DIY CAT SHELF / Plant Shelf / Window Sill Shelf Extension (Give Cats And Plants A Place To Sit!)

DIY CAT SHELF / Plant Shelf / Window Sill Shelf Extension (Give Cats And Plants A Place To Sit!)

Makita 7-1/4″ Circular Saw:
Bosch 12 amp Router:
Dewalt 18ga Brad Nailer:
Porter Cable Compressor:
Swanson Speed Square:

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Here’s a link for the “Trim Rot Repair” video mentioned above:

A window sill shelf gives you more room for plants and decorations–and, of course, cats! This short video from The Honest Carpenter will show you how to build and install your own window sill shelf extension with a minimum of material and labor. This is a perfect cat shelf / plant shelf! Give your cat a place to perch 🙂

Typical window sills (or “stools”) are only 3-5″ deep. This window sill shelf extension is 9″ deep, about the depth of your average book shelf.

Tool List:
Tape Measure
Circular Saw OR Jigsaw Or Coping Saw
Router (optional)

Material List:
1×10 pre-primed pine
3″ screws
Liquid Nails

Cat Shelf / Plant Shelf / Window Sill Shelf Extension How-To:

1) Measure existing window sill. Add 1″ to each end for overhang.
2) Mark center of existing sill
3) Cut pre-prime stock to desired measurement with circular saw or jig saw.
4) Mark center of window sill shelf extension piece.
5) Bring piece inside and mark notches for mullions or separations.
6) Measure depth of window bays. Note measurements on board.
7) Plot and cut notches for mullions and separations.
8) If necessary, cut out lower ends of window side casings
9) Slide window sill shelf extension into place. If necessary, cut to make piece fit more tightly.
10) Spread liquid nails in zig-zag pattern on existing window sill. Press new window sill shelf firmly down into place.
11) Pre-drill and countersink screw locations at center of window bays. Drive screws through window sill shelf and original sill, into rough opening framing.
12) Tape, caulk, prime and paint
13) Introduce your cats to the cat shelf / plants to the plant shelf!

That’s how you build a window sill cat shelf / plant shelf extension! If you have any questions, feel free to put them down in the comments section.

Be sure to visit us at The Honest Carpenter website:


  1. Snow W on May 12, 2021 at 1:07 am

    I am installing new window, there is no existing sill in place,. Do you think I can skip the 6” sill and use 10” directly or it is better to stack them?

  2. Ray Gallagher on May 12, 2021 at 1:09 am

    how wonderful! i should do this for the twin double hungs in my office !

  3. Felicia Felicia on May 12, 2021 at 1:10 am

    My plants will love you for this!.

  4. Tran The Clever on May 12, 2021 at 1:13 am

    I’ve never seen a floating shelf made this way, I love it! Thank you for all the woodworking tips, great for beginners like me. 4:59

  5. R B on May 12, 2021 at 1:13 am

    how do you know the sill you installed can hold the weight of the plants, cats, etc. ?

  6. preeview9 on May 12, 2021 at 1:14 am

    Thanks for this! I’m curious if you have suggestions about how to support these without using adhesive, so that they’re removable down the line if I were to want to restore my original wood sills. Would you recommend removing the existing sills and replacing them completely? Would installing some kind of wood bracket support be a good idea in this case?

  7. David Wade on May 12, 2021 at 1:14 am

    You are awesome! I am binge watching your videos. Thank you for all the great tips and tutorials.

  8. Bill Randall on May 12, 2021 at 1:15 am

    OMG> I need to hire someone to do this! Sacramento.

  9. Scott R on May 12, 2021 at 1:16 am

    Great video and idea. i recently bought one of these Makita magnesium circular saws. If you think about it, next time you make a video using the rip guide, could you go into detail on how that is used and installed. Happy father’s Day

  10. Vince Mucci on May 12, 2021 at 1:16 am

    Wanted to do this in my kitchen, going to be Tricky since i have Andersen windows with handle controls

  11. Gabriel McAteer on May 12, 2021 at 1:20 am

    Thank you for the video! What would you suggest if the original sill that you want to cover is marble?

  12. Feline Jungle on May 12, 2021 at 1:23 am

    Great idea! for cat and plant lovers like me!

  13. Bill Zardus on May 12, 2021 at 1:24 am

    Cal me crazy but I would have included the words "catwalk" and/or "cat" in the video name
    so more people could find this video via the Youtube search engine. You have to search for the
    video yourself via the search engine to see how easy it is to find. It is MUCH better to have too many
    keywords in the video name than too few.

  14. Maxima on May 12, 2021 at 1:26 am

    Luv this. Fyi your mic volume is recording low

  15. Jonathan Posey on May 12, 2021 at 1:27 am

    Excellent tutorial!

  16. Luna Danu on May 12, 2021 at 1:28 am

    just the guide i was looking for, thank you

  17. aztcsoul on May 12, 2021 at 1:32 am

    What about adding a window sill to one that doesn’t have one?

  18. Sharon Zapotocky on May 12, 2021 at 1:32 am

    Great project! Well explained.

  19. W. A.Z. on May 12, 2021 at 1:32 am

    Beautiful work! Do you think this principle would work to extend the top of an old built-in corner tv cabinet? I want to make my slightly wider flat screen fit rather than tear down the built ins or use up floor space with another tv stand or make holes on the wall for a wall mount swing arm. I’m imagining something like a mantel that would extend the front of the cabinet top just enough for the base of my tv to sit on and quasi "float" in front of the cabinet shelves. Thanks for any suggestions!

  20. K H on May 12, 2021 at 1:35 am

    Really good video! Thanks!

  21. Kimberlee Rivera on May 12, 2021 at 1:35 am

    What a big difference a wider window sill makes – beautiful!
    That looks classy! Thank you!

  22. Roy Smith on May 12, 2021 at 1:36 am

    Very low volume

  23. Brian Krueger on May 12, 2021 at 1:36 am

    Very nice.

  24. Home and Garden DIY on May 12, 2021 at 1:37 am

    What do you suggest when it is clear that an existing window sill tips downward from the outside edge in toward the bottom of the window? Should that old still be removed, or can something be used to shim (I doubt that’s the right word) the inside edge of the window sill before the new still is added? Thank you in advance for your help!

  25. bel cascabel on May 12, 2021 at 1:37 am

    Hey! Really cool video! I want to make this project with my windows too but don’t know how to finish the wood’s surface. Do you have a video on that?

  26. Enrique on May 12, 2021 at 1:39 am

    Brilliant!!!, thank you

  27. Bijoux W on May 12, 2021 at 1:39 am

    Thanks for the great video. I want to make an extended sill for my plants in a bathroom and still be able to lower & close my blinds, so this helpful.

  28. Jane Tang on May 12, 2021 at 1:47 am

    This video is so helpful ! Thanks So much!!!

  29. Snow W on May 12, 2021 at 1:47 am

    Is it safe to stand on the extension?

  30. Jamie Spruce on May 12, 2021 at 1:50 am

    Excellent video!

  31. Gaia Carney on May 12, 2021 at 1:51 am

    Great idea, Honest Carpenter 💛Thanks for creating & sharing this video

  32. Cassaundra Spann - 2QSBAAB on May 12, 2021 at 1:55 am

    Great job!! Love this! It seems as if you have trim underneath the window sill, did you remove them before adding the extension?

  33. Dave Dube on May 12, 2021 at 1:55 am

    Nicely done!

  34. John McDermott on May 12, 2021 at 1:56 am

    Why do you leave the old stool in? I am getting ready to replace two that my dog chewed the corners of and I. Was just curious why you would not remove the old one first.

  35. Lou Indorato on May 12, 2021 at 1:56 am

    Turn up the volume lol

  36. Susan Evans on May 12, 2021 at 2:00 am

    Do you have any ideas for apartment dwellers for a removable shelf?

  37. Samuel Douglas on May 12, 2021 at 2:00 am

    You made this look easy enough for me to try, and I’ve always wanted deeper windowsills for my cats. I have a problem, though. From the top of my existing window sill to the edge of the window opening is only 7/16ths of an inch. What kind of wood could I use?

  38. Ameer A on May 12, 2021 at 2:00 am

    Excellent guide. My wife is going to be thrilled when she can return all of her recently repotted plants to the window. Thank you.

  39. Freaky Playz on May 12, 2021 at 2:01 am


  40. Ed Over50 on May 12, 2021 at 2:03 am

    Nice work Ethan. Keep the videos coming

  41. Franklin Sosa on May 12, 2021 at 2:03 am

    I watch every video 👍🏻

  42. Devyn Barnard on May 12, 2021 at 2:04 am

    You didn’t remove the previous window sill?

  43. Katie Ackerman on May 12, 2021 at 2:04 am

    Thanks for this! Really nice to watch and should help me with a triple window "sill" I’m doing. Using reclaimed doug fir and need to route out the part on the sill so it will sit under my window cranks, so that’s the real bear, but I really appreciate your middle marker tip–hopefully it goes well!

  44. Ginger Lauderback on May 12, 2021 at 2:05 am

    Our windows don’t have side casings, but we would like to add them. I found this video while searching for a way to extend the sill left and right since it’s currently too short for side casings. I think this would work, but I’m wondering if there is a way to also cover the old sill so it doesn’t show from the front (some of our windows are higher and it would be obvious there are two sills). Thanks! 🙂

  45. Anis Azziyati Juhari on May 12, 2021 at 2:05 am

    very well explanation & demo!

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