Drainage

1. Drainage elements in the editor

In the roof editor, they are in the Drawing section, in the Drainage group:

• Drain: a point drain, one click inside the roof. A new drain aligns with the other drains; Alt turns snapping off.
• Gutter: a gutter or free drainage edge. Click to set the start and the end; it snaps to the corners and edges of the roof.
• Scupper and Overflow (emergency overflow): they are placed on an edge of the outline, and water flows through them over the edge.

Each separate part of the roof needs its own outlet. A gutter applies only in the part where it is drawn. In a hall, drains lie only on the valleys, see Hall and diverters.

Scupper or emergency overflow

Below the tools there is a list of the placed scuppers and overflows with a Main outlet checkbox:

• ticked: the scupper is a main outlet, the slopes lead to it and it counts towards the drainage capacity,
• not ticked: an emergency overflow, assessed only in the emergency drainage.

Draw gutters parallel to the edge of the roof. The editor marks a skewed gutter and offers Align with grid with a preview of the shift.

2. Manufacturer and type of element

1. In the project cockpit, open the Materials tab, section Hydraulics / drainage.
2. Choose Drain manufacturer and Drainage product type. Only the types the manufacturer has in the catalogue are offered. You do not select a specific size; the drainage assessment calculates it.
3. For a walkable roof, tick Walkable roof (terrace). The assessment then offers only walkable drain versions.
4. In the expandable Emergency overflow section, choose Overflow manufacturer.

3. Drainage assessment

1. Open the Drainage assessment tab. The active roof is assessed.
2. The assessment is not saved; it is calculated from the current data each time you open it. After changing the drains, the manufacturer or the slopes, click Recalculate.

The main drainage shows Area A, Rainfall intensity r, Runoff coefficient C, Design flow Q, Drain capacity, the number of installed and required drains, Min. drains (ČSN) and Minimum sufficient size. The rainfall intensity and the runoff coefficient are fixed standard values.

• Area per drain: with calculated slopes, each drain has its own drained area, and the size is determined by the drain with the largest area. Without valid slopes, the area is split equally between the drains, and the assessment says why.
• Series by waterproofing: in the same size, a manufacturer often has several series for different waterproofing types. The assessment selects the series according to the main waterproofing of the roof. If it does not know it, it calculates with the lowest capacity and warns you.

4. Emergency drainage

An emergency overflow drains only when the drains are blocked. That is why it has its own Emergency drainage assessment block with its own verdict.

• You enter the Runoff coefficient C. Different values apply to emergency drainage than to the main drainage.
• The application pre-fills it from the build-up only if it knows the thicknesses of all layers of the vegetation build-up. Otherwise it waits for your input.
• The block shows Emergency flow Qnot, Overflow capacity and Design head.

What the results mean

• Complies and Does not comply: for a non-compliant result, the application states the number of drains to increase to. You add the drains in the roof editor.
• Cannot be assessed: an input is missing, for example the scale, the manufacturer of the elements or the coefficient for the emergency drainage. The application states what to add and where, and does not substitute anything.
• Not applicable: the roof has a free drainage edge and water drains freely. This is not an error.

The assessment covers the number and capacity of the drainage elements. It does not size pipework. The limits of the outputs are described in the article What FredIQ does not assess.