DEV Community: Claudia Landy

Treat the room like an API contract: what a redesign must not change

Claudia Landy — Sun, 25 Oct 2026 15:45:52 +0000

Developers know the difference between an implementation detail and a contract. You can refactor the inside of a function all day, but if you change its signature, everything that calls it breaks. After years of working with homeowners as an interior designer and in real estate, I think rooms work the same way, and most redesign disappointments come from ignoring the contract.

The contract: walls, windows, layout

In a typical home, the walls, the windows, the doors and the overall layout are the interface. Everything else in the house depends on them: the plumbing runs, the light, the way people walk from the kitchen to the sofa. Changing them is a structural project with permits, contractors and a much bigger budget. Most people asking for a "new look" do not want that. They want a different room inside the same shell.

The implementation: everything you can swap

Paint, flooring, furniture, rugs, lighting, textiles and styling are implementation details. They can be swapped freely without breaking anything. This is where nearly all of the visible change comes from, and where homeowners can move quickly.

Why inspiration images break the contract

The classic mistake is falling in love with a photo of a different room. It has a bigger window, a higher ceiling, a wall in a place where yours has a door. You copy the sofa and the paint, and the result does not look like the photo, because the photo depended on an interface your room does not have. It is the design equivalent of copying code that calls a function with arguments yours does not accept.

Design against your own interface

The fix is to start from a photo of your own room and keep its fixed parts fixed. An AI interior design tool does exactly this: upload a room photo and it restyles the room in seconds, in looks such as Modern, Scandinavian or Japandi, while keeping your walls, windows and layout. The first image is free, no card. Because the structure stays the same, what you see is something you can actually build with paint, furniture and decor.

A small review checklist

Before approving a redesign, I run something like a code review:

Did any wall, window or door move? If so, it is a different project.
Does the furniture fit the real circulation paths in the room?
Does the light in the image match the light the window actually gives?
Can every visible change be bought or painted, without a contractor?

If the answers are no, yes, yes, yes, the design respects the contract and is ready to implement.

Thinking this way also makes conversations with partners easier. You agree on the interface first, then argue about the implementation, which is a much cheaper argument to have.

Version control for a floor plan: how I iterate on room layouts

Claudia Landy — Sun, 25 Oct 2026 15:13:25 +0000

When I work with clients who write software for a living, I notice they treat a floor plan as a finished drawing, something you get right once. In practice a good layout is iterated, the same way you would iterate on a design document. These are the habits I borrow from development when I plan a room or a whole floor.

Start from a measured baseline

Every iteration needs a reliable starting point. Measure each wall at waist height, note where doors swing, and mark windows, radiators, outlets and vents. Ceiling height matters too if you are thinking about shelving or a loft bed. This baseline is your main branch: you do not change it, you branch from it.

One change per version

If you move the sofa, the bed and the desk at once, you cannot tell which change made the room work. I save a copy, change one thing, and walk through the result in my head: where do you enter, where do you put down your keys, can two people pass each other?

Write down the constraints like tests

Some rules every version must pass:

About 90 cm of clear walkway on main routes through the room.
Doors and drawers can open fully.
No furniture blocking a radiator or the only outlet on a wall.
In bedrooms, space to walk on at least one side of the bed.

A layout that looks good but fails one of these will annoy you every day.

Review it with someone else

A partner or flatmate will spot the problem you stopped seeing, usually the route to the bathroom at night or where the laundry basket goes. Treat it like a code review: walk them through the plan and ask what is awkward.

Keep the history

Keep old versions. Clients often come back to version two after trying version five. Dated file names are enough.

The tool I use

For quick drafts I sketch rooms in a floor plan maker before I touch any furniture. Having the plan on screen makes it easy to save versions, compare them side by side and share them with a contractor or designer. The first image is free, no card needed.

Ship it, then measure again

Once the furniture is in, live with it for a week and note what you bump into. That feedback is the next version. A floor plan is never really finished; it just stops changing because it works.

Modelling a home renovation budget like a developer would

Claudia Landy — Sun, 25 Oct 2026 14:33:20 +0000

I spend my working days around houses: listing them, staging them and helping owners plan renovations. A surprising number of my clients are software people, and they all ask the same thing: "how do I estimate this properly?" The honest answer is that a renovation budget is a small data model, and the habits you already use for code make it much better. Here is the structure I give them.

Break the project into line items, not rooms

"Kitchen: $40k" is not an estimate; it is a guess with a label. Split each room into items you can price independently: demolition, electrical, plumbing, cabinets, worktops, flooring, painting, fixtures, labour. Each line has a quantity, a unit and a unit cost. If you cannot fill in all three, you have found the part of the project you do not understand yet.

Separate materials from labour

Materials prices are easy to look up. Labour depends on your region and the trade, and it is often half the cost or more. Keeping the two in separate columns makes it obvious where quotes differ, and lets you swap a finish level without touching the labour line.

Use ranges, not single numbers

Give each line a low, expected and high value. Summing only the expected column hides risk. Summing the high column on the risky lines, such as anything behind a wall or under a floor in an old house, gives you a far more honest total.

Add contingency as its own line

Ten to fifteen percent for a straightforward job, twenty percent or more for older houses. Make it explicit rather than padding each item, so you can see when you are spending it.

Version your estimate

Every quote you receive is effectively a pull request against your model. Keep the old version, note what changed and why. When the final bill arrives, you will know exactly which decisions moved the number.

Sanity-check against a second source

Before collecting quotes, I compare my line items with an independent estimate. A remodel cost calculator that prices by room, size, finish level and ZIP code is useful here: each item is broken into materials plus local labour, with a timeline and a published source for every number, so you can see where your own figures look optimistic. It is free to try.

Track actuals as you go

Add an "actual" column and fill it in as invoices arrive. The difference between estimate and actual on your first project is the best calibration data you will ever get for the next one.

A spreadsheet with a few columns is enough to start. What matters is treating the budget as a model you test and update, not a single number you hope comes true.

What AI room redesign tools can and can't do (notes for people building or evaluating them)

Claudia Landy — Sun, 25 Oct 2026 04:29:03 +0000

If you are building a tool that takes a photo of a room and returns a redesigned version, or you are just evaluating one, this is a summary of where the category tends to work and where it tends to break.

The core trick: change surfaces, keep structure

A plain image generator invents a new room. A useful room redesign tool has to do the opposite: keep the walls, windows, doors and perspective from the photo and change only what the user asked about. Most of the techniques here are variations of conditioning a diffusion model on structure, for example edges or depth estimated from the input photo. ControlNet-style conditioning is the best-known example. The effect for the user is that the window stays in the same place while the wall colour or the sofa changes.

Where it works well

Changing a surface: wall colour, floor material, cabinet fronts, curtains. The geometry is simple and the model has seen millions of examples.
Adding soft furnishings: rugs, pillows, plants, lamps. Small objects tolerate small errors.
Style transfer: taking the same room to Scandinavian, Japandi or industrial. Style is mostly colour, material and object selection, which diffusion models are good at.

Where it breaks

Straight lines and repeated patterns. Tile grids, wood planks and window mullions can drift. If you look closely at the edge of a tiled floor, you will sometimes see the grid wobble.
Text and small details. Labels, switch plates, outlet covers and books on a shelf are often garbled.
Reflective surfaces. Mirrors, glass tabletops and polished floors need consistent reflections, and models often forget what was in the room.
Scale. The output looks like a room, but a 90 cm sofa and a 120 cm sofa can look identical. If you want to measure anything, use a tape measure or a floor plan, not the render.
Hidden structure. Nothing in the image says where the pipes, the load-bearing wall or the outlet are. A good render of a kitchen island does not mean you can put one there.

Design implications if you build one

Show the original and the result side by side with a slider. Users trust a change they can compare.
Let people lock things. Floors, windows and ceiling should be protected unless the user explicitly picks them.
Be honest in the UI that the output is an inspiration image. People will otherwise take it as a quote or a plan.
Keep generation time under a minute. After that, people leave.
Handle bad input. Dark photos, ultra-wide lenses and photos with a person standing in front of the main wall all produce worse results, and a gentle warning helps.

A concrete example to try

If you want a quick feel for how this category behaves, try one. We build HausDraft's AI room design tool, where your first image is free, no card needed. Whichever tool you evaluate, give it your worst, darkest room photo first, because that tells you far more than a staged example does.

What the category still needs

Better support for floor plans and measurements next to the render, so that "I like this look" and "this fits in my room" are answered by the same tool. If you have built something in this area, I would be glad to hear what broke for you in the comments.

HausDraft

Claudia Landy — Wed, 23 Sep 2026 05:35:39 +0000

HausDraft

Draft your dream home in seconds — AI home design from a single photo.

HausDraft is the AI home-design studio for the whole home — interior rooms, floor plans & blueprints, exteriors, backyard & landscaping, and remodels — turning a photo or blank canvas into a redesign in seconds. Built for homeowners, renters, DIY renovators, home buyers, real-estate stagers, landscapers, and remodel planners.

Key features

Paint Color Visualizer — see paint colors on your own photo
Exterior House Color Visualizer — paint your house online
AI Home Exterior Design — reimagine your whole facade
AI Interior Design — redesign any room from a photo

Use cases

Renters visualizing changes without construction
Home buyers previewing a property's potential
Real-estate stagers preparing listings

Read the full guide: HausDraft.

More guides and tools at HausDraft.