They are not added to the basis of the land. They are depreciated over a 20 year life. From Pub 946: Although you cannot depreciate land, you can depreciate certain land preparation costs, such as landscaping
costs, incurred in preparing land for business use. These
costs must be so closely associated with other depreciable property that you can determine a life for them along
with the life of the associated property.
Here are some more
capital improvements:
- Remodels and room additions
(including decks and porches)
- New or upgraded landscaping,
irrigation, sprinkler system
- Hardscape such as pavement,
block or retaining wall, patio
- Fencing
- Swimming pool, spa
- Storm windows, doors
- New roof
- Central vacuum or security
system
- Upgraded wiring, plumbing,
duct work
- Central heating, AC,
humidifier
- New furnace, water
heater
- Filtration, soft-water, or
septic system
- Built-in appliances
- New flooring or wall-to-wall
carpeting
- Upgraded insulation
- Satellite dish
https://www.irs.gov/pub/irs-pdf/p946.pdf
