Such houses were usually designed for families with servants. These properties do not adapt easily for life with machinery.
Servants needed to be kept away from the nobs when they weren't serving, so the house would be divided into a warren of tiny rooms: kitchen, dining room, drawing room, parlour and so on, plus servants' quarters in the attic.
In the classic British town house, the arrangement is made even more awkward by the number of floors and endless stairs. The kitchen was almost invariably in the basement and the dining room on the ground floor, a unacceptable arrangement today when homeowners like to join in the conversation as they prepare the meal for their guests.
Even families that have servants often find period properties difficult - because servants today demand more than a bunk in the garret. Larger town properties inevitably have a self-contained flatlet, usually in the basement, for the maid or housekeeper.
Mike Neale of Form Design Architecture has adapted many period houses in London and is just starting on a project to bring a Georgian house in Kennington up to date as a buy-to-let.
He has modernised three of the lovely early Georgian houses in Meard Street, Soho. Such houses pose a challenge because they are listed Grade II*, which bans major structural changes.
The big alteration is to move the kitchen from the basement to the ground floor. "The original occupants would be shocked to find the new owner cooking in front of his guests in the formal panelled reception rooms," Neale says.
Installing a fitted kitchen would have damaged the panelling, and been difficult given the wavy 18th-century surfaces. So Neale designed free-standing units.
The period panelling was not deep enough for electrical sockets, so these were mounted in the floor.
The top floor was probably a workshop originally, with large windows so that the craftsmen could work for as long as possible without lighting expensive candles. This space was converted into a master bedroom suite to provide a "retreat" at the top of the house.
"You have to think laterally, but period terrace houses are surprisingly flexible and adaptable to modern living," Neale says.
Juliet Hill, lettings manager for Knight Frank in Kensington, says that a large family room is essential to let a house quickly these days. "Families now want a really good family area, and formal dining rooms are rarely needed," she says.
The usual solution is to knock through the basement to form a kitchen/family room open to the garden behind, although this often deters foreign tenants.
"Some tenants don't understand having family space underground," Hill says. But the alternative is to knock through the ground floor, which tends to result in having to put a bedroom in the basement."
Bathrooms can be a problem where the original layout is for bathrooms on the half-landings, which precludes ensuites. "You always need an ensuite in the master bedroom and if possible the guest bedroom," Hill advises. "If the two main bedrooms are sufficiently large, you can often insert shower rooms between them."
Hill is recently let a house in Kensington that shows what can be achieved with a dark basement. It has been extended into the garden, with large patio windows and a skylight. An island worktop means the cook can prepare the meal as guests talk.
The latest technology is coming to the aid of investors who want to install the latest gadgets for tenants but cannot drill holes in period panelling or plasterwork. Wireless systems can distribute TV and audio signals, as well as providing internet access everywhere. Traditional appliances such as boilers are also getting smaller, reducing their impact.
And the basement is also coming back into demand as a home cinema.
"At the top level, people love having a half cinema and half gym in the basement," Hill says.
"Tenants do not regard it as essential but they love it if it's there - it can certainly tip the balance in favour of the property."