Years of updates, including elevator, skylight and roof-deck installation, kitchen and bath renovation, and smart-home technology assimilation, have made this 2,450-square-foot penthouse residence feel lighter, airier and roomier - more like a full house than the old mansard roof could do.

The mansard roof, popularized by 17th-century French architect François Mansart as a way to sneak tax-sheltered living space into a building by expanding it above its roofline, transformed the cramped, musty attic into full level living. Steeply sloped sides filled out the livable space. Full-height dormers brought in more light, sky and ventilation. The hipped top allowed maximum headroom.

Revived in Baron Haussmann’s reconstruction of Paris under Napoléon III from the 1850s onward, the mansard was concurrently adapted into the Back Bay’s French Second Empire rowhouse architecture for its space-creating, property value-boosting and elegant building-crowning capacities. Architect/contractor Charles Kirby capitalized on these qualities when he erected 136-138 Beacon St. in 1859-60.

Their roof-room was further expanded in 1936 by removing their dormers and building out their shared mansard into full penthouse apartments for both addresses. Modern Continental Enterprises’ 1980-82 unification of the buildings as one condominium combined these apartments into 136 Beacon St.’s double-width Unit 10.

Years of updates, including elevator, skylight and roof-deck installation, kitchen and bath renovation, and smart-home technology assimilation, have made this 2,450-square-foot penthouse residence feel lighter, airier and roomier - more like a full house than the old mansard roof could do.

The keyed elevator also transcends its typical limits, directly accessing the unit on two sides: to the hall to the living room and primary bedroom, or straight to the kitchen. The smart-home technology reaches beyond its own barriers to control the lighting in any room or area from wall-mounted consoles throughout the unit.

The sunny sky-lit living room flows into the dining room and kitchen through two archways in the white-painted brick firewall separating 136 from 138, showing how the penthouses were combined. The archways flank a wood-burning fireplace, letting its heat penetrate into the adjacent spaces. The segmental arches of these passages are picked up on the facing bookcases and grasscloth art wall. Casement and picture windows bring in sunny and starry views of the Esplanade, Charles River and Cambridge, which are especially spectacular during the annual Boston Pops concert on the Fourth of July.

“When they shoot off the fireworks here, you’ve got a front-row seat,” said John Forger, owner of Olde Forge Realty, which is offering the unit through his son Glenn. “And the Hatch Shell is right there in the trees, so you’ve got the music.”

The dining room offers the same skylights and two picture-window views, adding new dimensions to dinner parties. The open kitchen expands those dimensions with a skylight of its own and a running granite counter extending into a curved breakfast bar by the dining area and a peninsular counter across the hall from the elevator for unloading groceries upon entry.

The kitchen contrasts classic white paneled cabinetry with contemporary Jenn-Air stainless-steel appliances, including a double wall oven with microwave and a refrigerator with side freezer. The Jenn-Air smooth-top five-burner cooktop has induction cooking, in which a magnetic current heats food and boils water faster than standard coil burners.

For al fresco dining or cocktails amid a fuller park/river/sky view, the adjacent hall accesses stairs to the deck, which spans the entire double roof. An evergreen screen introduces one of two spacious terraces, which invite a large dinner party to enjoy one of the most breathtaking northwestern views of fireworks, sunsets, stars and sailing on the Charles River. Planters are handy for beautifying your experience. By the door to the deck is a deep closet for off-season grill/furniture storage or installing a wet bar for instant drinks.

Further down that hall are the carpeted second and third bedrooms. The second bedroom reprises the segmental arch theme on the bookcases flanking the bed area. Three windows with southeastern views of the Back Bay’s mansard roofs, church steeples and the Hancock towers are unified with a swag window treatment hanging from a valance that incorporates the crown molding, as the bookcases do.

A short hall of closets connects the bedroom to its en suite bath, also accessible from the main hall for the third-bedroom occupant’s convenience. Also convenient for that is the Carrara marble twin-sink vanity - rare for a second bedroom suite. Fabric lampshade sconces, glass subway tiles in the tub/shower combo with fixed and hand-held showers, and a chevron-patterned marble tile floor add more presidential-suite propriety.

The smaller third bedroom, suitable as a nursery, has two windows, a closet consolidating linen shelves and a coatrack, and a painted brick wall.

The hall from the living room passes a laundry/utility closet with a LG washer and dryer and HTP boiler and a storage closet with carpeted stepped shelving en route to the carpeted primary bedroom, where four southeastern windows offer ample morning light. The wood-burning fireplace boasts an antique arched Carrara marble mantel with a keystone carved as a heraldic shield.

At the end of a hall of closets, the marble theme continues in the en suite bath in creative mosaic forms. A variegated subway-tile marble floor distinguishes the deluxe walk-in glass shower with rain, fixed and hand-held shower heads. The wall segment holding the latter two shower heads is tiled in vertical strips to visualize a rain shower or waterfall. This effect is reprised all over the wall behind the Aria oval soaking tub with a “waterfall” faucet. The marble/wood twin-sink vanity is served by two all-mirror medicine cabinets interspersed with semi-cylindrical designer lights. The marble floor is radiant-heated.

Offered at $4,495,000, Unit 10 at 136 Beacon St. will put you “up on the roof” at the highest level. For a private showing, contact Glenn Forger of Olde Forge Realty at 617-293-2395 or glenn@oldeforgerealty.com.

Sources:

- “136 Beacon,” BackBayHouses.org, https://backbayhouses.org/136-beacon

- “Mansard roof,” Wikipedia, last edited Oct. 27, 2020, https://en.wikipedia.org/wiki/Mansard_roof - Second_Empire

- Old House Journal, “The Mansard Roof and Second Empire Style,” Old House Online, updated Oct. 26, 2018, www.oldhouseonline.com/house-tours/the-mania-for-mansard-roofs

- “What is Induction Cooking?”, Frigidaire, www.frigidaire.com/Collections/Induction-Appliances-Collection/What-Is-Induction-Cooking/ - :~:text=Induction cooking uses electric currents, cooking vessel itself almost instantly.

- John Forger, Owner, Olde Forge Realty, Office: 617-227-6600; Cell: 617-799-5818; john@oldeforgerealty.com