What wood is best for a window box?

Cedar or redwood resist rot. PVC trim board and polyethylene boxes never rot and hold paint well.

How far below the window should it sit?

About 2–3 inches below the sill so water and soil don't splash the sill and the window can still open.

Can I mount on vinyl siding or brick?

Yes. On vinyl, drill oversized clearance holes so the siding can move, and seal screws. On brick, use masonry anchors in a hammer-drilled hole.

How to Build and Install Window Flower Boxes: Kit, Steps & Videos

Window flower boxes, built to last.

The short answerTo install window flower boxes, pick a box as wide as the window trim (or build one from cedar or PVC with drainage holes every 6–8 inches). Mount it 2–3 inches below the sill on two sturdy brackets screwed into studs, adding a third bracket for boxes over 48 inches. Fill with moisture-control potting mix and plant thrillers, fillers and spillers. A self-watering box cuts watering in summer heat.

Few weekend projects add as much curb appeal. The details that matter: width that matches the window, secure brackets into framing, and drainage so the box doesn't rot or drown the plants.

DifficultyEasy–Moderate

Time2–4 hrsper window, store-bought box

DIY cost$115–$155estimate

Hiring a proVaries by areaestimate

DIY range is the Home Depot price of the parts below as of Oct 15, 2026 (one 36-in. box, two brackets and soil). We didn't find a reliable published pro rate, so none is shown.

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Tick items off as you shop. Ratings and review counts were checked on 2026-10-15. Home Depot prices are as of 2026-10-15. Amazon shows its price at checkout.