Introduction: Large (4' X 6') Magnetic Whiteboard


I needed a large magnetic whiteboard for my workspace and the commercially available choices are expensive. Also, I wanted to use this opportunity to learn some wood joinery. Specifically half lap joints.

The high level design is as follows:

1) Build a 4' x 6' frame using the 1x4s.

2) Attach galvanized sheet metal to the frame

3) Prime the sheet metal with a white primer

4) Apply the speciality whiteboard paint over the primed sheet metal

5) Hang the whiteboard


1) Measuring tape, framing square

2) Pencil / marker for marking cuts

3) Circular Saw or Table Saw. You will need one with a capability to do beveled cuts.

4) Hammer, Chisel to clean up the shoulders of the half lap joints (if you use the circular saw method)

5) Wood rasp, 80 - 120 grit sand paper (for sanding and smoothing the shoulders of the half lap joints)

6) High density foam roller for the paint (Initiall I used a nylon brush but I was seeing brush marks). I used this roller:

7) You will of course also need the actual roller handle if you don't already have one. I already had one.

8) If you use the Construction Adhesive trade size tube, you will need a caulking gun like this:

9) Drill and driver or screw driver to drive the wafer head screws and also to attach the cleats

10) Level - needed when attaching the cleats onto the wall for hanging the board

11) Thick gloves (yard work nitrile coated gloves work well) for handling the sheet metal. Thinner latex gloves for painting work. I am a messy guy. I need them. :-)

12) Keep a small container of water handy for quick cleanup of paint and also to soak the roller in the water between coats of primer. If you let the primer dry on the roller, you can kiss it goodbye so save it. Rinse and squeeze out the paint a few times and keep it soaked in water while waiting for the primer coats to dry.

13) Assorted weights, bricks, heavy boxes, used milk jugs filled with water etc to weigh down the sheets when glueing


1) Rustoleum Gloss White Dry-erase kit -

2) 2 qty 3' x 4' Galvanized Flashing - about $23 each - from the construction section in HomeDepot - Galvanized Steel sheet metal used for Flashing

3) 5 qty 1" x 4" x 8' These boards are for creating the frame. I used these - at a little less than $4 per board. -

4) Construction glue. I used this: Gorilla Heavy Duty Construction Adhesive -

5) Washer head 1/2" lathe screws. You will find these named as "Washer Head", or "Waferhead", or Modified Truss Head screws. They all are the same. I used these to attach the sheet metal to the frame as well as to reinforce the frame member joints -

6) Zinsser Bulls Eye 1-2-3 White Water-Based Interior/Exterior Primer - you need about 1 quart. You can use any other white primer you already have, like Kilz. This is for priming the sheet metal so make sure that if you are going to use any other primer, it is ok to use under the Rustoleum whiteboard paint -

7) Simple Green degreaser or Isopropyl Alcohol - to clean the sheet metal to prep it for receiving the primer and paint

8) Keep water handy for paint cleanup and cleaning the paint rollers between coats

9 1 qty 1" x 6" x 6'. Optional. This is to build a cleat to hang the board.

You don't need this if you want to use any other method to hang the finished whiteboard i.e. heavy duty picture frame hangers or directly screwed onto studs in the wall -

Step 1: Cuts

1) Cut three (3) 6 foot lengths out of 3 of the 1"x4" boards

2) Cut the other two 1" x 4" boards in half to get four 4 foot pieces. We will use only 3 of them.

These are your basic cuts for the frame. You will create a frame by attaching the 6 foot pieces horizontally as Top, Middle, and Bottom.

The three 4 foot pieces will be the left, center and right vertical pieces to basically form a grid.

Step 2: Joinery Cuts

As I said in the introduction, I wanted to do half lap joinery. I have sketched an example of what this looks like. The above sketch is a left corner joint for the top horizontal piece with the left vertical piece.

Basically you take out half the thickness of the material on each piece, so that when you overlap each piece, they are perfectly flush. Hence half lap.

Now this is where the right tools make a difference. I only had a circular saw and I had seen a technique in which you basically set the blade depth to half the board thickness, and make a number of closely spaced cuts. Then you knock out the small feathered pieces and sand the rough edges down to get as smooth a surface as possible.

If you have a table saw with a "dado" blade, then this is reportedly easier but I have neither. If you are very skilled at making precision cuts you might be able to do this with something like a japanese saw.

Each "Lap" is exactly the width of the board so that when you join then at a right angle, nothing sticks out.

Since a 1"x4" is actually only 0.75" thick and 3.5" wide, set the circular saw depth to 0.37" and mark 3.5" from the ends of the cut pieces.

Setting the circular saw blade to such a precise depth was a bit tricky for me. My circular saw is an old one with not much marking help. Basically it is better to eyeball it and make some sacrificial cuts on scrap pieces of 1 x 4. Remember the extra 4 foot section remaining from the previous cuts? This would be a good use of that!

Once you have set the circular saw blade at the right depth, plan on doing all these feathering cuts all at the same time.

You will need to do these half lap cuts at 12 corners total. All on the same side of the board.

In addition, you will also cut 6 half-lap T joints right in the exact center of each of the boards such that the 1.75" of the lap is on either side of the center line.

Here is a good link which explains half-lap joins:

In the first sketch above, I have a half lap corner joint, and also a half lap T-join cut in the left frame piece.

The subsequent pictures show how I cut many little lines after marking the exact depth and then knocked out the pieces of wood. Sand the surface with some rough grit sandpaper or a rasp.

Step 3: Assemble the Frame

Time to assemble the frame.

First dryfit all the pieces and make sure nothing is out of alignment. All the frame members should be at right angles to each other.

Assemble the frame as seen in the schematic above. Glue the half laps and clamp and optionally screw the frame half lap joints.

The second schematic shows the joins augmented with screws. Make sure that all the screws are all on the same side of the frame. This will be the backside of the frame.

Step 4: Glue the Sheet Metal

Once the joinery glue has dried, it is time to glue the sheet metal.

If you augmented your joints with screws, you will need to flip the frame because the screw heads will not be flush with the frame and the sheet metal will not have good contact with the frame for glue to work.

Follow the directions of the construction adhesive you are using and lay a bead on the frame face and carefully lay the sheet metal.

BE CAREFUL handling the sheet metal. It is quite thin and not very heavy. Consequently it has very sharp edges. Thick gloves would a very good idea. A helper would be even better so that you can lower the sheet metal.

Once both the sheets are attached, clamp the sheet and put on all sorts of weights to on the frame to make sure all the edges of the frame with the glue have good contact with the sheet metal.

Be careful not to topple any weights you use directly on the sheet or in the middle. A dent would pretty much ruin the smooth surface of the sheet and it would be hard to get it out.

Allow the glue to cure. I also used screws from the front on four corners of each sheet so the screw would go through both the wood lap shoulders and do double duty. The wafer heads of the screws sunk on the front are pretty much invisible once they are covered with three layers of thick primer and the thick paint.

Step 5: Attach Hangers to the Backside

Now depending on how you choose to attach the whiteboard to the wall, you have a few options.

In my case, I decided to attach the whiteboard to the wall with cleats.

Cleats are a simple yet extremely reliable mechanism to hang large heavy items.

The frame itself is not very heavy actually. However it is very unwieldy due to its size.

You could use large photo frame hangers or cleats.

Here are the steps if you decide to use cleats.

1) Rip the 1" x 6" board in the middle at a 45 degree angle. A Rip cut means basically cutting along the grain of the wood. Try to center the cut as much as possible. If you have a table saw, then this step is quite easy.

I did it with my circular saw.

2) Now cut these ripped pieces into two 2.5' pieces (two and half foot pieces).

Basically, you should end up with 4 pieces of wood with one edge at a 45 degree angle.

3) Attach a pair of of these ripped pieces to the back of the board along the top edge such that the 45 degree cut is at the bottom, and sloping inwards and upwards towards the front of the board.

4) The other two pieces of the ripped pieces go on the wall and the 45 degree edge is at the top edge, but this time sloping inwards and downwards towards the wall.

5) Now, since you used cleats, and if the cleats are sticking out from the backside of the board, you will need an additional piece or two of 1x4 attached at the bottom of the board so as to even the standoff.

Step 6: Prime and Paint

Now once the glue has dried, and all construction work is over, you are pretty much ready to paint.

It would be a good idea to lightly spray the surface of the sheet metal with alcohol or even Simple Green degreaser and wipe it down. If you do use Simple Green, wipe the sheet faces again with a water dampened rag.

Now apply 2 to 3 coats of the primer as per the primer direction.

I used Zinser Bulls Eye 1-2-3 based on so many testimonials about its coverage etc but I still had to do 3 coats. See the pictures above after the 2nd and 3rd coats of paint.

Give enough time for the primer to dry.

I applied the first coat of the primer with a brush and I was seeing brush marks so I went and bought a dense foam roller and used that for subsequent primer coats as well as the final Rustoleum White board paint.

Finally, mix the Rustoleum white board paint. It comes in a pair of cans. Mix the smaller can into the larger one as per directions and use it all up in one go. Once mixed, the paint is only good for about 1 hour.

It took me less than 15 minutes to paint the board carefully.

Let it cure for at least 3 days.

Step 7: Admire Your Board and Use It!

After waiting for at least 3 days for the whiteboard paint to cure, you can hang up the board on the cleats and start using it.

Now here comes some review of the whiteboard paint itself.

So far I have found that certain colors of the low odor expo markers do leave ghosting on the board pretty much immediately.

I have a set of low odor expo markers I bought from Costco and it has additional colors like pink and orange in it. The orange color seems to leave a lot of ghosting.

Black, blue and green wipe off pretty cleanly. Red needs a little bit of persuasion.

Overall I am very happy with my board.

Best of all, since it has galvanized steel sheet as the base, it is very easy to stick even the weakest of magnets onto it.

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