How to seal the shed?

[adnanqureshi]

Hello,

I recently acquired a new shed, but it had gaps from the floor area to the roof. To address this, I filled the floor gaps with cement to keep water, dust, insects, and air out of the shed. However, during the last few rainy days, water has been seeping in from all sides of the shed, with no apparent source in the middle or any other specific area. Could you please advise me on what steps I should take now? I am really surprised how this water came in.

Thank you

[adnanqureshi]

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.

[adnanqureshi]

I have noticed someone shed like in the pictures. Mine looks similar. Wondering what they did from inside and outside to kind of seal it.

[JacobZ]

Hi @adnanqureshi,

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

[adnanqureshi]

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

[JacobZ]

Hi @adnanqureshi,

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

[adnanqureshi]

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 put any concrete there because it sits on the concrete slab itself.

Thank you

[JacobZ]

Hi @adnanqureshi,

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

[adnanqureshi]

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

[JacobZ]

Hi @adnanqureshi,

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