How to waterproof a shed floor

[MitchellMc]

Difficulty: Beginner

Water seeping under shed walls can cause damage to your stored items and be a potential safety hazard.

Here is a simple guide to waterproofing a shed on a concrete slab using an aluminium angle and sealant. 

You can also keep items dry in your shed by installing a new floor. Check out our guide How to install a shed floor for step-by-step instructions.

Let us know if you have any questions.

Steps

Step 1

Clean the concrete slab.

Use a pressure washer to remove any dirt or debris on the concrete slab outside the shed. Make sure the area is dry before proceeding. This will help ensure the aluminium angle adheres properly to the shed wall.

      

Step 2

Cut the aluminium angle.

Use a tape measure to measure the length of the shed wall that needs to be covered by the aluminium angle.

Cut the aluminium angle to size with a hacksaw. It's a good idea to use safety glasses and gloves while cutting. You can use a mitre box to cut the aluminium angle at a 45-degree angle for the shed corners. 

    

Step 3

Apply sealer under the shed wall.

Cut the sealer nozzle with a retractable knife and insert it into your caulking gun. Don't forget to wear safety gloves and cut away from your body.

Starting at one end, apply sealer along the bottom of the shed wall where it meets the concrete slab. Apply the sealer evenly and smoothly.

It’s important to apply enough sealer to contact the concrete slab and the underside of the shed wall. This will prevent the water from seeping under the wall and into the shed.

        

Step 4

Apply sealer on the shed and concrete slab.

Apply two more sealer beads, one on the vertical face of the shed's bottom trim and one directly in front of it on the concrete slab. This will help ensure the aluminium angle is firmly secured to the shed wall and concrete slab.

      

Step 5

Attach the aluminium angle.

Attach the aluminium angle to cover the gap between the shed wall and concrete slab. Press the angle firmly against the wall and concrete, ensuring it is level and straight.

Repeat Steps 1 to 5 for all four walls of your shed. If a smaller trim piece has been used on the bottom of your shed's door, apply only the sealant to the door's front edge.

You have now successfully sealed your shed.

        

Materials

• Aluminium angle, like Metal Mate 20 x 12 x 1.4mm 3m Aluminium Unequal Angle - Silver
• Sealant, like Sika 300ml Grey Sikaflex 11FC Plus Polyurethane Adhesive Sealant.

Tools

• Tape measure
• Mitre box
• Caulking gun 
• Retractable knife 
• Hacksaw
• Pressure washer 
• Safety glasses 
• Gloves. 

Images

                                            

[KatieC]

Thanks Mitch!

Those looking for more great how-to guides on repairs around the home, head to our How To section and select the topic Repairing. These include guides like How to repair a water damaged ceiling and How to fix a muddy lawn.

If you have more questions about repairs, please don't hesitate to reach out. We are always happy to help. 

Katie

[mich1972]

This is great for everyone who has a shed. Is it yours @MitchellMc ? 

[MitchellMc]

The steps show my shed @mich1972. Plenty of items I've stored in there were damaged from water entering under the walls. Now I'll be able to keep items out of the weather and safe from moisture damage.

Mitchell

[Iain]

Although it might be considered overkill in this situation, the following extra step at the start would be an improvement: Use pressure cleaner to blast as much rust off the bottom strip as possible. Paint rusty strip with rust converter followed by appropriate paint.

[MitchellMc]

That would certainly be an option @Iain, and would assist with preventing further degradation of the steel trim. However, I would hope that additional step shouldn't be needed in most cases as my shed is in fairly poor condition. This area and trim were covered with soil for many years. I'm not willing to accept fault for that one as I'm renting. 😄

Thanks for your input, as I trust any of our members with a similar-looking trim will appreciate your advice.

Mitchell