Adding a roommate: Sublease, lease addendum, or a new lease?

Adding a roommate is really a question about liability, meaning who is legally responsible for the rent and the condition of the unit. You have three main paths, and they are not interchangeable. A sublease, a lease addendum, and a brand new lease each place responsibility in a different spot, which matters enormously if your new roommate stops paying or moves out early. Before you hand anyone a key, decide which structure fits your situation, and get your landlord's blessing first.

Get landlord consent before anything else

Almost every lease requires the landlord's written permission before another person can move in. Adding someone without asking usually violates the occupancy or subletting terms and can put you in default, which risks eviction for everyone. So the first step is never the paperwork. It is the conversation.

Ask your landlord in writing how they want to handle the addition. Many landlords have a preferred method, whether that is amending the existing lease, signing a fresh one, or approving a sublet. Getting their answer up front tells you which of the three routes below is even available to you, and it keeps you on the right side of your current agreement.

Option one: A sublease

A sublease is an agreement between you, the original tenant, and the new person, who becomes your subtenant. Your name stays on the master lease, and you remain fully responsible to the landlord. In effect, you become a middle layer. Your roommate pays you, and you continue to owe the landlord the full rent regardless of whether your subtenant pays.

This route can make sense when you are leaving temporarily, such as for a semester abroad or a work assignment, and want someone to cover the space while keeping your own lease intact. The trade-off is real exposure. If your subtenant stops paying or damages the unit, the landlord looks to you, not to them. Only sublet when your lease and your landlord permit it, and put the terms in writing so your subtenant's obligations to you are clear.

Option two: A lease addendum

A lease addendum, sometimes called a roommate agreement addendum, adds the new person directly to your existing lease as a co-tenant. Everyone signs, including the landlord, and the original lease stays in force with the new name folded in. This is often the cleanest option when a roommate is joining for the long haul rather than temporarily covering for you.

Once your roommate is a co-tenant on the lease, they answer directly to the landlord, not just to you. That usually means the landlord can pursue either of you for the rent, which brings us to a concept worth understanding before you sign. Alongside a formal addendum, many roommates also sign a separate room rental agreement between themselves to spell out who pays what share, how utilities are split, and house rules, none of which the landlord needs to police.

Joint and several liability

When two or more people are co-tenants on the same lease, they are almost always bound by joint and several liability. In plain terms, each tenant is responsible not just for their own share but for the entire rent. If your roommate fails to pay their half, the landlord can legally demand the full amount from you, and vice versa.

This cuts both ways and is the single most important thing to grasp before adding a roommate to your lease. It means a roommate who vanishes leaves you holding the whole bill, at least until you can work it out between yourselves. It also means a roommate's damage to the unit can become your problem at move-out, since the landlord can pull the full cost from a shared deposit or pursue any co-tenant for it. A separate written agreement between roommates does not change what the landlord can collect, but it does give you a clear record of what each person promised, which helps if you ever have to chase an unpaid share or an uneven deposit deduction in small claims court.

Option three: A brand new lease

The third route is to tear up the old lease and have everyone sign a fresh one together. This resets the arrangement so that all roommates are original co-tenants from day one, with equal standing and shared responsibility to the landlord. It is common when a household changes significantly, such as when one roommate leaves and a new one arrives, and the group wants a clean slate.

A new lease agreement also lets everyone renegotiate terms, including the rent, the length, and the deposit, rather than inheriting an older set of conditions. The downside is that it can restart your lease term and may require a fresh deposit and application for each person. If your landlord prefers this approach, treat it as a genuine reset and read the new document as carefully as you read your first one.

Which one should you choose?

Match the tool to the situation. Choose a sublease when your absence is temporary and you intend to return, accepting that you stay on the hook. Choose a lease addendum when a roommate is joining a stable household for the duration of the existing lease and everyone is comfortable with joint and several liability. Choose a new lease when the household is changing enough that a clean reset, with renegotiated terms and shared standing, serves everyone better.

Whichever path you take, put it in writing, get the landlord's signature where required, and make sure every adult understands who owes what. A roommate arrangement that feels friendly today can turn tense if money gets tight, and the clearest protection you have is a document that says plainly what each person agreed to. Talk through the awkward questions before anyone moves in. Decide how the deposit will be split and refunded, what happens if one person wants to leave early, and how you will handle a shared bill that goes unpaid. Settling those points on paper at the start is far easier than untangling them later.