A lean-to roof is a roof structure with one pitch, where the building’s one wall is higher than the other, resulting in a sloping roof. This makes a lean-to roof acceptable according to South African National Building Regulations which state that, instead of simply being durable and waterproof, roofs must be durable and not allow the penetration of rainwater or any other surface water to its interior. A lot of early 1900s Cape Dutch structures can be seen flaunting lean-to roofs providing shade for patios.
It is the simplest type of pitched roof (also known as a sloping roof) and is generally the cheapest alternative for covering a structure.
Lean-to roofs can be used for a multitude of different structures, both in South Africa and abroad, ranging from family homes and covered porches/patios to garden sheds and carports. Lean-to designs made of glass are also popular for conservatories and/or green houses.
First determine whether that lean-to roof will be for an unheated outbuilding or a habitable room. If it’s habitable, the roof will need to be insulated and treated to a moisture barrier to keep the warm, moist air away from the cold roof. Should it be an unheated outbuilding, simple ventilation is enough so that the outside is about the same temperature as the inside.
Lean-to roofs present an interesting problem as they increase with size: if the roof pitch is very steep, it will rise to a height that can be quite unsightly. This unpleasantness can mostly be avoided by installing a low-slope roof to keep the rise of the roof at a minimum.
Material ideas for covering a lean-to roof include:
· Metal, which is available in multiple options and well-known for its affordability.
· Asphalt shingles, which is also an agreeable and affordable alternative. Asphalt shingle roofing works well on narrow and small leans.
· Simple and straightforward designs.
· Easy construction.
· Low costs.
· Ideal for allowing rainwater to slide down.
· Limited structure design.
· Similar to gable roofs, wind can be a hazard.
· Can mean quite low ceilings for certain rooms.
It is important to first consult with local building authorities to determine the relevant building codes and permits that might affect your lean-to roof construction. In addition, be sure to locate any possible underground hazards. Most lean-to structures will require some digging for a concrete foundation, for example, and the last thing you want is to damage a water pipe or electric line while breaking soil.
If you’re not an accomplished DIYer, it’s recommended to let a seasoned professional assist you.
Be sure to work off a proper design that specifies the structure’s length, height, etc. Also take weather into account, as the roof needs to be angled so that rain is directed away from the building’s perimeter. A gutter or drainage piping might also be required to prevent pooling.
For a straightforward approach to building a simple lean-to roof, see the following steps:
· Mark the floor area where you want your lean-to structure.
· Measure about 2.5m from the existing structure (i.e. your house) towards the outer direction, where you will dig a hole deep enough to drive a post in.
· After driving the hole in, fill up with concrete to set it in place.
· From this post, measure approximately 900cm in the same line, dig another hole and drive a second post in. Do the same for the third and fourth posts, maintaining the same distance in-between.
· Cut out a notch on top of the posts where the supporting post will rest.
· After placing the supporting posts into the notches, attach the metal purlins on the outer edges of the installed posts – secure these firmly in place with nails.
· Fasten the nailer on the side of your existing structure. Make use of good-quality screws to drill in the nailer. The upper part of your rafters will be attached onto this.
· Attach two planks on either ends of the nailer by nailing them firmly in place, and place them on top of the structure. Add a third plan to the centre.
· Set the roofing material by attaching wooden planks at regular intervals on top of the roof as done previously.
· Place your roofing material (measured accordingly) over the base roof structure and screw it in with a drill and nails.
· The final step involves you installing the trim of your choice as a cover against the side structure, which should be screwed in with a drill and nails.
Keep in mind that your lean-to roof structure needs to complement your house’s façade.
From swimming pools and kitchens to gardens and roofs, homify provides an ever-increasing collection of inspiration for those interested in the building- and interior design world. In addition, we also help to put you in contact with a wide variety of professionals (both in South Africa and abroad) such as architects, interior designers, landscape architects and roofers, to ensure you have a range of experts to choose from for your project at home.