Intro: Giant Mushrooms
I built these mushrooms originally for my annual Halloween haunted yard. They can be used in a variety of ways though - for Alice in Wonderland themes, Dr. Suess themes, weddings, theater, festivals, garden parties and more. These giant mushrooms range in size from 5ft tall to 10ft tall. They are made using wood, chicken wire, cheesecloth, 2-part spray foam, paint and spandex.
Step 1: Building the Stem
lag screws and washers
The top and bottom of the stems are made from 3/4" plywood. Using a jigsaw, I cut them into circles that are roughly 18" in diameter. The center of the stems are made with (3) 2x4s that will change in length depending on the desired height. At first, I had a 1x2 in the center but I don't think it was necessary at all. What IS necessary is using lag screws and washers to connect the 2x4s to the bases.
The lag screws are roughly 3/8" in diameter and 4-5 inches in length. The washers are very important and should match the diameter of the screws. We used a nut driver to tighten the screws. Make sure you pre-drill your holes.
Once the stem is secure, you then wrap them in 1-inch chicken wire from top to bottom using steel wire snips and a staple gun.
To prepare for foam, everything must have a skin for the foam to adhere to. This can be accomplished using cheesecloth or scrim. Cheesecloth can be rather expensive so I buy scrim in bulk by the yard from Online Fabric Store. https://www.onlinefabricstore.net/natural-cotton-scrim-fabric-.htm
I simply adhere the scrim to the chicken wire using spray adhesive. It is important to work outside and use a face mask while spraying adhesive. Once finished, you can move onto the foam.
Step 2: Building the Cap
The cap skeleton consists of the following:
3/4" Electrical Conduit
3/4" poly flex tubing (found in plumbing and pvc)
4x4 lumber cut to 1ft length.
1/2 " or 3/4" plywood
The cap and stem are meant to be detachable to make for easy transport and storage. First create a stem and base for the cap itself. Cut an 18" circle out of the plywood and then cut the 4x4 into a 1 foot section. Use lag screws and a washer to attach the two. The tricky part was figuring out where to pre-drill holes for the conduit to go through. Using a 1" spade bit, drill your holes through the 4x4 for the conduit to pass through. Once you have your conduit through the holes in the center stem, you can start bending. Think of creating an umbrella shape with curves. The bends are subject to your own creative desires.
Once your conduit is bent and centered, wrap your pvc tubing around the perimeter egde. Pre-drill holes where it will attach to the conduit and then simply screw the conduit to the pvc tubing uisng screws, washers and nylon lock nuts.
Take your chicken wire (the wider the better) and lay it over top of the cap structure. Cut around edges and wrap excess under tubing. Attach with zip ties.
Attach scrim to chicken wire in the same manner as the stem.
Step 3: Foaming and Painting the Mushroom
I used a closed cell spray foam system from Versi Foam. This is the System 50 kit. It comes in 2 tanks and it is magical. With shipping, this system costs a little under $800. To learn more about Versi Foam, visit http://www.rhhfoamsystems.com/.
Follow instructions. Take all precautions. Be safe. This stuff is not to be messed with. Make sure you have all your safety gear including a suit, mask, goggles and gloves.
Once tanks are ready and you are protected, start spraying. The foam cures very quickly. I do 2 coats for added strength.
Once foam is completely cured, i then paint using a sprayer. Once paint is dry, attach cap to stem to prepare for the gills. This is a good time to add l.e.d. lighting or string lights. You can attach lighting to the underside of the chicken wire using zip ties.
Step 4: Creating the Gills
This is the most tedious part of the build as it involves lots of pleating, stapling, velcro and hot glue.
I start by buying 10 yards of 120" white nylon spandex from www.spandexhouse.com. 10 yards should yield enough for a few mushrooms depending on their size.
In my original build I was stapling the spandex to the center cap and then hot gluing directly to the outer edge but I have since added Velcro so i can remove the spandex when not in use. You can buy Velcro by the roll in 1" strips. First i cut different lengths and stick to the outer top edge of the cap base. Then stick the strips to the entire perimeter of the outer edge.
Starting the pleat is tricky but think of using spandex in the form of triangles. I don't pre-cut these because if you make a mistake and the spandex doesn't reach far enough, you have wasted fabric. So I start by cutting a flat edge on the spandex, roughly 24" and then adhere that to the Velcro that was applied to the outer top edge of the cap base. I then pull the spandex out to the outer edge of the cap and start pinning to find my way through the pleat. This pleat will change as you start to permanently adhere but the pinning is necessary so you can get the correct drape.
Once done pinning, cut above the pin. Fold the rough cut part of the spandex over so it makes a clean edge and hot glue to the Velcro.
Once you have the first section of fabric done, move on to the next and so forth. I hot glue the fabric seams together and leave some open to get inside for light repair if needed.
Once finished with the fabric, I like to add fake moss for finishing and to hide any flaws where the foam doesn't meet the fabric.
Step 5: Illuminate and Enjoy
I up-light these with a variety of par l.e.d. light fixtures. The inside caps are lit with programmable l.e.d. string lights.
When using in a public setting, be sure to use tie lines for stability, especially when using outdoors.
Making of video: