Use sealant
Applying sealant between the tin shed and the wall can fill the gap and prevent water leakage. Therefore, adding a layer of sealant between the tin shed and the wall can prevent water and insects from entering.
Use extended packaging
Expansive filler is a kind of material that fills the gap. These fillers are usually used to fill gaps between walls and windows. You can add it to all the gaps between the tin shed and the wall. This filler has flexibility and usability, and can maintain long-term integrity.
Fill the joints with cement
Another way to solve the gap between the tin shed and the wall is to fill the gap with cement. You can fill the gap with cement by hand until the whole gap is filled. If the gap is small, it can be filled with mortar.