ᐅ Lean-to Roof Design – Ridge Area

Hello everyone,

I am building a chicken coop (with an insulated roof) and have a question regarding the construction/details of the shed roof.

The planned build-up (from inside to outside) is as follows:
- OSB board (interior ceiling)
- Insulation
- Sheathing
- Underlay membrane
- Counter battens
- Supporting battens
- Trapezoidal metal sheet H12 + verge profile

I have never built a roof like this before and would appreciate any tips on, for example, how to design the ridge so that no snow, rain, or pests can get in. Originally, I planned to simply lay roofing felt on the sheathing and then put the trapezoidal metal sheet directly on top, but I guess that might cause problems after a few years, right? What are your ideas? Keep in mind it is "just" a chicken coop, so the effort should be balanced accordingly.

Looking forward to your feedback and tips!

Many thanks.

Your structure is basically fine, but the top edge needs a bit more attention to detail. For the shed roof, replace the ridge with a neat edge using a verge or wall connection profile plus sealing tape; otherwise, rain or snow will inevitably get underneath. It’s also important to ensure there is air circulation between the underlay membrane and the trapezoidal metal sheet—so definitely don’t skip the counter battens.

Placing roofing felt directly under the metal sheet is not a good idea, as condensation will build up and you’ll quickly get mold on the OSB. If you want a simple and durable solution, a sandwich panel with a polyurethane core might be a smarter choice.