How to waterproof and verminproof the base of shed wall

[RRhys]

So I have an old shed that was put together poorly.  I want to convert it into a studio for my darling spouse. First step is waterproofing and verminproofing the walls (then insulate, internal walls etc). 

As you see from the photos, there is flashing just sitting under the wall. 

So I'm thinking that I need to rivet the flashing to the wall, sikaflex under the flashing and maybe then expanding foam between flashing and wall on the inside? 

Any tips on the project generally - walls, membranes, plastering much appreciated!

 Here are a couple of pics of the current situation.

  

[MitchellMc]

Welcome to the Bunnings Workshop community @RRhys. It's great to have you join us, and many thanks for your question about waterproofing a shed.

You’re on the right track with your initial ideas. Start by securing the flashing to the base of the shed walls using corrosion-resistant rivets or screws, ensuring the flashing extends slightly over the ground or slab to direct water away. Apply a generous bead of Sikaflex or a similar sealant underneath the flashing to create a watertight seal. 

On the interior side, use expanding foam to fill any gaps between the flashing and the wall to prevent vermin from entering. If you have a significant vermin issue, you might like to incorporate wire mesh, which they can not chew through. For additional protection, consider installing sarking over the interior walls before adding insulation and internal cladding. When it comes to plastering, use moisture-resistant plasterboard or panels to withstand any residual dampness.

Please let me know if you have any questions.

Mitchell
 

[RRhys]

Thank you @MitchellMc . 

That's great that I can fix the flashing direct to the tin wall. I was worried I might need to install another layer to fix it to. Will I need to silicon the rivets? 

With the sarking, how do I attach that to the tin wall? And do I need a gap between the tin wall or sarking and insulation bats?

Thanks in advance!

[MitchellMc]

Hi @RRhys,

You likely won’t need to seal the rivets, but adding a touch of silicone over their heads can provide extra protection and ensure a watertight finish.

As for the sarking, it should be attached to the timber frame of your shed, positioned between the frame and the tin wall. This placement allows the sarking to act as a moisture barrier while supporting the insulation’s performance.

While an air gap between the tin wall and the insulation isn’t strictly necessary, it can help reduce heat transfer and improve energy efficiency by providing additional thermal separation. If feasible, including a small gap is beneficial, but the insulation will still perform effectively without it.

Mitchell