Mod: Insulated Floor – Part Six
During this part of the project, I install the plywood sub-floor and seal it to protect it against moisture. As you may notice, I forgot about the staining until after the installation and fastening of the plywood, so only the visible plywood was sealed with Shellac. You may also stain the other side or abstain entirely as sealing is clearly an option.
Project Insulated Floor Content
What You’ll Learn:
- How to cut the plywood sheets by using the paper templates.
- How to add dadoes to lock-in the plywood.
- How to fit the plywood sheets.
- Why to seal the plywood.
What You’ll Use:
- Table saw.
- Small paint brush.
- Wide paint brush.
- Tape measure.
- Painter’s tape.
- Safety glasses.
- Hearing protection.
- Hand saw.
- Circular saw.
What You’ll Need:
- Paper templates (made earlier in this project).
- 3 sheets of bcx plywood (exterior grade) – 4′ x 8′ 15/32” each.
- 4 oz of Shellac flakes.
- 32 oz (4 cups) Denatured alcohol.
- Marine varnish or
Approximate Duration For This Project: 4½ hrs. for the plywood and an additional 2 hrs. for the Shellac.
The basic composition of the sub-floor in an RV or van conversion should consist of a bottom layer of one-half to one inch of Poly-Iso insulation and a top layer made of exterior grade plywood. The standard ¾ inch thick plywood is sufficient to securely hold all cabinetry and appliances. Don’t use MDF or Particle board as these products have weight and/or moisture issues.
For practical reasons, I have to deviate from these standards as a result of the roof height. The medium roof Ford Transit has an interior height of about 69 inches between the top of the floor ribs and the ceiling cross members. Even with my personal average height, there is very little space left for floor or ceiling materials, without sacrificing the ability to stand up straight in the vehicle.
If you have a high roof vehicle all of this does not apply, but I decided to only use Poly-Iso insulation strips in between the floor ribs, with only a half inch thick plywood sheet on top of that. That and taking my shoes off, will hopefully solve this issue.
Weight is another issue that may change your choice of materials. These sheathing materials are heavy and make a big impact on the overall weight allowances of the individual vehicle. Dependent on the tonnage and size of the van, you may decide to use relatively lighter or thinner materials. The half inch (actually 15/32 inch) thick plywood that I use, adds another 73.5 lbs to the conversion.
As a sub-floor, I prefer to install the plywood sideways as the finish flooring will be installed lengthwise on top of that. But the size of the floor will probably dictate, how to lay the plywood most efficiently to save a few bucks in materials. I ended up using three sheets of plywood, with lots of scraps leftover.
Gather all the tools and materials before proceeding. Regularly fit the materials, to avoid costly mistakes.
- Tape the paper template to the plywood.
- Mark the cut-out areas.
- Cut out the marked areas. Stay within the lines, to slowly ease into the final cut.
- Check regularly by fitting the ply sheet.
- Mark and cut any additional areas that need to be removed.
- While fitting, make sure that a ¼ inch gap exists between plywood and the surrounding areas. Adjust as necessary.
- Cut the rear plywood sheets width at the center of the central floor rib plus ¼ inch.
- Cut dadoes at the front & back (from the top, ½ inch wide, ¼ inch deep) and left side (from the bottom, ½ inch wide, ¼ inch deep) of the right, rear plywood sheet.
- Cut dadoes at the front & back and right side (from the top, ½ inch wide, ¼ inch deep) of the left, rear plywood sheet.
- Cut a dado at the back (from the bottom, ½ inch wide, ¼ inch deep) of the front plywood sheet.
- Be sure, the dadoes interlock.
Sealing the plywood floor has the advantage of protecting it against rot and mold. It also makes these materials more difficult to ‘breathe’, where moisture can evaporate and the materials can dry,
So, optionally you can apply some protection to it with a (Marine) varnish or polyurethane. I love to use Shellac. As a hobbyist woodworker, I use Shellac flakes, mostly because I can store it for an extended period, while the canned version has to be used within a few months.
For this application, I use a 1 pound cut (4 oz of flakes with 32 oz/4 cups of Denatured alcohol) and it takes a day for it to be ready to use. Just add the two together and swirl regularly to help to dissolve the flakes. It has an orange/amber tone when dry and it dries quickly; add Denatured alcohol if you need more time.
Clean up is easy: give brush a swirl in Denatured alcohol and let dry. It will dry stiff, but gets back in shape the next time you use Shellac.
Shellac Flakes: The Shellac Shack
Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand and used as a brush-on colorant, food glaze and wood finish.
- Prepare the Shellac solution the day before.
- If you paint in the right sequence, clean the plywood and apply the Shellac on both sides and edges, if not:
- Vacuum the floor.
- Paint the edges.
- Paint the surface.
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This part of the project involves heavier materials and heavier tools, yet is still within the grasp of the ordinary DIY’er. The use of the tablesaw can easily be substituted by a circular saw or a router.
The plywood was acquired locally and the Shellac flakes on-line and the total cost was about $76.00.
Other projects of this Van Conversion:
- Mod 1: 12V OUTLET TO DUAL USB
- Mod 2: BACKUP PARKING SENSOR
- Mod 3: CABIN CURTAIN
- Mod 4: INSULATED FLOOR
- Mod 5: FLOOR VENT
- Mod 6: MURPHY BED/DESK
- Mod 7: CCP FUSES
- Mod 8: FRONT PARKING SENSOR
- Mod 9: CAR RADIO REPLACEMENT
- Mod 10: 4 CAMERA MOBILE DVR
- Mod 11: ROOF VENT
- Mod 12: 15 AMP HOOKUP CABLE
- Mod 13: SHOWER-IN-A-BOX
I’m just a DIY’er with a lot of common sense, but with some of the projects, I use some tools and materials, that require you to really know, what you’re doing. Always read the manual and consult an expert if you’re in doubt.