Lucas A. Ferrara in New York Times Real Estate Section, INSTALLING A FOOD DISPOSAL UNIT, August 28, 2005.

Q I live in a rent-controlled apartment in Manhattan. Am I permitted to install a food disposal unit under my kitchen sink, at my expense, if my landlord refuses to do so? And if my landlord agrees to install one at his expense, how would any rent increase be calculated? ... C. Brody, Manhattan.

A Lucas A. Ferrara, a Manhattan real estate lawyer and editor of Landlord-Tenant Monthly, said that it would not be advisable for the letter writer to install a food disposal unit without the written consent of the landlord.

"Most leases prohibit alterations or modifications that are structural in nature," Mr. Ferrara said, noting that while it may not always be clear whether a particular alteration is structural or merely cosmetic, the safest course is to assume that changes to the building's systems are structural modifications that require approval.

And while a rent-controlled tenant may not have a lease, such a tenant could be subject to liability or possible eviction if alterations or modifications made by the tenant result in damage to the building or cause problems for other tenants.

"Since installation of a food disposal unit involves both plumbing and electrical work, and since the waste from the unit can clog pipes elsewhere in the building, the letter writer would be well-advised to get the owner's permission before installing such a unit," Mr. Ferrara said.

If the landlord agrees to allow the tenant to install the unit at the tenant's expense, Mr. Ferrara said, no rent increase would be allowed. As a practical matter, however, if the landlord is inclined to allow for the installation of the unit, he is likely to want to do the work himself.

That is because the landlord would then be entitled to a permanent monthly rent increase equal to one-fortieth of the cost of the installation - provided, however, that the tenant consents to the increase. If the tenant does not consent, Mr. Ferrara said, it is unlikely that the landlord will agree to the unit's installation.

Finally, he said, while a landlord does not need the approval of the State Division of Housing and Community Renewal to impose such an increase, rent-controlled tenants must sign a special form (RN-79b). The increase would be effective on the first rent payment date after the owner's filing of the document with the state agency.