The Ultimate Guide To Replacing Your Boat's Floor

Boat floors need to be replaced when they show signs of rot and decay, which can be identified by a soft, spongy feel. Replacing a boat floor is not a simple task and requires professional skills to work with tools such as a circular saw, drill, and chemicals. The process can take up to 400 hours or more, depending on the size of the boat. The first step is to remove all components attached to the old floor, including consoles, chairs, and wirings. Then, the old flooring needs to be dismantled, and new flooring needs to be measured and cut. The new floor is then installed, and the removed items are reinstalled. The type of flooring used is also important, with marine plywood and pressure-treated plywood being common choices.

How to Replace Boat Floor

Check for rot and decay

Checking for rot and decay is a crucial step in boat maintenance and repair. Here are some detailed instructions to help you through the process:

Inspect the Boat's Exterior and Interior

Thoroughly examine the flooring, transom, fixtures, deck, and any other surfaces for signs of decay. Look for any sagging or giving way of the flooring, which could indicate rot underneath. Pay attention to any discolouration, as this may suggest underlying issues.

Check the Transom

The transom is particularly susceptible to rot. Inspect it from both the inside and outside of the boat for any signs of bowing, deformation, or cracks. Use a flashlight to look for signs of rot or discolouration on the inside of the transom where there is no gel coat. Push down on the motor; if the transom gives way, it could be an indication of rot.

Conduct a Tap Test

Use a small hammer or coin to gently tap the surface of the boat. A solid, crisp sound indicates that the surface is likely in good condition. However, if you hear a dull thud or a hollow sound, it could be a sign of rot or delamination. Conduct this test on the transom and floor, especially in areas that are susceptible to water intrusion.

Look for Other Signs of Rot

• Soft or spongy areas on the deck or hull
• Visible cracks, blisters, or discolouration
• Warping or distortion of the boat's surfaces
• Musty odours or visible mould growth
• Dirty water seeping out from behind bolts or screws, especially around the transom

Use Your Nose

Rot often has a distinctive smell. If you detect an odour reminiscent of funky sunbathed mushrooms, sweaty football gear, or mothballs, it could be a sign of rot.

Drill Test (For Suspected Soft Spots)

After identifying potential soft spots through the tap test, use a hand drill to drill a small hole through the fiberglass. If the drill pushes the wood down easily, it confirms the presence of rot.

Remember, if you identify rot, it is essential to address the issue promptly. Depending on the extent of the damage, you may need to repair or replace the affected sections. It is crucial to maintain the structural integrity of your boat to ensure the safety of you and your passengers.

Remove items from the floor

Removing items from the boat floor is the first step in replacing a boat floor. This is inevitable, as anything attached to the previous deck will need to be removed. This includes consoles, chairs, and wirings. It is important to disconnect any wiring or connections before removing them from the boat.

When removing items from the boat floor, it is recommended to keep as much of the old flooring intact as possible. This is because it can be used as a template to measure the new flooring pieces and as a guide to line up screw holes during reassembly. Leaving a trim of the old flooring around the edge of the boat is also important to ensure that the sides of the boat remain undamaged during the removal process.

In addition to removing items from the boat floor, it is also necessary to check the transom for any signs of decay. This is because, in most cases, when the floor requires replacement, there are rot problems in this area as well.

Dismantle the old flooring

Dismantling the old boat flooring is a crucial step in the replacement process. Here are some detailed instructions to guide you through this stage:

Remove Attached Components:

Start by removing all items attached to the old floor, including consoles, chairs, seats, and wiring. This step ensures that you have unobstructed access to the flooring and prevents any accidental damage to these components.

Prepare for Cutting:

Before you begin cutting, determine the ideal depth for your circular saw to avoid damaging the hull. A depth of ⅝ inch is commonly used in most projects. Put on protective gear, including goggles, a face shield, hearing protection, and a mask, to ensure your safety during the cutting process.

Cut with Care:

Use your circular saw to trim around the edges of the boat, leaving at least three inches of the old flooring intact. This trim will serve as a support frame for the new flooring and prevent puncturing the sides of the boat. Go slowly and carefully to avoid any accidental damage to the boat's structure.

Preserve the Template:

Try to keep the old flooring as intact as possible. You can use it as a template for cutting the new plywood and lining up screw holes during reassembly. This will save you from complex dimension measurements later on.

Remove Old Flooring:

After cutting, carefully remove the old flooring from the boat. Be cautious not to damage the sides of the boat during this process. You may need an extra pair of hands to lift and manoeuvre the old flooring, especially if it's heavy or awkwardly shaped.

Measure and cut the new flooring

Before you start measuring and cutting the new plywood, ensure that you have removed all the damaged or decayed parts of the old flooring. You can use portions of the original floor as a guide to measure how much plywood you need to cut. A tape measure will help you double-check before cutting.

When cutting the plywood, you should follow the old flooring dimensions for a perfect fit. If your boat floor is wider than the standard 4x8-foot sheet of plywood, you can either buy an oversized sheet of marine plywood or splice two narrower sheets together. For example, if your boat floor is 52 inches by 8 feet, you could buy a 4x10 sheet of plywood and cut it in half to make two 4x5 pieces. Then, rotate and join these pieces to create a 5x8 foot sheet.

To join the plywood sections, use an aluminium strap and secure it with large flange rivets. Place the strap on the underside of the floor, making sure it doesn't touch any of the keel or cross-member supports. Pre-drill the strap with rivet holes, then drill through the plywood. Apply marine silicone to the holes and around the strap before riveting and wipe away any excess.

Once you have cut and joined the plywood, "dry fit" the new floor in your boat to check the fit. Leave at least a 1/8-inch gap on each side, and trim or sand the edges if necessary.

Soak the Plywood in Epoxy

Before installing the new floor, soak the plywood pieces in marine epoxy to seal out water. This step will help to waterproof the plywood and extend its lifespan. Epoxy can take a few hours to dry completely, so factor this into your project timeline.

Mark Screw Holes

After the epoxy has dried, mark the screw holes on the plywood. You can use the old flooring as a guide to line up the screw holes for reassembling the deck. Drilling new screw holes before laying the flooring down will make the installation process smoother.

Install the new floor

Before installing the new floor, check the other parts of the boat. Only lay the new floor down when all decay is removed.

First, you will need to measure and cut the plywood, using the old flooring dimensions as a guide. Then, soak the wood pieces in marine epoxy and leave them to air-dry. This step will help further waterproof the plywood. Once the epoxy is dry, mark the screw holes and drill.

Apply epoxy on the areas of the new plywood that will be included to provide water protection. Once it has dried, use a drill to mark out the appropriate areas of the plywood that you need to screw in place. It’s better to have holes as a guide when laying down the cut plywood.

Now, you can lay down the cut plywood. Before installing, check the other parts of the boat. Only lay the new floor down when all decay is removed.

Cover the flooring with a mat

Now, most of the hard work is done. Go ahead and cover the plywood flooring with the fiberglass or vinyl mat. Seal it in place using epoxy resin. Wait until the resin is totally dry. Then, drill holes and use screws to help secure the mat. Again, follow the screw positions of the previous flooring. Don’t forget to sand down the rough surfaces for a smooth finish.

Frequently asked questions