How a penthouse renovation differs and what it costs
A penthouse differs from an ordinary flat in three ways: the terrace, the roof directly overhead and the loads on the floor slab. We price the interior on the same tiers as a flat: Basic from €1,000/m², Standard from €2,000/m², Luxury from €3,000/m², excluding VAT. The terrace gets its own lines in the quote, because it involves waterproofing, drainage and outdoor materials.
We confirm exact scope and price after a site visit and measurements. With a penthouse this matters more than usual: until the old terrace tiles come up, nobody knows what state the membrane is in.
The terrace: what to check before designing
Legal status comes first: a penthouse terrace is often also the building’s roof, meaning a shared element with private use. That decides who pays for waterproofing and whether the community must agree. The answer is in the title deed and the building’s statutes.
Then the technical side: falls towards the drains, the number and size of outlets, the threshold height at the living-room door, the condition of the parapets. The most expensive mistake is laying beautiful new tiles over an old membrane of unknown age. One winter later there is a stain on the ceiling of the flat below, and the tiles come up again along with new waterproofing.
General rules for terraces and roof waterproofing are covered in separate guides. The point here is that terrace decisions come before interior ones, not after.
Loads on the slab
Penthouse terraces attract the heaviest items: hot tubs, large planters with trees, a soil layer for lawn, thick stone paving, a glazed pergola. A planter with an olive tree and wet soil weighs hundreds of kilos; a filled hot tub with people in it, more than a tonne.
The slab of an old building was not designed for that. Before ordering anything heavy, a structural engineer checks the loads. Sometimes the fix is simple: put the planters around the perimeter, over the load-bearing walls. Sometimes the hot tub has to go. Better to find out on paper than on delivery day.
Summer heat and winter cold
Only the roof sits above a penthouse, so the ceiling heats up in summer and heat escapes upwards in winter. You can insulate from inside, in a suspended ceiling, or from outside, as part of a new roof build-up. Inside is simpler but costs height, and some penthouses already have 2.5 m ceilings. Outside works better, but it is work on a shared element and a conversation with the community.
Add three things to the insulation. Ducted air conditioning in the same suspended ceiling, so it is not opened twice. Solar-control glass on large south and west windows. External awnings or louvres: they stop the sun before it reaches the glass, whereas indoor curtains act once the heat is already inside.
What the community and the ajuntament must approve
Anything visible from the street or that changes how the roof looks almost certainly needs community consent and a permit from the ajuntament: glazed pergolas, enclosing part of the terrace, new openings, AC units on the facade. In a listed building, even more so.
The permit type and timescale are confirmed with the ajuntament for your address. A practical tip: design the interior so it works without the pergola too. If approval drags on, the indoor works do not have to stop.
Top-floor logistics
Everything has to go up to the top floor, and the lift in an old Eixample building takes three people. Large glass panels, long worktops and outdoor furniture go up by crane or external hoist, which needs a pavement occupation permit. We check dimensions before ordering: a panel that fits neither the lift nor the stairs becomes a project of its own.
We protect the lift and entrance, keep noisy work to permitted hours and take rubble out on a schedule agreed with the property manager.
Next step
Tell us what you have in mind: interior only or the terrace as well, and whether there are heavy items like a hot tub. Attach the floor plan and photos of the terrace. We reply within an hour, come to measure and prepare a quote with the terrace as a separate block. We run the project in Spanish and Russian, with one person responsible from start to handover.