Video: Grading On Flat Roofs
2023 Author: Douglas Hoggarth | [email protected]. Last modified: 2023-05-24 11:23
Flat roofing technology involves the creation of a slight slope so that rain and melt water can drain freely into storm systems.
The ways of forming the slope are as follows:
Laying with a slope of the supporting structures themselves (corrugated board or concrete slabs). It is mainly used with slopes from 5 to 10 degrees with pitched and gable roofs.
Lightweight concrete screed with the creation of the required profile. A layer of lightweight concrete of variable thickness creates the required slope. The configuration of draft surfaces can be complex.
Creation of a slope when forming a thermal insulation layer. This method is used when it is necessary to minimize the load on the roof as much as possible. For this, either foam glass or extruded polystyrene foam is used. A standard thermal insulation board is given a variable thickness so that when laid out on a horizontal surface, the required slope is obtained.
Since the first method is carried out mainly during the general construction installation of a building, it is not advisable to consider it as a component of roofing work.
The most common method of forming a slope on flat roofs is a claydite-concrete screed. In fact, this is not even expanded clay concrete, but mainly expanded clay with a small amount of cement and water, which are necessary as a minimum binder when forming this layer. The main advantage of this method is its high manufacturability and low cost. Modern technologies offer new and effective solutions. One of such solutions is the use of polystyrene concrete. Although it was developed in our country about 25 years ago, it has now received a rebirth. Polystyrene concrete refers to lightweight concrete as the main filler, which is polystyrene granules. The surface of the granules is treated to ensure their uniform distribution in the thickness of the material. The combination of insulating material (polystyrene) and concrete creates an optimal combination of load-bearing properties, thermal insulation, sound insulation and fire protection.
Having almost the same cost as expanded clay concrete, polystyrene concrete surpasses it in terms of density, thermal conductivity, and manufacturability.
The main comparative characteristics are shown below:
Expanded clay concrete
Density (kg / m3): 850
Coeffits. Thermal conductivity, W / (m * C): 0.38
Water absorption,%: 10
Density (kg / m3): 150-550
Coeffits. Thermal conductivity, W / (m * C): 0.6-0.18
Water absorption,%: 6
Higher manufacturability of polystyrene concrete is expressed in the following:
It is less laborious when preparing the mortar directly on the construction site.
The equipment for the preparation and delivery of concrete wears out much less, in contrast to expanded clay, which acts as an abrasive.
The surface obtained after pouring is quite even and does not require the creation of a leveling screed. Mashing with a solution is enough.
In the event that the roof area has large dimensions, the reduction in such costs can be significant. The latter method of creating a slope is the most time consuming and costly. It is used in exceptional cases, when the use of a concrete screed, for one reason or another, is not possible.
The most suitable material for this is foam glass. With this installation, the thermal insulation layer:
Forms a monolith in strength that is not inferior to concrete, while remaining lightweight. The average density of foam glass is 170 kg / m3.
It acts as a vapor barrier, preventing moisture from condensing on the underside of the waterproofing layer.
Serves as a root barrier on green roofs.
Among other things, it has stable characteristics over time. There is practically no material aging.