This is a relatively easy build, makes a big impression, and should be versatile enough for lots of Halloween displays.
Rough list of materials:
- 1/2" plywood - 2' x 2'
- 1/2" foam board - about half a sheet (4'x 4')
- 1x2" lumber - about 2' worth
- 8' steel studs - 3
- Vinyl trim (like flashing) - about 6' x 3.5" wide
- 8" diameter HVAC flex duct - 25'
- 6" diameter flex duct - 25'
- foam pipe insulation - various diameters, 3 pieces
- screws, latex caulk, liquid nails, and paint
- fog machine and spot lights for extra wow
Step 1: The base
Note: If you are fitting something over a real sewer, realize you run, a likely very small, risk of having your utility company take exception to it and having to move it.
I started the base by cutting a 2' circle from the 1/2" plywood (a jigsaw is a good tool for the job).
Next I cut a 1x2 board into eight 2" lengths. Then I screwed these around the edge of plywood (see photo). These pieces act as standoffs for the plywood to sit flat since the real manhole cover (which will be left in place underneath) is slightly domed. Then everything was painted flat black.