About this plan

A 20 by 24 foot cottage ADU under a lean-to roof, 480 square feet with one bedroom, one bathroom and a vaulted sleeping loft above. You receive these 20x24 adu plans as a PDF plan set.

Small enough to be allowed

480 square feet sits below the cap that many jurisdictions place on accessory dwellings, which is often the number that decides whether an ADU is approved at all. Building to that size deliberately, rather than trying to argue an oversized one through, is usually the faster route to a permit.

The loft and the ladder

Loft access is by ladder rather than stair. That is a real trade and worth understanding before you buy. A ladder costs you nothing in floor area, where a stair would eat perhaps forty square feet out of 480, which at this size is the difference between a living room and a corridor. It is less convenient at night and not suitable for everyone.

The loft itself is vaulted, and ceilings run from eight feet up to thirteen under the lean-to slope.

Outside and foundation

A front deck extends the living space. There is a laundry area inside. Slab, pier and crawl space foundations are all drawn, so the plan suits most sites without modification.

What you get

A complete construction set, supplied as a PDF:

• Dimensioned floor plans for each level, drawn to scale
• Exterior elevations on all four sides
• Building sections and construction details
• Foundation plan with floor, wall and roof framing layouts
• Electrical layout
• Window and door schedules
• Roof plan with pitch and overhang dimensions

Before you build

Accessory dwelling rules vary more than almost any other part of the residential code. Some jurisdictions permit them outright, some cap the floor area, some require a separate utility connection or an extra parking space. Check what your county allows before you order materials. The rules have been loosening across much of the country, so if you were told no a few years ago it is worth asking again.

Code requirements are set locally. The International Code Council publishes the model codes most United States jurisdictions adopt.

Other plans to compare

If these 20x24 adu plans are not quite the right size, browse every design in Cottage, or compare this one with Spruce Cabin, 34×36 and Farmhouse Cottage with Wraparound Porch. You may also want to look at Small Cottage, 30×30. You may also want to look at Small Loft Cabin, 12x20.

Common questions

Can I modify these 20x24 adu plans?

Often, yes. Common requests include moving a wall, mirroring the layout or adapting the foundation to your site, but what is possible depends on the plan, so ask for a free quote before you buy. Editable CAD files are not available for every plan; email us to confirm availability for this one.

How do I get the files?

Plans are supplied digitally as PDF files. Our Shipping and Delivery Policy explains how and when files are made available.

Can my builder have a copy?

Yes. Print as many sets as your contractor, your trades and your building department require.