Mansard roof design

Mansard Roof Design: See a Mansard Roof on Your House

A mansard roof has two slopes on each side: a steep lower slope, usually with dormer windows, and an almost flat top. It gives a full extra floor of rooms inside the roof, which is why people search for mansard designs when they plan a loft or top-floor extension, or a French or Second Empire style house. This AI mansard roof design tool starts from a picture: upload a photo of your house, a sketch or a clay model, and ArchitecturesAI renders it in the same view; then describe the slopes, the slate and the dormers in a sentence. The result is an idea picture of the outside. It is not planning drawings, a structural design or a quote.

Upload your house photo or sketch

Sign in with Google or email to render. New accounts get 2 free renders (watermarked); free renders are not available in India on this site.

A plain two-storey cream rendered house with a flat roof and a low parapet, white windows in two rows, a front door, a small front garden and a pavement — An AI-generated pair made with our own image model. The "before" is an AI-drawn stand-in for a photo of a flat-roofed house, not a real house. Edit prompt used: "Add a mansard roof on top of this house as a new top floor: a steep lower slope in dark grey slate rising from the top of the walls with three evenly spaced dormer windows in white frames, a nearly flat upper roof above it, and a thin black metal edge where the two slopes meet. Keep the two floors below, the walls, the windows, the door, the garden, the pavement and the camera angle exactly the same." What followed it: a steep slope in dark grey slate with three evenly spaced dormers with white frames; the ground floor, the walls, the door, the garden and the pavement stayed. What differs from the prompt: instead of adding a new floor on top, it turned the front of the upper floor into the mansard slope, so the house is still two storeys, and the break between the two slopes is hard to see from the street. We ran this one once.

The same house where the front of the upper floor is now a steep dark grey slate mansard slope with three white framed dormer windows, above the same ground floor, garden and pavement — An AI-generated pair made with our own image model. The "before" is an AI-drawn stand-in for a photo of a flat-roofed house, not a real house. Edit prompt used: "Add a mansard roof on top of this house as a new top floor: a steep lower slope in dark grey slate rising from the top of the walls with three evenly spaced dormer windows in white frames, a nearly flat upper roof above it, and a thin black metal edge where the two slopes meet. Keep the two floors below, the walls, the windows, the door, the garden, the pavement and the camera angle exactly the same." What followed it: a steep slope in dark grey slate with three evenly spaced dormers with white frames; the ground floor, the walls, the door, the garden and the pavement stayed. What differs from the prompt: instead of adding a new floor on top, it turned the front of the upper floor into the mansard slope, so the house is still two storeys, and the break between the two slopes is hard to see from the street. We ran this one once.

What makes a mansard roof

Designing Buildings, This Old House, Houzz galleries and the Tower Hamlets council guidance on mansard extensions describe the roof the same way:

Two slopes on every side: a steep lower slope, close to vertical, and a shallow upper slope that is often hidden from the street.
Dormer windows in the steep slope, so the roof holds a full floor of rooms.
Slate is the classic finish, with lead or zinc on dormers and edges.
It is named after the French architect François Mansart and is the signature roof of Second Empire houses.
In cities such as London a mansard is a common way to add a top floor to a terrace; councils publish rules on set-backs and materials, so check before you build.

How to try a mansard roof design with ArchitecturesAI

In the editor above, the mode is Render Architecture, the type is Residential and the style is Classical. This mode has no prompt box: you start from an image.
Under Select Image, upload a JPG or PNG: a daylight photo of your house taken from the street, with the whole roof in view, or a sketch, a clay model or a screenshot from your 3D software.
Click Generate. Free accounts can only use Low quality (Medium and High are marked PRO). Sign in with Google or email when asked.
To steer the result, click Edit Image on it (the box is called Edit Instructions) or use Custom Action, and describe the mansard slopes, the slate or other roofing, the dormers and the trim and what must stay the same. Each edit is another render and uses credits. Run it a few times, since every result differs.
The three examples below ran directly on our image model with the written instructions shown. They did not go through the editor above, so your own results will differ.

Upload your house photo or sketch

A mansard on a flat-roofed house

Adding a mansard to a flat-roofed house is one of the most common uses. The slate and the dormers came through, but the model rebuilt the upper floor as the mansard instead of adding a floor, as the caption explains.

A Second Empire sketch and a terrace extension

A sketch of a full Second Empire house and a mansard on one house in a terrace both kept their setting. The caption notes where the terrace extension differs from a typical set-back design.

A black pencil line sketch of a symmetrical Second Empire style house with a tall mansard roof, arched dormer windows, tall windows on two floors and a central front porch with brackets — Both images are AI-generated with our own image model. The sketch is an AI-drawn stand-in for a hand sketch, not a real drawing. Edit prompt used: "Turn this line sketch into a realistic daylight photo of the same house: grey slate shingles on the mansard, white trim and dormers, pale blue painted siding, black shutters, a black front door, iron cresting on the roof top, a lawn and a brick path. Keep the house shape, the mansard roof, the dormers, the windows, the porch and the camera angle exactly the same." What followed it: grey slate on the mansard, white trim and dormers, pale blue siding, black shutters, a black front door, iron cresting along the roof top, a lawn and a brick path; the house shape, the mansard, the dormers, the windows and the porch stayed as drawn. What differs from the prompt: the brackets under the eaves are simpler than in the sketch. We ran this one once.

A photo-like render of the same house with a grey slate mansard, white dormers and trim, pale blue siding, black shutters, a black front door, iron cresting on the roof top, red brick chimneys, a lawn and a brick path — Both images are AI-generated with our own image model. The sketch is an AI-drawn stand-in for a hand sketch, not a real drawing. Edit prompt used: "Turn this line sketch into a realistic daylight photo of the same house: grey slate shingles on the mansard, white trim and dormers, pale blue painted siding, black shutters, a black front door, iron cresting on the roof top, a lawn and a brick path. Keep the house shape, the mansard roof, the dormers, the windows, the porch and the camera angle exactly the same." What followed it: grey slate on the mansard, white trim and dormers, pale blue siding, black shutters, a black front door, iron cresting along the roof top, a lawn and a brick path; the house shape, the mansard, the dormers, the windows and the porch stayed as drawn. What differs from the prompt: the brackets under the eaves are simpler than in the sketch. We ran this one once.

A row of plain two-storey yellow brick terraced houses with low slate roofs, white sash windows, black and blue front doors and small front gardens behind low brick walls — An AI-generated pair made with our own image model. The "before" is an AI-drawn stand-in for a photo of a row of terraced houses, not a real street. Edit prompt used: "Add a mansard roof extension to the middle house only: a new top floor with a steep lower slope in grey slate set back behind the front wall, two lead-clad dormer windows in it, and a flat top; the two neighbouring houses keep their low roofs. Keep the brick fronts, the windows, the doors, the front gardens, the neighbouring houses and the camera angle exactly the same." What followed it: a new top floor on the middle house only, with a steep grey slate slope and two dormers, and a flat top; the brick fronts, the windows, the doors, the front gardens and the neighbouring houses stayed. What differs from the prompt: the new floor rises almost flush with the front wall instead of being clearly set back behind it. We ran this one once.

The same row where only the middle house has a new top floor in a steep grey slate mansard with two dormer windows, while the neighbours keep their low roofs — An AI-generated pair made with our own image model. The "before" is an AI-drawn stand-in for a photo of a row of terraced houses, not a real street. Edit prompt used: "Add a mansard roof extension to the middle house only: a new top floor with a steep lower slope in grey slate set back behind the front wall, two lead-clad dormer windows in it, and a flat top; the two neighbouring houses keep their low roofs. Keep the brick fronts, the windows, the doors, the front gardens, the neighbouring houses and the camera angle exactly the same." What followed it: a new top floor on the middle house only, with a steep grey slate slope and two dormers, and a flat top; the brick fronts, the windows, the doors, the front gardens and the neighbouring houses stayed. What differs from the prompt: the new floor rises almost flush with the front wall instead of being clearly set back behind it. We ran this one once.

What the AI keeps and what it may change

Usually kept: the camera angle, the floors below, the neighbours and the street.
Often different from what you asked: whether the mansard is a new floor or replaces the top floor, how far it is set back, and small trim details.
Not visible from the street: the flat top of the roof.
Never produced: floor plans, structure, cost estimates or approval drawings.

Planning a loft or top floor?

The dormer page covers single dormer windows, the second storey addition page shows full new floors, and the Victorian and Georgian house pages cover other period styles.

Free tier and plans

You need a free account to render. New accounts get 2 free renders, and free renders carry a watermark. In India this site does not include free renders, so a paid plan is needed there. Weekly, monthly and yearly plans for more renders without the watermark are on the pricing page.

The houses and the sketch on this page are AI-drawn stand-ins, not real. Each example was run directly on the model, not through the tool above.

Frequently asked questions

What is a mansard roof?

A roof with two slopes on each side: a steep lower slope with dormer windows and a nearly flat top. It turns the roof space into a full floor of rooms.

Can I see a mansard extension on my terraced house?

Yes, as an idea picture. Upload a street photo, render it, then use Edit Image to ask for a mansard on your house only. Check your local council rules before building, since many set limits on mansard extensions.

Is there a text box in the editor?

The prompt box exists only in Architecture Generator mode. The editor above opens in Render Architecture, where you upload an image and change the result with Edit Image (Edit Instructions) or Custom Action.

Is it free to try?

Yes. After you sign in, a new account gets 2 free renders with a watermark, in Low quality. In India this site does not include free renders. Paid weekly, monthly and yearly plans are listed on the pricing page.

See a mansard roof on your house

Upload a photo of your house or your sketch, compare a few mansard versions, and take the best one to your architect. Your first 2 renders on a free account are on us.

Upload your house photo or sketch