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How to seal this garage shed from dust, water and insects?

Team, here are a few photos of a newly installed Garage Shed. I need some advice on how best i can seal the following.

#1. Gaps where Roof and Walls meet. [Photo 1 & 2]

#2. Gaps where Floor and Walls meet. [Photo 3]

You can see in one of the photos that some water has already come in from Yesterday's Rain.

I am planning to use expanding foam for #2 above. Would that be a good idea. Should i choose a Gap filler rod+ Sealant instead?

The Gaps described in #1 above are pretty big and i am worried that expanding foam may not be a good option.

Any expert advice would be highly appreciated.

Thanks

Faisal

Outside view of the roof.jpg Inside view of the roof.jpg Inside view of the Floor.jpg

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JacobZ

Hi @nfaisal,

Welcome to the Bunnings Workshop community, it is great to have you with us.

I wouldn't advise using expanding foam as it is not designed to get wet.

For the gap between the roof and wall, I would suggest you use Suntuf Black Greca Foam Infill and Sika 300ml Grey Sikaflex 11FC Plus Polyurethane Adhesive Sealant. You may need to remove the screws from the roof sheet to get the foam into place before rescrewing. The foam would only act as a backing for the Sika 11FC which will have to coat it entirely if you are looking to create a waterproof seal.

I would then seal the wall sheets using the same Sika 11FC. Run a bead along the outside where the wall sheets meet the concrete to prevent any water getting in underneath the sheets.

Please note that Sika 11FC is extremely sticky so you should keep a bucket of water and some clean rags nearby while carrying out this project. I would also advise using old clothes that you can bear to lose.

If you have any further questions, please don't hesitate to ask.

Jacob

nfaisal

Thank you, Jacob! Plz excuse me for asking another question. For the recommendation below.

"The foam would only act as a backing for the Sika 11FC which will have to coat it entirely if you are looking to create a waterproof seal. ",

Do i need to coat the foam from both sides?

EricL

Hello @nfaisal

It would provide you with a more solid seal if both sides were covered with the Sika 11FC.

If you need further assistance, please let me know.

Eric

Taf

Hi Jacob,

I have two problem areas

1. The gable end which is open and has no gutter outside.

2. The sides of the shed, which has a gutter already fixed in place )outside that debris collects in and then blows into the shed ( no matter

With regard to your comment 'The foam would only act as a backing for the Sika 11FC which will have to coat it entirely if you are looking to create a waterproof seal' , how would you suggest covering both sides of the foam for a shed that is already pre built.

1. Would it be a case of applying a lot of Sika, and then using a small spatula etc. to smooth the Sika over the entirety of the foam?

2. How would i get access to the external areas given that the gutters are already in place

Any other tips you can give would be greatly appreciated as well

MitchellMc

Welcome to the Bunnings Workshop community @Taf. It's terrific to have you join us, and many thanks for your question about filling gaps.

What Jacob was most likely referring to with the Sika 11FC is its use in areas where water is actually pooling on the floor and trying to push its way into the shed. In your situation with the gable end and the roof edges, I don’t think he was suggesting that the Sika be used along those roofing sheets.

For your project, the foam strips themselves are designed to block debris and prevent water from being blown back up under the sheets. I would start by carefully pushing the foam into the gaps along the gable and sides where the gutters are already installed. That alone should stop the majority of dust, leaves, and wind-driven water from entering.

If, after installing the foam, you still notice leaks or water ingress, you could consider applying SikaFlex on top of the foam to seal it. This would involve spreading it across the foam and smoothing it with a spatula, but it can be quite tricky in pre-built sheds, especially with gutters in place making access difficult. For most sheds, properly fitted foam strips are sufficient, and if not, it indicates that there is missing flashing on the exterior of the shed in those areas.

Please let me know if you have any questions.

Mitchell

AlanM52

Hi @nfaisal,

I would not use anything to fill any of the gaps because the shed needs to breath.

Use capping on the roof and the floor needs special attention.

The bottom edge of a colorbond (so similar) sheet is not protected so it's important to keep that clear of everything - leaves, debris & soil.

Can't remember where I got this when helping other people.

So ask the workshop lads for assistance.

Screenshot 2026-01-20 142621.jpg

Same for this, someone gave me 1/2 roll which I used up.

Cheers

Taf

Thank you Mitchell,

Your advice is much appreciated

I've just submitted a follow up post as well which leads on from my original question to the next stage of my project https://www.workshop.bunnings.com.au/t5/Garage-and-Shed/How-to-attach-insulation-and-plyboard-to-a-shed-walls-and/m-p/338749 .

cheers

Taf

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