Most blind installs don’t need spacer blocks. They’re a problem-solving accessory, not a standard requirement, and skipping them when they’re not needed keeps the install cleaner. In a few specific situations, though, they’re the right (and sometimes only) fix.
Shop Custom Window Blinds and Shades
Do blinds actually need spacer blocks?
Usually no. A standard outside-mount install uses the brackets that ship with the blind, screwed directly into the wall or trim above the window. Inside-mount installs work the same way, with brackets seated against the inside of the frame. Most windows have enough clearance to handle the brackets without anything extra.
Spacer blocks (also called extension blocks, bracket extenders, or filler blocks) come in when something on the wall or window gets in the way of where the bracket wants to sit. If your install is going smoothly, leave them in the hardware bag. Extra parts you don’t need create extra play in the system.
When are spacer blocks actually necessary?
Four scenarios cover most of the cases where spacers are the right call.
Outside-mount blinds over deep trim or crown molding. If the window has crown-style trim or thick exterior casing, the bracket can hit the trim and angle forward, making the blind tilt. A spacer behind each bracket levels the install by pushing the bracket out far enough to clear the trim.
Outside-mount blinds with protruding hardware. Casement window cranks, lock latches, alarm sensors, and door handles below an outside-mount blind can all interfere. A spacer moves the bracket forward so the lowered blind clears the hardware without snagging.
Layered window treatments. Installing blinds underneath drapery, or stacking a sheer behind a roller shade, requires moving the inner treatment out so the outer one has clearance to operate. Spacer blocks create that gap cleanly.
Inside mount with shallow frame depth. Less common, but on extra-shallow frames, a spacer can pull the bracket back enough to keep the blind from protruding past the frame. For new construction where window framing is minimal, this is occasionally the difference between an inside mount that works and one that doesn’t.
How do you install spacer blocks correctly?
Hold the spacer against the wall or trim where the bracket will mount, then position the bracket on top of the spacer. Mark the screw holes through both pieces. Pre-drill if you’re mounting into hardwood trim or a stud.
Use screws long enough to pass through the bracket, the spacer, and into the structural material behind by at least an inch. A 3/8-inch spacer calls for screws roughly 3/8 inch longer than those shipped with the bracket. Most spacers come in 3/8-inch and 1/2-inch thicknesses, giving a single block that amount of clearance. Stacked, two can add closer to 3/4 inch.
Always use spacers of identical thickness on both sides. A thicker spacer on one side tilts the blind, throws off the lift mechanism, and shows up as a visible slant when fully lowered. Spacers should also match in material; mixing wood and plastic can lead to uneven compression as humidity changes. Our installation guide walks through bracket placement step by step.
What mistakes do people make with spacer blocks?
Three show up most often.
Using spacers to fix the wrong mount type. If your inside-mount bracket won’t fit because the window depth is too shallow, switching to outside mount usually solves the problem more cleanly than forcing the inside mount with spacers. Spacers handle clearance, not mounting decisions.
Forgetting to switch to longer screws. The screws that ship with the bracket are sized for the bracket alone. Adding a 1/2-inch spacer means the original screws only bite into the spacer, not the wall behind. The bracket may hold for a few weeks, then pull loose under the weight of the blind.
Skipping the valance return adjustment. If your outside-mount blind has a valance with returns (the side pieces that wrap around to the wall), spacers move the headrail out, which leaves a visible gap between the wall and the valance. Order extended valance returns at the time of purchase if you know you’ll be using spacers. For multi-window installs, catching this before ordering saves a return trip.
Do blinds come with spacer blocks?
Depends on the product. Some faux wood blinds and wood blinds ship with one or two spacer blocks included. Others don’t, which is fine for most installs, but means a hardware store run if you discover mid-install that you need them.
If you’re outfitting multiple windows and know in advance that some will need extra clearance, our team at (877) 702-5463 can confirm what hardware ships with your specific blind type before you order. Proper installation also affects how long your blinds last; our How Long Do Custom Blinds Last article covers what to expect.
How do you measure to avoid clearance issues before you order?
Most spacer-block headaches trace back to measurements taken without checking for obstructions. Before ordering, scan the window for anything that protrudes into the bracket’s path: window cranks, lock handles, alarm sensors, and the depth of the trim. Our measuring guide covers each step, including casing thickness on outside mounts. Vertical blinds and other wide-window treatments often need extra attention since the brackets span a larger area.
If anything looks borderline, our experts at (877) 702-5463 can walk through your specific window before you order. Custom blinds and shades ship free across the contiguous United States and Canada, and most ship within 5 to 7 business days. Our Ultimate Guide to Window Treatments is a useful starting point if you’re outfitting an entire home.
Frequently Asked Questions
Spacer blocks create clearance between the wall and the mounting bracket. Most often, they’re used on outside-mount installs where window trim, crown molding, window cranks, or other hardware would prevent the bracket from sitting flush against the wall.
Close but not identical. Spacer blocks sit behind the standard bracket and push it forward in small increments (usually 3/8 inch). Extension brackets replace the standard bracket and project the headrail farther from the wall, often several inches. Use spacers for small clearance issues, extension brackets for larger projections.
In most cases, yes. Standard inside-mount and outside-mount installs use only the brackets that come with the blind. Spacer blocks are an add-on for specific clearance problems, not a universal install requirement.
Standard spacer blocks come in 3/8-inch and 1/2-inch thicknesses. One 3/8-inch spacer per bracket clears most trim and hardware obstructions. Two stacked spacers (about 3/4 inch) handle deeper trim or thicker hardware.
Yes, though factory spacers are inexpensive and sized for the screws and brackets that come with blinds. If you make your own, cut both spacers from the same material to the same thickness, and check that the screws you use are long enough to pass through the bracket, the spacer, and into the wall by at least an inch.
No. Spacer blocks are a standard install accessory and don’t affect product warranty. Our warranty (3-year limited, with a free upgrade to 5 years on Blindsgalore products) covers original defects in materials and workmanship when the blind is properly installed.