Terraces over utility rooms are usually made as full terrace roofs with a traditional arrangement of layers.
In a full terrace flat roof, the upper level of the construction board is lowered in relation to the upper level of the raw ceiling inside the building. This is due to the difference in the thickness of the terrace finishing layers and the floor layers on the interior side.
The thickness of the flat roof, which consists of drop spouts, thermal insulation and finishing layers is as a rule 10 – 20 cm greater than the thickness of a floating floor made of 5 cm of polystyrene board i 5 cm of concrete slab.To this you should add a reduction of the terrace area by approx 10-15 cm in relation to the balcony door threshold, enabling the anti-water insulation to be folded over the wall
The difference in the level of the floor slabs results in a different level of ceiling height in the room under the terrace and in the residential interior.
When designing a terrace flat roof, it is important to correctly design the balcony door threshold.
Balcony doors, especially on terraces without a roof, during heavy rainfall, they pose a risk of rainwater penetrating the threshold. For this reason, the recommended solution is to lower the terrace area in relation to the door threshold by one step, which at the same time corresponds to the recommended height of the ceramic tile pedestal around the walls (15 cm). An additional protection is the connection of the step with the balcony door threshold with a galvanized steel lattice platform. Such a platform rests on two steel angles – one attached along the door sill and the other on the edge of the concrete step. Solution, which allows to maintain the same usable levels of the interior and the balcony slab is linear drainage assumed in the thickness of the balcony screed along the threshold of the balcony door.
The roof made of wooden beams above the ceiling sheathing consists of two parts:
• Stropodach pełny z paroizolacją na poszyciu stropu, thermal insulation between wooden beams with a cross-section forming a slope, on which there is a waterproof plywood sheathing covered with bituminous felt as a waterproofing layer.
• Podniesione ponad poziom hydroizolacji wykończenie użytkowe, made of openwork boards on joists with a variable cross-section to compensate for the fall of the solid flat roof plating.
The roof allows you to leave exposed joists, but such a solution significantly increases the level of usable terrace in relation to the level of interior finishing. Handrails, so as not to disturb the waterproofing, are mounted on the external wall of the building.
The passage of the chimney through the flat roof requires careful execution of sheet metal flanges sealing the connection of the flat roof covering with the chimney wall. The flashing should be folded over the chimney wall to the height of the splashing rainwater, tj. about 30 cm. It is also advisable to secure the concrete cap covering the chimney with sheet metal work.
The recommended design solution is to make the chimney base in the form of a reinforced concrete flange connected monolithically with the ceiling slab. The advantage of the proposed solution is the possibility of a simple and reliable folding of the waterproofing insulation on the chimney wall.