CONSTRUCTION OF ROOFTOP GREENHOUSES

By Nicolas Brulard (Fermes de Gally) and Ismaël Baraud (CSTB)

INTRODUCTION

This chapter focuses on the construction works of the building and the greenhouse. It is intended to guide users toward the achievement of a project. It provides explanations about the supplemental chapter required in the Special Technical Specifications (STSs). It suggests a glossary and terms used to specify the greenhouse description. It is aimed for architects, urban planners, building contractors, etc.

According to the rules and regulations of each country, the method and the documents written by each stakeholder should be adapted to comply with usual local methodology and rules.

Bellow: Construction site of Chapelle International, Paris (France)

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In France for example, the first step of a project consists in writing a project outline draft (POD). This document describes the general purpose of the project.

Then a project final draft (PFD) is written. This document describes the technical solutions and provides details about the project budget.

Then STSs are written. These documents describe the supply and execution of each part of the building, with the product specifications, the methods of execution, performances, and specific purposes.

In addition, STSs are a contractual document between the project manager and the owner and are specific to each operation. Their full drafting is the responsibility of the project manager, both in form and content.

The present section is not intended to provide a "typical" description of a rooftop greenhouse (RTG) structure, which is the subject of a special section in this document.


There exists a common basis as to how to write each group of specifications for the construction of a building. RTG construction should therefore comply with these rules.

Five main execution blocks can be distinguished for the construction of RTGs

  • the structural work part, related to masonry, preparation of walls, ceilings and structural anchors, accesses (lifts, stairs)

  • the waterproofing package, related to the flat roof work, ensuring the enclosure, and covering of the underlying building

  • the RTG structure batch, related to the structure bearing the greenhouse and its envelope, including climatic regulation (shading, openings, walls, etc.)

  • the plumbing batch, related to incoming and outgoing fluid equipment and networks, and their connection with the building networks

  • the electricity package, related to control devices and electrical supply / communication networks, and their connection with the building networks

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FLAT-ROOF DIAGNOSIS

The flat-roof diagnosis provides information about the existing structure and about the composition of the structures ensuring the closure and coverage, and give a description of all the preparation works (foundations, braces, refurbishment, shadowing, load, wind exposure, etc.). The STS should

  • describe how to perform this diagnostic analysis (documentary analysis, sampling, tests, calculations)

  • describe which document will approve the feasibility of the works (report, statement, technical approval delivered by authorities, etc.)

  • indicate the overload hypothesis and descent of loads on the building structure, and what measurements need to be checked

  • calculate the excess capacity of the foundations

  • calculate the risk of uplift wind load and the constraints applied to the RTG structure

EXTRA PREPARATION WORKS

The STS will indicate all the extra preparation works related to the greenhouse construction. It will cover all security aspects (scaffolding, safety) and supply chains, a place for storage, crane installation, waste management, energy supply for the construction works, facilities, etc.
The enabling works will also include modifications on the roof, e.g. removing tiles, pedestal and slab protection or granulate, waterproofing reinforcement, creation of a new access, displacement of existing equipment (ventilation outlet, rainwater inlet pipe) on the roof, drilling for pipes or cable sheaths, creation of concrete pillars or slabs, methods of mechanical anchoring of the greenhouse to the roof, etc.

ACCEPTANCE OF THE PREPARATION WORKS BEFORE THE GREENHOUSE CONSTRUCTION

The STS will specify all the steps of the works that require acceptance before the greenhouse structure is built.

In case of claims, corrective actions will have to be started before starting to build the RTG structure.

  • Warrant protection

  • Signature of the RTG manufacturer

GREENHOUSE STRUCTURE AND ENVELOPE WORKS

The STSs will take specific conditions into account when the greenhouse is built on a roof as compared to a traditional greenhouse built on the ground.

Bellow: The structural anchoring of a greenhouse on an existing roof is specific

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INTERIOR LAYOUT OF THE GREENHOUSE AND PRODUCTION DESIGN

The STSs should highlight specific organisation elements linked to the construction of a greenhouse on a roof. They will clearly focus on technical constraints and the non-accessible zone. Some of these specific elements are:

  • the technical floor

  • energy transfer connections with the building

  • a safety shields

  • pillar protection

  • kick rails

  • signage, user’s circulation, access management

  • training sessions

  • localisation of anchoring points and hanging points

  • selection of contractors

  • localisation of water supply pipes, heating and air supply pipes

Bellow: The interior design will define the localisations of the different energies.

e.g.: a greenhouse for growing tomatoes on culture bags, low temperature heating on the ground and suspended gutters.

Picture taken by GROOF team when visiting BIGH farms at Anderlecht, Belgium

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