How to seal the shed?

I am also confused how the water is coming inside knowing the fact the concrete foundation is high and the walls of shed are built around the concrete foundation.Sorry i am not very technical but in a nutshell the level of concrete is high.

I have noticed someone shed like in the pictures. Mine looks similar. Wondering WhatsApp Image 2024-06-03 at 10.00.50 PM.jpeg what they did from inside and outside to kind of seal it.

Thank you for your question and welcome to the Bunnings Workshop community, it is great to have you with us.

Is it possible to get some photos of your shed from the outside? Does the corrugated iron run past the edge of the slab or does it sit in a channel that is on top of the slab?

What you are seeing is a phenomenon called rising damp. This happens because concrete is a porous material, and the surface tension of the water is enough for it to cling to the concrete and rise through it.

This is prevented by using a damp-proof membrane. Did you have the concrete slab installed by professional concreters? They've likely used something like CAgroup 2 x 50m 200um Medium Impact Polypro Builders Film underneath the slab to create a barrier stopping direct contact between the concrete and the earth.

I'm sorry to say that if I'm interpreting your photos correctly, the concrete you've used to fill in the corrugations is likely the cause of this water entry. It is acting as a wick because I believe it is in contact with the ground outside the shed.

To stop this water ingress, I would suggest removing this concrete and replacing it with a combination of Suntuf Black Corrugated Foam Infills and Sika 11FC ensuring there is no direct contact between them and the earth outside.

Let me know if this helps and if you need further clarification.

Jacob

Hi Jacob,

The corrugated run past the edge of the slab i guess.The level of slab is above and the corrugated wall is low.I have filled the gap with Quick Set Cement thinking it will block the air etc.The concrete was done by professional.Kindly refer to photos.

Thank you WhatsApp Image 2024-06-04 at 10.32.29 AM.jpeg

I'm sorry to say it is as I suspected. The concrete you've added to block the gaps is actually acting as a wick drawing the ground water up into the shed.

The solution, like I said earlier, is to chip out the concrete you've added and replace it with foam infills and Sika 11FC that don't touch the ground.

Anything in direct contact with the earth will draw in moisture, so avoid having anything on the outside in contact with the foam infills.

Let me know if you need any further assistance.

Jacob

Hello Jacob,

Thank you for your prompt response. Kindly advise what tool i can use to chip this concrete. Also, one side of this shed is actually sitting on the concrete slab itself as shown in the picture. Should i use the same foam infills and sika 11FC there too. I haven't WhatsApp Image 2024-06-04 at 10.50.49 AM.jpeg put any concrete there because it sits on the concrete slab itself.

Thank you

No worries at all.

I'd suggest using a cold chisel and a hammer to chip the concrete away. This shouldn't be too difficult, but it can be a bit taxing on the knees so you might also like to consider grabbing a pair of knee pads.

Also, as you will be using blunt force, concrete chips will likely become airborne. Don't take any risks with your eyes, please make sure to wear eye protection.

Anywhere there is an air gap that you would like to fill, you can certainly use the same foam infills and Sika 11FC to seal them up. Just make sure they aren't touching the earth, only the shed and the existing slab.

Let me know if you have any further questions.

Jacob

Thank you so much Jacob.

One last question,when i am chipping from inside definately will need to remove/chip outside as well yeah? Just to make sure its like nothing and then wash the area/dry and then use the foam and the sealant.

Hopefully this will fix the issue.

Thank you

It's best to remove everything that wasn't the original slab. As concrete doesn't bond well to other concrete, it should be fairly easy to break it off and remove it all.

Let me know how you go, I'm here to help if you run into any issues.

Jacob

Thank you so much.

Appreciate your help. I will give a go and will let you know if i need further assistance.

Kind Regards,

Adnan

Hello,

WhatsApp Image 2024-07-12 at 10.55.08 AM.jpeg

Hello,

I desperately need help with this shed.I have now connected its downpipes to the stormwater tank which has improved the water on a couple of sides of the shed but still the water is coming in.To seal the gaps of corrugated walls on the floor,we have put cement and i think it has gone deep and thats why may be the water is coming in.Can someone please advise what should we do.Please note one side of the shed is exactly on the concrete slab and the rest is below/under it.

Thank you

Thanks for the follow up question.

I have moved it to your post from earlier so all the information is in one place.

Have you followed any of the advice I offered earlier?

My suggestions would remain the same.

Let me know if there's any issues or if you have any questions about this advice as it will still be the best way to address the water ingress issues with your shed.

Jacob

Hello Jacob,

Should i remove the cement which we have put to fill the the gaps on the floor.I am hesitating to do so because i think i might either damage the shed itself or the concrete foundation which costed a lot.

Should i try to remove the cement from outside shed which is in direct contact may be to the ground and taking the water in?

In addition, please guide how should i seal this side which is exactly on the concrete.Sorry i messed up all the information which you had offered earlier.Kindly explain again so it can make some sense to me.Appreciated.

Thank you WhatsApp Image 2024-07-12 at 10.55.08 AM (1).jpeg

Yes, you should remove the concrete that you've added to block the gaps. There will be two distinct concrete masses that are not interconnected so it should be easy to remove. I'd suggest doing it from the outside as there is less potential for you to hit the slab or the shed while carrying out the demolition work.

Once the concrete is removed, follow the same steps that I advised earlier to fill the gap where the corrugated sheets run past the edge of the concrete.

For the side where the sheets sit in a channel on top of the concrete slab, simply run a bead of the same Sika 11FC along the bottom edge of the corrugated sheets and the channel that the corrugated sheets sit in.

Seal the underside of the channel will stop water getting underneath, which I suspect is the issue. Running a solid bead of Sika 11FC the full length of the shed will stop the water getting beneath the channel.

You might like to have a look at How To Silicone a Gap for some advice on this.

Make sure you keep a bucket of water, and some rags nearby to assist with cleanup and smoothing the bead as it can be a bit messy if it's your first try.

Let me know if you have any other questions.

Jacob

Noyade

Hi @adnanqureshi

I'm sure @JacobZ has a better grasp of what's going on than me - but to my eyes, especially the external grassed areas - the slab looks too low?

Either that or my father deliberately made me stay on the cement mixer too long when we raised my shed slab in 1990. You can see the 1947 level.

K Mart boot for scale...

Thank you, Jacob, for this clarification. I have one more question sorry so i can look into it the way you are explaining, when i am sealing the underside of the channel should i do it from inside or outside.

In addition,when i using the foam and Sika 11FC to put in the channel and seal i have noticed the foam is big and channel is small to insert the foam in.You can notice in the picture as well there is a foam already but i havent put Sika 11FC though.

Kindly refer to photos below. Thank youThis is foam insert and should i then put Sika 11FC here or use Sika first in the channel and put foam on itThis is outside the shed under the channelShould i put Sika 11FC here which is inside the shed under the channel.

There's no need for the foam inserts on this side of the shed where the channel has been used. They are only needed where the corrugated sheets run past the edge of the concrete. They are only intended to act as a backing material to keep the Sika 11FC in place.

You should seal the bottom edge of the channel from the outside where you've highlighted in your second image. If you seal it from the inside, the water will be able to get underneath the channel but will be blocked from getting into the shed. This will allow the water to sit underneath the channel which can cause problems over time.

Let me know if you need any further clarification.

Jacob

Hello Jacob,

Thank you very much for all this explanation.Just one more question please,should i fill the gap where the corrugated wall is sitting on the channel itself as shown in the picture.When i will use Sika 11FC under the channel the gap between the corrugated wall and channel will be still there isnt.To fill it should i put Sika 11FC as well.

In addition,i do remember that you have mentioned to use foam and Sika 11FC to fill the same gaps on the all four sides of the roof.Is there any recommended way like how to use foam and Sika 11FC.Should i first put Sika and then use the form on it so it can stick together? Or should i use something different on the roof/ceiling.

Thank youRoof/Ceiling gapsGap between channel and corrugated wall from insideGap between channel and corrugated wall from outside

You can seal any of the gaps that you choose to.

I mentioned underneath the channel as it is the likely point of water entry, so this is the most important gap to seal, but if you wanted to take the time and expense to seal everything it would certainly be worthwhile.

The Sika 11FC can also be used to fill the gaps between the roof batten and the roof sheet. I'd suggest running a bead of the Sika 11FC along the top contoured edge and the flat bottom of the foam filler. Once you've applied the two beads, push it into place in the gap.

Keep in mind that this stuff is extremely sticky, so make sure you have a bucket of water and plenty of rags nearby to clean up if it gets somewhere you don't want it.

Let me know if there's any further questions.

Jacob