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Magic Castle

Mr. McGroovy’s Cardboard Castle Plans illustrate simple, easy techniques for building a cardboard castle playhouse using Mr. McGroovy’s Box Rivets™ and your own large boxes.

View castles people have made >>

Learn about castle painting options >>
Learn to paint the realistic castle texture >>

Approximate size if built with…

  • Refrigerator boxes = 10′ x 10′
  • Washer/dryer boxes = 10′ x 10′
  • Wardrobe boxes = 8′ x 8′
  • Dishpack boxes = 5′ x 5′ (toddler sized!)


Boxes NOT included. See How to Get Free boxes.

How do you paint that cool brick pattern on the castle?

Believe it or not, the brick design is really easy to paint (anyone can do it)!

For an overview of painting your cardboard project, read my Instructions
or What are different ways to paint the castle?

Follow the instructions below to find out how to paint realistic castle texture.

1. Paint a base coat

base coatPlan for about one gallon of paint for eight refrigerator boxes.If you use a paint sponge instead of a roller or paint brush it takes less time and you will use less paint.

You will also need one quart of white paint and one quart of black to use for the highlights and shadows. You will have plenty of black and white left over for other projects.

2. Draw out the brick pattern.

I used a fat Sharpie I purchased at the hardware store. I used a measuring stick to mark out the bricks, but don’t make them too perfect or it won’t look right either.

Fat SharpiePainting Brick Lines

3. Round the brick corners.

Just put a little mark at each corner to make the bricks look rounded.

Painting BricksPainting Bricks

4. Draw the arched windows and doors

I first traced the outline of my window (or door) and then drew in the bricks around the outline. I did this before marking out the other horizontal brick rows.

Arch PaintingArch PaintingArch PaintingArch Painting

5. Texture the bricks

To make the texture on the bricks, I used a “dry brush” technique that I learned while painting theatrical sets. Basically, get a little paint on your brush and then paint it out on another surface, so that your brush is “dry”.

Dry Brush PaintingDry Brush Painting

6. Paint the brick shadow

Use the dry brush technique to paint a black line along the bottom of each row of bricks (just above the horizontal lines), and then on the left hand side of each brick (right side of the vertical lines). I also added a shadow to the arch bricks.

Texture PaintingTexture Painting

Using a curved brush stroke, round out each brick by making a curved transition from the horizontal shadow line to the vertical shadow line.

Texture PaintingTexture Painting

Put a little texture in the middle of the brick by just dabbing a few spots.

Add a little heavier shadow around the window ledge.

Texture PaintingTexture Painting

7. Paint the brick highlight

Use the dry brush technique to paint a white line along the top of each row of bricks (just below the horizontal lines), and then on the right hand side of each brick (left side of the vertical lines). Add the curving corner as well.

Texture PaintingTexture Painting

And that’s it!

Good luck and enjoy your castle!

Castle Tower Painting


Collecting Boxes

Mr. McGroovy’s Project Plans™ can be built using different types of boxes. Most builders use refrigerator boxes, washer/dryer boxes, wardrobe boxes or dishpack boxes. These boxes all have similar height-to-width proportions. To illustrate step-by-step building instructions, the plans show refrigerator and washer/dryer boxes of average size, but different sized boxes can be substituted. For example, build a cardboard castle with eight dishpack boxes instead of eight refrigerator boxes for a toddler sized playhouse that fits in the living room

Standard Box Dimensions



Kraft Paper Tape can be used to fix the flaps on wardrobe, dishpack and moving boxes. Kraft paper tape has a paper binding, and takes paint better than any other kind of tape

Kraft Tape Modifications


Boxes Do NOT Have to be the Same Size

Boxes you collect will likely not all be the same size, and Mr. McGroovy’s Project Plans™ can be built using different sized boxes. When using Mr. McGroovy’s Box Rivets™ to assemble your project,it is easy to adjust flaps and connections to accommodate differently sized boxes.

Connect Different Sized Boxes


How to Get Free Boxes

Don’t waste your time going to Home Depot/Lowe’s/Sears/Best Buy/etc. Large chain store retailers won’t give you any boxes. But you do have to call them. Ask for the “appliances” or “delivery” department and say,

“Hi, I sure hope you can help me. I know your store doesn’t give away refrigerator boxes, but I was told that the local delivery company that works for you does. Can I have their name and phone number?”

The part-time, high school student who works evenings and weekends will probably give you the 800 number for GE. That’s the hotline he or she calls to schedule deliveries. So call back during regular business hours when the full-time person is there, and ask specifically for the name and number of their local delivery contractor. You may have to call several times at different times of the day until you get someone knowledgeable…but it’s worth it! Local delivery contractors can have as many as 30-60 boxes a day.


A Note About Refrigerators Shipped in Bags

Many refrigerators are now coming shipped in plastic bags (BOO!), which reduce shipping damage. This is mainly for the largest refrigerator models (the most expensive fridges), but it depends on the manufacturer. I’d highly recommend also asking for washer/dryer boxes. These are generally the same as refrigerator boxes, but a little shorter, and a lot more plentiful. Apparently, washers & dryers have to be replaced more often than refrigerators. Washer/dryer boxes can be substituted for refrigerator boxes in all Mr. McGroovy’s Project Plans™, with little difference to your final results.


How to Fit 8 Refrigerator Boxes in Your Vehicle

Take your own utility knife so you can cut off the tops & bottoms of the box. Then refrigerator boxes can be folded as shown and they will more easily fit into your vehicle. Most of my plans assume each refrigerator or washer/dryer box will be in this configuration (i.e. top and bottom flaps cut off).

Fit 8 Refrigerator Boxes in Your Car

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How to Use Mr. McGroovy’s Box Rivets™

Box Rivet Building is a *SNAP*

How Box Rivets Work

Box Rivet Instructions


Choosing Rivet Size

Mr. McGroovy’s Box Rivets™ come in two sizes: single-wall and double-wall.

Single-Wall Rivet Size

The single-wall rivet size works on normal sized cardboard, called “C-flute”. Moving boxes, dishpack boxes, some washer/dryer boxes, and even small refrigerator boxes are made from C-flute cardboard.

Single-Wall Rivet Dimension

Double-Wall Rivet Size

The double-wall rivets works on thick, two-layered cardboard, called “double-wall” of course. Wardrobe boxes, some washer/dryer boxes, and larger refrigerator boxes are made from double-wall cardboard.

Double-Wall Rivet Size


nail punch

Holes Making Method

My preferred method for making holes in cardboard is to use a standard nail punch (without the hammer). It’s easy to just hold it in your hand and poke it through. It’s tough but not too sharp, and leaves a nice 1/4″ hole.



Pull, don't pryMr. McGroovy’s Box Rivets™ are Reusable!

An adult can usually slide their hands between connected layers, give a quick tug, and box rivets pop apart without breaking.

Occasionally you will come across a stubborn rivet, which can easily be removed with a common hammer (pull, don’t pry).

  • Store your project for another day
  • Have a party at the park
  • Donate your project to your school, church or library
  • Build a new project next week, next month, or next year

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Building Techniques

Understanding Flute Orientation

What gives cardboard its strength are the wavy ridges, called the flute, sandwiched between two outer linings. The flute runs in one direction, and the characteristics of working with cardboard differ depending on if you are working with, or against the flute. For example, it’s very easy to cut and fold with the flute. It’s more difficulty to cut and fold against the flute. For steps where flute orientation is important, Mr. McGroovy’s Project Plans™ use these icons:

Flute Orientation


How Many Rivets to Use

How many rivets you need to build a projectdepends on what size boxes you are using, how many kids will be playing in your project, and how long you want it to last. A project for a summer library program requires more rivets than building the same project for a weekend birthday party.

In general, place rivets every 12”-24”. Using more rivets, closer together, makes projects stronger & last longer.

Placement of Rivets


Connecting the Inside Rivet

Placing the inside rivet piece can be tricky because you have to stick your hand inside the box in order to push the two rivet pieces together (if you don’t understand what I mean, you will). To solve this problem, cut a window or door close to where you want to place the rivet, so that your arm can reach inside the box. Another way is to make a small “horseshoe” cut close to the location where the rivet will go. This becomes a small flap that can then be closed up without looking too conspicuous.

Horse shoe cuts


Don’t Measure (Seriously, don’t measure!)

Mr. McGroovy’s Project Plans™ are specifically designed to guesstimate dimensions without measuring, so projects come together quickly.

RELATIVE DIMENSIONS Mr. McGroovy’s Project Plans™ use relative dimensions that show the general size and shape of features to draw, cut or score, relative to the edges of your uniquely sized boxes. Absolute dimensions would not correspond to your collection of uniquely sized cardboard boxes.

VARIABLE DIMENSIONS Occasionally, the dimension of one box will have to match the dimension of another box. A variable (X, Y or Z) is used to show that these two boxes should be cut to the same dimension.

A WARNING TO PERFECTIONISTS: Being a perfectionist takes a lot of time when it comes to building large cardboard projects. If you want to measure each cut to the perfect dimension and make each line perfectly straight, plan to spend every night for two weeks out in the garage. However, it’s just really cool to have a giant cardboard play fort in the backyard. A perfectly built project can have a higher initial “Wow!” factor (to other adults), but ultimately makes little difference to the fun and joy kids will experience when playing in their cardboard fort. Find a balance between your own expectations for how the finished project will look , and how long you want to spend building it.



Utility KnifeUse a utility knife to cut your cardboard boxes. I recommend the inexpensive, disposable model shown here. I own many fancy, expensive utility knives and this is the one I keep reaching for. The blade is securely fastened into the knife – unlike knives with “replaceable” blades. Do not underestimate the labor saved by a sharp knife. Building your project will be an easier experience, and your project will look nicer without all the tears your old knife is going to make. When your knife starts to get dull, just snap off the break-away tip and it’s a fresh blade.

When cutting against the flute, cut three times: once to cut the outer lining, once to cut through the flute, and once to cut through the inner lining. When cutting with the flute, cut twice to cleanly cut through all layers.



You need a dull pencil to mark you boxes when building your project. Pencil marks are easily covered by paint, but a sharp lead can unnecessarily puncture the outer lining of the cardboard.



It is difficult to fold cardboard against the flute. Folding cardboard with the flute is much easier, but it often folds in undesired places. Making a slight indentation along the desired line helps to more easily and accurately fold cardboard. To score the cardboard, run a smooth, round object along the line you want to fold, while applying a small amount of pressure. You do not have to press hard, just enough to make a mark. This technique works well with, and against, the direction of the flute. I recommend using the end of your utility knife. It’s smooth, round, and conveniently located.



Once you have scored a line, place the edge of your hand next to the scored line, and use your other hand to fold the cardboard over in the direction of your fold. The cardboard will crease along the scored line.

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Paint & Decoration

Involve the Kids!

Painting the project is one of the best ways for kids to have ownership of their cardboard play fort. Kids want to have ownership, but it is difficult to involve them in the actual assembly/building of the project. Involving kids in painting the project is one of the best ways to provide kids with ownership, and reduce the time required to complete it. Painting the project yourself can take as long (or longer) as it did to build it.


Printed Box Markings

Some people prefer to completely cover the printed box markings so they don’t show through the paint. The best option to achieve this is to cover markings with a brown spray paint prior to painting your base coat. This step takes additional time and money. I personally do not find it to be worth it. After only one coat of paint, box markings are not visually intrusive, and can subliminally emphasize that this cool thing is built from recycled boxes!


Catch Drips & Spills

Choose a paint surface to accommodate paint drips and possibly spills. The yard/grass works well for this, as paint is no longer noticeable after a week or so. If you build your project on the patio, basement floor, community room, or other area, purchase an inexpensive plastic tarp to place under the project before you start to build.


Use Acrylic or Latex Exterior House Paint

The best paint to use is regular house paint like you buy at the hardware store. The quality of paint is irrelevant, so buy the cheapest you can find. Some discount stores have generic brands for as little as $9/gallon. Ask if they have returned or mismatched paint – usually 50% off. Both acrylic and latex paint are water based so cleanup is very easy, and come in various finishes like gloss, semi-gloss and matte. Latex paint is rubbery when dry and is a better protective layer that can repel water and make for easy clean-up of birthday cake frosting and sticky ice cream fingers.


Paint PadUse a Paint Pad

Paint pads are very easy for kids to use. Using a paint pad allows you to quickly add a thin coat of paint that will minimize warping, and dries in about five minutes. For painting trim, use a smaller paint pad.



Paint First or Assemble First?

There’s no right answer for this one, and it’s kind of a tricky question. It depends on what you are building and what technique you are using to decorate it. If you are going to paint your whole project with a base color, then it’s easier to do this prior to cutting up all the boxes and assembling your project. If you use a paint pad as described above, the paint dries very quickly and boxes can be painted and assembled all in the same session. If you are applying a pattern or decoration using a mini paint roller, markers or some other special tool, then you will want to do this after the project is assembled. That way the pattern will flow nicely from one box to the next. This is difficult to do without first assembling your project.


Painted CastlePainting Your Cardboard Castle

What are different ways to paint the castle?

How do you paint that cool brick pattern on the castle?


How to Paint Wood Grain

How to paint wood grain

1. Paint (mostly) straight lines to indicate the edge of boards.

2. Paint one curvy wood grain line for each board.

3. Add a few (mostly) round circles for knots.

4. Fill in the rest of the wood grain following the first grain line and avoiding knots.

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