and give the edges a finished line.
• Less noise from flapping fabric near an open window or a vent.

Measuring and Installing Shades With Side Tracks

Side tracks raise the stakes on measuring, because the fabric now has to line up with a fixed channel on both sides. Follow the full steps in how to measure roller shades, then run through these checks:

1. Measure width at the top, middle and bottom of the window opening. If they differ by more than about 1/4 inch, the frame is out of square and tracks may bind; consider light blockers or an outside mount instead.
2. Measure height on the left, middle and right. Note the length each track must cover.
3. Do not make your own deductions. Give exact opening sizes and let the order process handle clearances.
4. Check depth. The headrail plus the tracks must fit in front of the glass, window cranks and locks.
5. Check the jamb surface. Smooth painted wood or vinyl suits tape; textured or uneven surfaces need screws; skip stucco.

Installation is a DIY job for most people: mount the shade first, lower it fully, then attach each track so the fabric runs centered in the channel with no rubbing. Run the shade up and down several times before the adhesive fully cures or before driving the final screws. If you prefer a tool free installation for an existing shade, adhesive light blockers are the simpler choice than drilled channels.

How to Choose Blackout Roller Shades for Complete Darkness

Start with the room goal, then pick fabric, mount and edge control together:

Goal	Fabric	Mount	Edge control
Pitch-dark bedroom or nursery	Blackout	Inside	Side rail tracks
Dark bedroom, simple install	Blackout	Outside, 2–3 in overlap	Optional light blockers
Media room with a projector	Blackout in a darker color	Inside	Side rail tracks
Rental or existing shade	Keep current blackout shade	As installed	Light blockers

For fabric, the Signature Dark Series motorized blackout roller shades come in deep colors such as Anchor Grey, Umber and Charcoal, which suit media rooms where a pale shade would read as a bright rectangle. Motorization is worth adding here: scheduled shades can close at bedtime and open gradually in the morning, and you never have to tug fabric that is running in a channel. Our motorized roller shades buying guide covers power and smart home options. If you also want a sheer daytime layer in the bedroom, compare dual shades for the bedroom. For blackout on a patio door, see roller shades for sliding glass doors.

Frequently Asked Questions

Can roller shades be blackout?

Yes. A roller shade with blackout fabric blocks essentially all light through the material. To make the room itself dark, you also have to deal with the gaps at the sides, top and bottom, using side tracks, light blockers or an outside mount.

How much of a gap is normal for blinds and shades?

For an inside mount, expect roughly 5/8 to 11/16 inch per side on a standard blackout roller shade. That clearance lets the fabric roll without rubbing the frame and is normal, not a defect.

Can side tracks be added to existing blackout shades?

Often, yes, if the fabric width lines up with where the channels can be mounted and the window frame is square. If the gap is uneven or the jambs are irregular, L-shaped light blockers are the easier retrofit.

Do side tracks completely eliminate light?

They remove most of the side light, which is usually the largest leak. Some light can still come from the top of the roll or the sill, so mount carefully and consider an outside mount header or top cover if you need complete darkness.

What are the best room darkening blinds for sleep?

For sleep, choose a true blackout fabric rather than room darkening, then control the edges. A blackout roller shade with side tracks gives the darkest result; a blackout shade on an outside mount is a close second with a simpler install.

Get a Darker Room

Ready to fix those bright edges? Browse Weffort blackout roller shades, size them for your window, and add side rail tracks where you need full darkness. Order free fabric samples to check color and opacity against your own window first.