Best waterproof garden shed floor? Thoughts on Pavelock?

[Minty]

I want to make my new garden shed floor as watertight as possible. My other garden shed was installed on concrete pavers 3cm thick, but water keeps seeping into the shed inside wetting things in there. It was professionally installed and I believe they bolted it down and then sealed it around the inside edges in places with a regular sealant, but it doesn't appear to have been enough to keep the water out which is very frustrating and literally a waste of my money. 

So I would like some advice on my second shed floor. I can't have a concrete slab so that really only leaves concrete pavers again. I am wondering if it would be okay to lay the concrete pavers then put a steel frame over them and then some sort of floor over the steel frame so that the shed is raised off the ground. What does anyone think of that method?

The person who is going to install the shed said it was overkill and all it needed was to lay the concrete pavers and then seal them with pavelock to make them watertight, and then once the shed is installed then put a sealant around the edges inside. I'm not sure about this method as I have no experience with pavelock, but as someone who is anti pesticide and anti chemical I am worried that it's very toxic and the poisons could leach out eventually which could be inhaled by anyone near the shed. 

Thank you for any advice. 

[Akanksha]

Hello @Minty,

Many thanks for your question on waterproofing your new shed floor. I'm sure our resident D.I.Y. expert @EricL will be happy to assist and provide his thoughts around Pavelock and other methods when he's back online later today.

If possible, are you able to provide any photos of where the shed is going to be installed or any other relevant photos? This may help our members get a better idea of what you're working with and allow them to provide more tailored advice. 

While waiting, I also encourage you to have a read of our step-by-step guide How to waterproof a shed floor in case it helps. You may also find the following discussions useful: 

• How to seal the bottom of the shed? by @MattR85 
  
  
• How to seal the bottom of shed walls? by @jjebw.

Akanksha 

[EricL]

Hello @Minty 

Thanks for sharing your question about having waterproof flooring for your shed. Since you are not keen on having a concrete slab on the soil, I suggest building a timber frame on DEKO 250 x 150 x 150mm Instant Concrete Foundation Block. These blocks are easy to use and can easily be moved if you need to change position. 

Since the shed flooring is above the soil it will prevent any rainwater or moisture from settling in the shed floor. As for the floor itself, I suggest using 2440 x 1220mm 12mm Plywood Hardwood Marine AA Grade If you are looking for further protection you can line the inside flooring area of your shed with BGC Fibre Cement 2450 x 1200 x 9mm Durascape Fibre Cement Sheet. 

I've sketched up a sample frame to give you an idea of what the flooring can look like. I also suggest having a quick look at these guides - How to build a Low-level deck by @Adam_W and How to Build A Deck by @MitchellMc.

If you have any other questions we can help with, please let us know.

Eric

[Minty]

Hi Akanksha, thanks so much for the links to the articles and step by step guide, appreciate it very much. 

[Minty]

Hi Eric, thanks so much for taking the time to explain this shed flooring option for me, and the diagram is really helpful. It's along the lines of what I was thinking but wasn't sure what materials exactly were needed. So I really appreciate the pictorial to assist me in that. Also the links to the articles as well which will be helpful to read. 

Just one question, will this flooring method be suitable for a 3m x 1.5m shed?

[Minty]

The weeded area is the proposed site for the 3m x 1.5m shed in my backyard. There is 900mm distance from the house wall.Hi Eric, just had another question if that's okay. 

The person who is installing my shed (who is a Bunnings shed installer) has said that I don't need to bother with all of that fuss with things like the Decko blocks, frame etc. He said that all I need for the shed floor are concrete pavers with pavelock which will 100% keep any water, weeds, etc, out. 

Is this correct?

Also, if I have to take the option of using concrete pavers for the shed floor, can I use them without pavelock and then just use a sealant such as Sikaflex 11FC which I saw recommended on another post here? Or would you recommend something else?

In the latter situation which would be the best type and size and thickness of concrete pavers for a 3m x 1.5m shed, to give it the best chance of being as watertight as possible?

Thank you. 

[EricL]

Hello @Minty 

Thanks for the additional information and the picture of the proposed site. Pavers being a porous material often hold moisture inside of them. When the temperature is cold enough it causes condensation on the surface of the paver. To add an extra layer of protection against moisture, I recommend putting in builder's plastic on the ground and then put the pavers on top of the plastic. The plastic will serve as a moisture barrier to prevent ground moisture from passing through the gaps of the pavers. 

The Sikaflex 11FC will provide an adequate seal between the pavers and keep them together. The adhesive is stronger than Pavelock and it will last much longer even with vigorous cleaning of the shed floor.  

It all depends on your budget and how much protection you want to give your items in the shed. I still believe that the elevated frame would give you better protection. One extra plus in having an elevated frame is that even if there is a large deluge of rain or a severe thunderstorm, your shed floor will be high and dry.

In regards to the type of paver, I propose getting something that is at least 40mm thick so that it can carry some weight. I also recommend getting the biggest one at the most affordable price so that that there are fewer gaps. A good example would be the Custom Concrete Products 600 x 600 x 40mm Plain Paver.

Let me call on our experienced members @Dave-1, @TedBear and @JoeAzza for their recommendations.

If you need further assistance, please let me know.

Eric

[Noyade]

Evening @Minty 

"3m x 1.5m shed"

Sounds like a pathway? Only 1.5 metres wide?

Do you have access to a concrete mixer?

I'm thinking you make a small concrete slab.

[Dave-1]

Good evening @Minty 

I would also be concerned about water into my shed. All the sheds I have seen built at ground level end up having water run through them.  Both bconcrete flooring and paving ones. I like @EricL's idea as being the most dry long term.

If money was an issue you could still have a raised floor using pavers or bricks to rest the timber on. I like the idea of a raised floor for air circulation and ease that water can run away. With pavers even with the plastic barrier underneath water can still come in from the top. What type of shed are you going to have? Is it a premade that is put together?

Looking at your picture one question is where will the water go when it rains, wether you use pavers or raised its always an idea to follow the path of last resistance with water.

Dave

[Minty]

Hi Noyade

Yes its definitely 1.52m depth x 3m wide. 

No, its not a pathway lol. 

No I don't have access to a concrete mixer but thank you for your suggestion though, many people have suggested a concrete slab to me as well! Unfortunately its not an option for me. 

Regards.