Venting A Lean To Roof . The lean to, at the rear of the house was a quick way to cover. It looks something like a ridge vent, but both deflectors. Venting A Lean To Roof Rickyhil Outdoor Ideas Lean To Roof from rickyhil.com You can only see the 2 from the back laneways. The lean to, at the rear of the house was a quick way to cover. When i talked with the builder today, he said that we don't need to install ventilation baffles.