Flat roof vs pitched roof: which to choose for a house in Batumi

In Batumi, the flat roof vs pitched roof question is decided by water. Downpours here are heavy, and a roof has to shed a large volume of water into the drainage in a short time. A pitched roof does this on its own, while a flat roof needs accurate slopes, working outlets and a backup route in case of a blockage.

Downpours: where the water goes

On a pitched roof, water runs down into gutters and downpipes. Its weak spots are well known: valleys, where two slopes meet, and junctions with walls, chimneys and roof windows. Water gathers into a stream there, so these details are the first ones we check and photograph.

On a flat roof, water flows to the outlets along a slope formed with screed or tapered insulation. If the slope dips somewhere, a puddle forms, and water sits on the waterproofing after every rain. In a downpour, leaves can block an outlet, so we build emergency overflows into the parapet: water escapes through them even when the main drainage cannot cope.

Flat roof vs pitched roof: leaks and repairs

A leak in a pitched roof can usually be seen from the attic, and the spot is found quickly. On a flat roof, water can travel through the layers of insulation and come out on the ceiling far from the defect. The repair then starts with a search, and sometimes with opening up part of the roof build-up.

That is why we build a flat roof as a system, checking each layer before the next one goes on. We take the waterproofing up the parapets and walls and reinforce the junctions, and before laying tiles or gravel we flood the roof to check for leaks. We photograph each layer before it is covered, and these photos stay in the handover file.

Roof terraces and equipment

A flat roof can serve as usable space, and that is its strength. On a house in Makhinjauri or Gonio, the roof becomes a terrace with a sea view, and also a place for solar panels, water heaters and outdoor air conditioning units. A roof that people use needs a protective layer over the waterproofing, a railing and access from the stairs.

A pitched roof has its own usable space underneath: an attic room or storage space. By the sea we always ventilate the space under the roof through the eaves and the ridge, otherwise moist air condenses under the covering and soaks the insulation.

Wind, salt and earthquakes

Wind from the sea tears roofing off first at the edges and corners. On a pitched roof that means the eaves and gables, on a flat roof the edges of the membrane and the parapets, and in these places we put the fixings closer together. By the sea we use metal flashings, trims and fixings that are stainless or have a protective coating.

For seismic safety, the mass at the top of the house matters. A terrace with tiles, screed and planters is noticeably heavier than a light covering on rafters, and the structural engineer allows for it when designing the floor slab and the frame. We fix the rafters of a pitched roof to a ring beam, so that in a tremor the roof moves together with the house.

What the roof is made of

For a roof terrace, an inverted roof works well: the waterproofing membrane lies under the insulation, and on top there is a ballast of gravel or tiles on pedestals. This protects the membrane from the sun, temperature swings and accidental damage, so it lasts longer. The waterproofing itself is a polymer membrane or two layers of torch-on bitumen-polymer sheets, as the design specifies.

For a pitched roof, the covering is a separate choice: metal roof tiles, asphalt shingles or clay tiles. Clay tiles are noticeably heavier than the others, and in a seismic zone their weight goes into the calculations for the rafters and the frame. Light coverings largely remove this issue, and by the sea they are compared on corrosion and on noise in the rain.

Upkeep and the cost of the work

A flat roof needs looking after: the outlets and overflows are cleaned after the leaves fall and after heavy storms, and once a year the seams and junctions are inspected. If you live abroad, agree in advance who will do this. A pitched roof is more forgiving if an inspection is missed, although its gutters also fill up with leaves.

In terms of cost, the two are comparable. A flat roof gets more expensive when a full terrace is built on top, and a pitched roof when it has a complex shape with valleys and roof windows. What affects the estimate most is the shape of the roof, a terrace on top and the number of junctions.