Fill Cracks In Wood Deck

How to Fill Cracks in Wood Deck


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You might be an owner of a restaurant that has an open wooden deck or have paved the outside gazebo with a wooden deck. This process which we are going to learn can be applied there. Over the years of constant usage, the deck develops cracks. Since wood shrinks during winters and swells up during the rainy season, these cracks appear on the surface. When that happens, the wooden deck looks ugly and shabby. If you have been wondering, how to fill cracks in wood deck, continue to read further.

If the wooden boards are used for an external purpose, even the constant exposure to moisture and heat causes the wooden deck boards to crack. If the decks are used as flooring, the weight which is exerted on them when people walk on them or drag suitcases and bags creates hairline cracks.

A cracked wooden deck is a constant source of embarrassment to any homeowner and finding the right craftsman to do this job is quite cumbersome. Even if you find the right workman, he will charge a good amount of money.

Getting Started

So, if your wooden deck otherwise is sound and not rotten from the inside, you need not worry about how to fill cracks in wood deck. You can use a wood stain, wood filler, or a protective sealant and take care of the cracks or holes. It is a good idea to seal off the wooden deck once every two years. The costs for repairing the cracks and small holes are minimal, however, if you leave them unattended, you will need to change the complete wooden deck soon.

You can use two of your weekends to complete this project. The gap will ensure that the wood is completely dry before you apply the wood sealant. Also, if you are doing the project in an open area, the sky needs to be clear and there should be no rains. It is better if the day is sunny as it will aid the process of drying the wooden deck.

Any paint-based sealant coating should not be subjected to splashed water or humidity before 48 hours. It needs at least that much time to dry completely.

Ingredients Needed – How to Fill Cracks in Wood Deck

There are two ways we need to approach this project. If there are cracks and holes in the wooden deck, which are less than four inches in length, we need to have one approach for repairing them. And if the cracks are deeper than four inches, there is a separate process to follow.

You will need a plastic garden sprayer, deck wash solution, brightener, plastic sheets, hose pipe, water, scrub brush, protective gear (work gloves, gumboots, googles, face cover), to complete this project. To finish the sealing work, you will need wood stain, water repellent, paintable acrylic caulk, putty knife, nail puller, and a new wooden plank.

Step-by-Step Instruction- How to Fill Cracks in Wood Deck

To Fill Cracks in Deck Under Four Inches in Length

Now you are getting to the point of starting the process of how to fill cracks in wood deck.

Step 1- Inspect the Entire Deck

Commence the project by inspecting the entire deck. You need to pay special attention to any area that is in direct contact with sunlight or water. Even to any area which touches the ground like the posts or joists. A joist is a length of timber that is arranged in parallel series to provide support to a floor or ceiling. Take a screwdriver and sink its tip in every crack to check the depth. To avoid further damage to the wooden deck, you need to get to work immediately.

While inspecting the deck, if you find any part which has completely rotten, remove it immediately. Cut the wood to the centerline of the nearest joist. You need to attach a similar-looking wooden cut piece. Now is the turn to check the handrails and balusters. Replace any damaged handrails and balusters.

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Step 2- Cover the Surroundings to Protect Them

Before you start the process of filling the cracks on the deck, it is a good idea to tape plastic sheeting over the siding or structures next to the deck. Put a protective covering till about waist height to ensure that any spillage from the wooden sealants, cleaners, etc. will not damage them. If there are items underneath the deck, if possible, remove them too. Else cover them with plastic sheets.

If you are going to use plant-friendly solutions and cleaners, then misting the plants before you start the work will be a good idea. The chemicals won’t spoil or burn the leaves and stems of the surrounding plants. If you are planning to use acids, strong corrosive agents, strong cleaners, then it is advisable to cover the plants with plastic sheeting beforehand.

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Step 3- Spray the Cleanser

Pick up a plastic garden sprayer and fill it with deck wash solutions and a brightener. Spray the entire deck with the mixture which will be the base of your cleaning process.

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Step 4- Scrub the Deck Clean

For the decks that were not stained using a wood stain earlier, use a good quality deck cleaner and scrub it. You can even make your own solution by adding one-quart household bleach (sodium hypochlorite), 1/3 cup of laundry detergent powder, and three-quarters of warm water. After mixing them thoroughly in a bucket using a good quality scrub to clean the entire length and breadth of the deck. Ensure that the scrub does not leave any scratch marks on the wood. Make sure that all the dirt, grime, stains are removed during the process.

If the deck was stained with wood stain previously, then you cannot use bleach on it. You need to wear your protective gear (gloves, gumboots, face covering) and fill up the sprayer using the stripper solution. Let the stripper sit on the deck for about 15 minutes to ensure the cleaning process is done properly. Put a caution board while you are working to avoid any accidents due to slipping on the solution. Even you need to be careful while performing this step.

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Step 5- Spray Water from Garden Hose

Keep your protective gear on even while using water from a hosepipe to clean the wood deck. Now spray the entire deck, wooden staircase, handrails, balustrades with the spray from your garden hose.

This step will remove the cleanser solution from the wooden board and the gaps. If you think that the force of the water from the hose pipe may damage any part of the wooden deck, use a scrub brush instead. Wash the board with water until the foamy water turns into clear water.

The work for the first weekend is complete here. Allow the wooden deck to completely dry up before you perform the next steps.

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Step 6- Sand Everything Smooth

Allow the wooden deck to dry up. Use a moisture meter if you are not sure. Moisture content of 15% or less is needed for the wood to be ready for staining. If you live in a moderately humid, sunny area, it takes about four consecutive days without rain for the deck to dry up completely.

Wear a dust mask and use a sanding pole and 50-grit sandpaper to sand the entire deck. Do not forget to include the handrail, staircases, and balusters. Then use a vacuum cleaner to remove all the dust, fine particles, and sawdust. After you have finished vacuuming the surfaces of the wood, use a tack cloth to clean the wood further. This step will remove the fine dust particles which were hidden in the pores of the wooden plank.

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Step 7- Test the Surface on Decks that Were Stained Earlier

For the wood, which was stained earlier, after sanding it, you need to check for any residual wood stain. Pour a few capfuls of water into different areas of the wooden deck and check if the wood absorbs the water quickly. If the water beads up, you need to sand that area again.

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Step 8- Stain the deck, Railings, Balusters

Once you have cleaned the wooden deck properly, removed the old wood stain, it is time to apply the protective sealant to cover the cracks. If your wood is new (in this case it will not be) you can use transparent stains. But for old wood, it is better to use colored stain so that the old scratches or discoloration does not show up.

The colored pigment will give a smooth sheen to the wooden deck and safeguard the wood from the harsh rays of the Sun. The wood stain will be absorbed into the wood and provide a thin covering. If you would have used wood paint, then there would have been chances of it peeling off after a few months of use. Do not forget to apply wood stain to railings, posts, top rail, bottom rail, balusters, and any other part of the deck which is visible.

It is a good idea to apply two coats of wood stain on the main wooden deck as people will be walking over it. Use a clear water repellent on the wood stain to increase the life of the coating. Normally a synthetic filament brush is used for applying water repellent.

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Step 9- Fill the Cracks

Using a putty knife, plug any cracks on the wooden board, railings, balusters, posts that are less than four inches in length. Use a latex wood filler that will not swell, shrink, crack or flake when exposed to harsh weather conditions. Ensure that the wood filler is meant for outdoor application.

You can also use paintable acrylic caulk to fill any holes and cracks deeper than 1/4 inches. Ensure that the wood is completely dry before performing this step. Use a putty knife to scrape off the excess material before it sets in.

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Step 10- Drying

Now you learned how to fill cracks in wood deck. You will have to allow the deck to dry for at least four days before you start using it. You can even think of painting the deck after this.

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To Fill Cracks in Deck Over Four Inches in Length

Step 1 – Remove the Nails

Use a nail puller to pull out the nails of the wooden plank in which there are visible cracks. If the cracks are deeper than 4 inches, then you will need to replace the wooden plank.

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Step 2- Replace the Board

From the deck joists, you have to pull out the entire length of the wood as it is rotten beyond repair. Get a new piece of wood of the same size and use 2-inch wood screws to secure them at all of the joists. You can even flip the old piece of wood if the other side is good and usable and attach it the same way.

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Step 3- Clean the Deck

Now follow all the steps for cleaning, sanding, and sealing the complete deck just the way you had done earlier (step 3 to 10). Cover the deck with a plastic sheet in case there is a forecast of light rain.

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Now you learned the complete process of how to fill cracks in wood deck. Put it to real practice and enjoy your free time doing something productive. In turn, you will pick up a new skill and save a lot of money too. So why not use that money for some investments? During the current pandemic, when many people across the globe lost their primary sources of income, you must have realized the value of every penny. Happy DIY Project!!!