How to Build Your Own Boat Hardtop

Updated February 21, 2017

As the boating season warms up and spring becomes high summer, you may find that bit of shade from your convertible bimini top over your cockpit is just too small and, as cooler nights take hold in late summer, you may want more roof than a bimini offers. Even if you don't have a bimini on your boat, build a hardtop as a solution to the desire for shade, protection from weather and even privacy.

Use a measuring tape to measure the area you wish to cover with the hardtop. Transfer these measurements to a sheet of marine plywood.

Cut the marine plywood to size using a circular saw. Paint one side and all the edges of the marine plywood with marine epoxy. Lay the fibreglass cloth onto the marine epoxy and work the fibreglass cloth into the epoxy on the flat surface with the putty knife. Cut 1/4-inch-by-1/4-inch square notches out of the corners of the fibreglass cloth to allow it to fold down onto the sides of the plywood.

Apply a coat of epoxy to the fibreglass and lay another layer of fibreglass cloth on the first, notching the corners of the fibreglass cloth as before. Work the fibreglass cloth into the freshly applied epoxy with the putty knife. Use scissors to trim any excess fibreglass cloth. Allow the epoxy/fibreglass to cure completely.

Sand the fibreglass with your palm sander and 120-grit sandpaper to smooth out any high spots. Paint with marine paint or apply gel coat to the fibreglass and paint the bottom of the plywood with a light-coloured marine paint. Allow the paint or gel coat to cure thoroughly.

Attach the hardtop to the bimini top frame by setting eye straps (a "U"-shaped fastener with screw holes on the ends of the "U") over the frame's tubing and securing them to the bottom (the non-fibreglass side) of the hardtop with wood screws. Attach the frame to your boat with a bimini mount appropriate to the frame.


New bimini tops can cost £195 or more, but used or scrapped frames in excellent condition can be found at most boatyards or even some auto scrapyards for much less. Add snaps to mount clear curtains around the edge of your hardtop for protection from weather.


This project involves working with power tools, chemicals and fibreglass. Appropriate caution is urged.

Things You'll Need

  • 1/4 inch marine plywood
  • Pencil
  • Measuring tape
  • Circular saw
  • Marine epoxy
  • Fibreglass cloth
  • Putty knife
  • 120-grit sandpaper
  • Gel coat
  • Marine paint
  • Frame for a bimini top
  • Eye straps
  • Screwdriver
  • Wood screws
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About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.