Rooftop and terrace fountains

Rooftop and terrace fountains

Loading, sealing, drainage, vibration control and coordination with the building

A fountain on the roof of a commercial center, a hotel terrace or a public space above a parking lot can play a role in the formation of the architectural identity and the quality of people's presence. The reflection of the sky, the controlled sound of water and the combination of light with the city landscape are the possibilities that these spaces provide to the designer.

In such a project, the fountain is part of the building. The weight of the water is transferred to the structure, the sealing performance affects the spaces below, and the noise of the equipment may be heard in rooms far from the fountain. Therefore, architectural design, structure, facilities and operation should be coordinated from the beginning.

In this chapter, a hypothetical rooftop fountain is explored. Dimensions, weights and calculation conditions are educational; GSO does not constitute a confirmation of the capacity of a building or product specification.

54–1. Application scope and problem definition

The principles of this chapter apply to several types of projects:

• Bam fountain and roof garden;

• Fountain on the terrace of the building;

• Pool and fountain on the roof of the parking lot;

• The fountain of the square or the area under which there is a built space;

• Fountain on the high platform or the middle floor of the building.

First, it should be determined what space is under the fountain. A leak above a service warehouse, electrical room, shop or hotel room does not have the same consequences. This difference affects the choice of sealing details, leak detection and repair access.

In the existing building, the review of the plans should be completed by knowing the actual condition of the structure, previous changes and the route of the facility. The capacity of the roof cannot be deduced from the number of floors, the appearance of the beams or the experience of a similar building.

54–2. Choosing the shape of the fountain suitable for the roof

In the conceptual stage, several options are comparable:

Shallow depth can reduce water weight, but must be compatible with equipment requirements and display quality. Also, choosing a dry fountain does not mean removing the weight of water; Part of this weight is transferred to the tank and the grid under the floor.

For example, Crystal Fountains introduces integrated basins, drain fittings, and low-rise pedestals in its line of custom fixtures. These features can be useful in solving geometric constraints, but confirmation of installation on a specific roof requires independent investigation. Crystal Fountains custom equipment ^[349]

54–3. loading map; Beyond the weight of water

Before finalizing the placement, a loading plan must be prepared. This map shows the location, amount and how to transfer the load of each component.

The main ones are:

• The water in the pond is at the normal level and the highest possible level;

• Pond body, cover, stone and decorative components;

• Balance tank in different situations;

• Pump, filter, board and chassis;

• Pipes full of water;

• maintenance people and equipment;

• materials and parts accumulated during implementation;

• Environmental loads and building load combinations.

Average load is not a substitute for checking the load transfer path. An assembly of a certain weight may be placed on a wide surface or carry the same weight from several small supports to the ceiling.

The upload should also cover the status of repairs; For example, the location of the removed pump and handling equipment next to the tank can create conditions different from normal operation.

54–4. Calculation of water weight and sensitivity to depth increase

Consider the following hypothetical pool:

Pond area:

$A=6\times 2=12m^2$

Water volume in normal condition:

$V=12\times 0.18=2.16m^3$

Assuming the density of water is 1000 kg/m3:

$m=2160kg$

Load caused by water per unit area:

$q=\rho gh$

$q=1000\times 9.81\times 0.18=1766N/m^2$

Therefore:

$q\approx 1.77kPa$

This amount is only water load.

If the depth reaches 28 cm:

$V_{\max }=12\times 0.28=3.36m^3$

An increase of ten centimeters in depth in this pond creates 1200 kg of additional water.

In general, every centimeter increase in water depth adds about 10 kilograms of mass to every square meter of pond surface. Because of this, the overflow level is not a purely architectural detail.

54–5. Calculation of the total load of the tank and the local load of the tank

To continue the example, suppose:

• Mass of body and tank cover: 900 kg;

• Mass of equipment and fixed components related to the pool: 360 kg.

These values are only calculation assumptions.

Total mass in normal state:

$m_{\mathrm{کل}}=2160+900+360=3420kg$

The equivalent average load on an area of 12 square meters:

$q_{\mathrm{متوسط}}=\frac{3420\times 9.81}{12}\approx 2.80kPa$

Now let's check the balance tank with the following specifications:

Mass of filled tank:

$m_t=1200+180=1380kg$

The average load is equivalent to:

$q_t=\frac{1380\times 9.81}{2}\approx 6.77kPa$

Despite the smaller volume, the tank in this example creates a higher average load per unit area.

This number is also not the actual pressure under the foundations. If the tank is supported, the reaction of each support, the dimensions of the support plate and the behavior of the roof should be checked separately. The numbers in this section also do not include coefficients and load combinations of structural design.

54–6. Placement and coordination with the structure

The structure coordination output must be visible on the map:

• The authorized location of the pond and tank;

• Type and location of supports;

• Reactions on the structure;

• limitation of moving equipment;

• openings and passage of pipes;

• Harness details and movement seams.

Placement near a beam or column may be appropriate in a design, but is not a general rule for verifying installation location. The load transfer route should be checked in the same building.

The rise and movement of the structure is also important. Changing the level of the edge of an overflow pond can make the water distribution irregular; The relative movement of two parts of the building may also damage the rigid connection of the pipe.

The passage of the water fountain or pipe through the moving seam of the building must have specific details. Covering the seam with rock or the body of the pond does not determine its performance.

54–7. Pool sealing and roof protection

In these projects, two tasks should be clear:

1. Keeping water inside the pond; 2. Building protection against water penetration.

How to provide these two tasks depends on the structure of the roof and pond. In designs that have several layers of protection, the space between the layers should also be checked in terms of water leakage and the possibility of detecting leaks.

The WBDG Guide for Green Roofs emphasizes protection of the waterproofing layer, drainage and leak detection capability. These principles are useful for coordinating the fountain with the roof, although the details of the green roof should not be directly extended to the fountain basin. Guide to green roofs WBDG ^[350]

The inner lining of the pond must be approved for submersion and water chemistry conditions. For example, Tremco introduces specific systems for fountains, waterfalls and reflecting pools; The selection of the product should be accompanied by the compatible infrastructure and details of the same system. Fountain sealing systems in Tremco ^[351]

Sensitive points in the executive plan include floor-to-wall connection, pipe penetration, equipment base, built-in light, overflow, and the end of the sealing layer.

54–8. Leak detection and reaction command

For a water feature above a built space, it must be determined how the leak is revealed and what happens afterwards.

A suggested logic to consider in design:

Stopping the pump does not remove the water stored in the tank. For this reason, the emergency evacuation route and the possibility of compensatory water cutoff must be known in advance.

The sealing test should also be planned before covering sensitive points. The WBDG emphasizes that in the dewatering test, the water weight should not exceed the capacity of the structure and the test method should be compatible with the existing structure. Roof sealing test considerations

54–9. Return volume during shutdown

Suppose in the sample circuit, when the pump stops:

• The water level of the pond drops by 25 mm;

• 30 meters of pipes with an internal diameter of 50 mm are discharged;

• 25 liters of water returns from other components.

Return volume of the pond:

$V_1=12\times 0.025=0.300m^3$

Pipe volume:

$V_2=\frac{\pi D^2}{4}L$

$V_2=\frac{\pi (0.05{)}^2}{4}\times 30\approx 0.0589m^3$

Total returned volume:

$V_r=0.300+0.0589+0.025\approx 0.384m^3$

Therefore, the tank should receive about 384 liters of return water in this situation.

If the water volume of the tank in working mode is 0.6 cubic meters and its volume up to the defined maximum level is 1.2 cubic meters:

$V_{\mathrm{پذیرش}}=1.2-0.6=0.6m^3$

In this simple calculation, the acceptance capacity is greater than the return volume. However, the volume occupied by the components, surface fluctuation, compensating water flow and other inputs must be considered in the actual design.

The return volume must be calculated with the actual discharge path and the possibility of siphoning; The mere existence of a one-way valve does not replace this investigation.

54–10. Precipitation, overflow and discharge

Pond overflow, fountain service discharge and roof drainage have different tasks. Their connection should be clear in the facility map.

For an educational example, suppose:

• Effective level of receiving precipitation: 40 square meters;

• Hypothetical rainfall intensity: 80 mm/h;

• Runoff coefficient for this calculation: 1.

Rainfall input flow rate:

$Q_r=iA$

$Q_r=0.08\times 40=3.2m^3/h$

$Q_r\approx 0.889L/s$

If compensation water is also entered at the same time with a flow rate of 0.2 liters per second:

$Q_{\mathrm{ورودی}}\approx 1.089L/s$

This number is the input flow of the hypothetical scenario; It does not determine the diameter of the pipe or the ultimate capacity of the overflow.

Design rainfall intensity should be taken from site data and project criteria. The height of the water on the spillway, the pipe route, the exit conditions, the possibility of clogging and the emergency route should also be checked.

The empty space of the tank is not a substitute for the sustainable drainage of precipitation. Also, the water collected on the roof should not enter the fountain circuit without checking the quality and volume balance.

54–11. Building height and pump head

The height of the roof from the ground is not necessarily added to the fountain circulation pump head.

If the tank, pump and fountain are all on the roof, the head of the circuit is obtained from the difference in the levels of the same circuit, the nozzle requirement and the path drop. If water is transferred from a tank on the lower floors to an open fountain on the roof, the height difference between the two will be included in the calculation.

For the hypothetical circuit:

with a flow rate of 12 cubic meters per hour and a hypothetical total efficiency of 55%:

$P=\frac{\rho gQH}{\eta }$

$P=\frac{1000\times 9.81\times (12/3600)\times 8}{0.55}\approx 476W$

This value is the estimated input power at the assumed point. Pump and motor selection must be completed with the actual curve, suction conditions and all operating modes.

54–12. Sound and vibration control

Two paths of sound transmission should be considered separately:

Aerial route: the sound of water falling and the operation of equipment reaches the surrounding spaces.

Structural Path: Vibration is transmitted from the foundation, pipe or connection to the building.

Mason, in his guide to flexible fittings, mentions the transmission of pump pulsations in the pipe network and the creation of noise or vibration. Therefore, vibration control is not limited to placing a piece of rubber under the pump. Mason Flexible Fittings Guide ^[352]

In the design, the weight of the set, the speed of work, the hardness of the support, the pipe connections and the necessary restraints should be checked.

The sound acceptance criterion must also be defined in the sensitive area; Like the room under the fountain or the adjacent terrace. The test alone next to the pump does not give a complete picture of the sound transmission to the building.

54–13. Wind, lighting and general use

On the roof, the wind check should pay attention to the path of the droplets and their exit from the building. The proper height of the fountain cannot be determined only from the dimensions of the pond.

In the control program, the state of strong wind, blackout, level drop and sensor failure should be predicted. The distance of the fountain from the edge of the roof, the way of commuting and the placement of furniture should also be in harmony with the spraying area.

The lighting of the fountain should be checked from the spectator's place, the adjacent building and the spaces below. Access to lights and cable connections should not depend on wide opening of the seal.

A decorative fountain and an accessible fountain for people do not have the same requirements. The user must be clear from the beginning; Shallowness of a pond alone is not a license for interactive use.

54–14. Transportation, repair and replacement of equipment

For each main part, the initial entry and exit route at the time of replacement should be specified.

The important executive questions are:

• Does the piece pass through elevators and doors?

• Is there a space to open the filter and take out the pump?

• Where is the removed piece temporarily placed?

• How is its weight transferred to the structure during transportation?

• How long does the service operation limit public use of the roof?

A water feature that can only be repaired with a crane should reflect this need in the operation plan and cost estimate.

The service valve should also be designed based on the dimensions of the part and the movement required for its exit; A technician's access to the screws does not mean that the assembly can be replaced.

54–15. Delivery procedures and responsibilities

Delivery should be done in several stages:

In the contract, the responsibility of connection between the pond, sealing of the building, drainage and facilities should be clear. The general phrase "sealing with another contractor" without a specific plan and scope is not sufficient for delivery.

The final documents must show the user the normal and maximum water level, the limitation of moving the equipment and the evacuation method.

54–16. Suggested images for layout

Figure note from the source manuscript

Picture 54-1: Fountain in the roof space

Select an image from the GSO archive, if available, that shows the fountain, the seating area and its relationship with the building. The location of the project and the type of structure should be mentioned only based on documented information.

*Subtitle:* "The coordination of the fountain with the landscape, the path of movement and the general use space of the roof."

Figure note from the source manuscript

Figure 2-54: Conceptual section of the pond and roof

In one section, the pond, the support, the sealing layers, the leak detection path and the bottom space should be shown. The order of the layers should be adapted to the actual system of the project.

*Subtitle:* "Coordination of water storage in the pond with building protection and maintenance access."

Figure note from the source manuscript

Figure 54-3: Comparison map of pond and reservoir load

The 12 square meter pond and the 2 square meter tank of the example should be drawn side by side. Average loads of 2.80 and 6.77 kilopascals should be inserted and the words "educational calculation; without verifying the capacity of the structure" will appear on the picture.

*Subtitle:* "A smaller tank can load more per unit area."

Figure note from the source manuscript

Figure 54-4: Circuit in on and off state

In two schematics, the level of the tank during operation and after water return should be displayed. The path of overflow, compensation water and service discharge should also be clear.

*Subtitle:* "The control of the return volume and the level of the tank is part of the design of the fountain on the structure."

The final file of this fountain should allow the building manager to identify the load bearing location, possible leak path, stop and drain method, and equipment replacement method without relying on the memory of the operators.