Design and selection of materials for an attached greenhouse

In this chapter, the authors have sought to provide the reader with practical recommendations for greenhouse construction, as well as for selecting and purchasing building materials. This is not an easy task, since the recommendations provided in this book cannot resolve all issues concerning greenhouse construction. There are many different types of greenhouses, which differ from each other in shape, size, functional operation, and appearance. Residential houses are also diverse and have varying conditions for the construction of greenhouses within them.

Here, two simple types of greenhouses will be examined. One of them is applicable to both new and old small houses located in favorable climatic conditions (see Ch. 4). The second type can

8— 293 113 be used for new and especially old multi-story buildings, in which loggias are easily converted into greenhouses if they are equipped with a glass wall.

This book covers methods for implementing greenhouse design projects, taking into account the type of soil, building materials, etc. A number of recommendations are intended not for professional builders, but for a wide range of people who perform construction work with their own hands.

A greenhouse must meet many requirements applicable to residential buildings. For example, its frame must withstand its own weight and the weight of snow, as well as loads created by wind exposure. The greenhouse foundation must be constructed appropriately, and its appearance should harmonize with the look of the residential house. In addition, the greenhouse must meet a number of functional requirements discussed in this book. A greenhouse is relatively small in size and quite simple in design. However, it is a critical part of a building, as it is subject to special requirements, for example regarding temperature and humidity. To avoid potential mistakes, the authors recommend seeking the help of qualified specialists when designing and building a greenhouse.

First of all, it is necessary to carry out preparatory work thoroughly. To do this, one must study initial climatic data, investigate soil characteristics, and evaluate the possibilities of connecting the greenhouse to the residential house. It is also advisable to determine the purpose of the greenhouse, which may be multi-purpose. During the design phase, various alternative options should be compared and the best one selected. It is necessary to draw up a detailed project implementation plan, prepare a list of required materials indicating their cost, etc. Construction work should only begin after the owner is able to visualize the greenhouse in their mind.

A greenhouse attached to a private house

Here, a small typical private house available on the Finnish market (Kestilän Talotehdas company) will be examined. The house has 4–5 rooms, includes a kitchen and a sauna unit, as well as a small room used for household chores and watching television. The house has a narrow frame and a gable roof with a 1:3 pitch, which is typical for Finland. The house stands on a concrete foundation and has a timber frame. This is a modern small private house adapted for northern climatic conditions.

The house design provides for the possibility of attaching a greenhouse, which can be implemented through direct delivery or construction at a later stage based on the "do-it-yourself" principle.

The latter method is described in detail in this book.:

Connecting the greenhouse to a private house and its construction. Usually, a greenhouse is positioned on the south side of a private house, designed so that a kitchen, recreation room, or multi-purpose room is located behind it, with which the greenhouse is best combined in terms of its functional characteristics. The greenhouse can be rectangular in shape or follow the slopes of the house walls at a 45° angle. The authors have chosen the rectangular greenhouse option as the simplest and most typical.

Wooden structures were used as the construction material for the house frame, as timber is easy to work with and suitable for "do-it-yourself" construction or community work projects. At the same time, it is taken into account that unified modular measurement systems are adopted in the construction industry, and ready-made building structures, such as windows and doors, are available on the market.

Laying the foundation. Corner piles and "line trestles". In Finland, as a rule, it is necessary to obtain a building permit for a greenhouse attached to a residential house. In this process, representatives of the authorities perform the marking of the greenhouse corner points

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Fig. 74. An individual residential building to which an extension is being attached

Fig. 76. Corner piles and "line rails" (at the site of greenhouse layout) directly on the plot by driving in the piles. They mark the height of the floor level above the ground on the piles. In cases where the owner performs such corner point layout themselves, the measurement should start from the outer wall of the building. For

Fig. 77. Shallow foundations under favorable soil conditions, it is necessary to set a board at an angle of approximately 90° relative to the plinth of the building. The locations of the corner points are determined by the method shown in Fig. 76. Then the piles are driven into these locations, and their positions are checked by ensuring that the tangents a and a' are equal to each other.

After this, it is necessary to build "line rails" on which marks for the outer lines of the house plinth should be made, for example, by driving in two stakes, which can then be connected using strings.

Concrete base (foundation). If the soil has an average bearing capacity (20.5 mgf/cm²) and is homogeneous in its composition, it is permissible to construct the foundation by pouring concrete supports. These supports are then buried to a depth of approximately 30 cm with a width of about 30 cm. After this, the bottom of the pit for the support is leveled by adding sand or crushed stone. If bedrock is close to the soil surface, the pit for the supports should be dug down to the bedrock, and then the surface of the rock base should be thoroughly cleaned.

After this, it is necessary to construct formwork for the foundation footing using boards. Here, the earth can be used as a mold, but the formwork for the upper part of the support must be made of boards so that the horizontal edges of the concrete support are even; with their help, a clean upper surface of the support can be obtained by leveling it with a board. In this case, it is not

Fig. 78. Pile foundation construction using railway rails as piles

1 — rails or steel beams; 2 — pressure-treated wooden timber; 3 — minerite sheet; 4 — plastic sheet (foam plastic)

"flagpole" 1 — post greenhouse frame; 2 — pressure-treated wooden piles; 8 — adjustable fastener. Do not forget about the connecting strings and steel fasteners.

It is necessary to ensure that the boards in the formwork will not move during the concrete pouring. The dimensions and height mark should be checked once more to ensure they exactly meet the requirements, after which the form should be filled with concrete. The latter is pre-ordered from the nearest concrete plant.

Simple pile foundation for greenhouses

When building on soft soil, it may be necessary to use piles. The most reliable method is using a concrete pile for driving or burying. Both methods require the use of expensive heavy equipment, which can damage the site and cannot always be delivered to the construction site. Therefore, two simple and cheap methods of foundation construction will be considered here. Nevertheless, it is recommended to consult a specialist before starting work.

It is recommended to use steel rails or similar profiles, or pressure-treated railway sleepers as piles. The advantage of steel profiles is that they can be driven into the ground more freely. It is necessary to use sufficiently long piles to reach a depth below the permafrost line or to reach soil with higher bearing capacity.

Driving piles is a rather labor-intensive process. Sometimes, when driving a pile, it hits a stone, due to which work is stopped or the direction of the pile penetration is changed. Therefore, when designing the plinth, it is recommended to provide for:

• a sufficient margin in the lateral direction for driving in soils with a thick layer of clay;
• the possibility of correcting (adjusting) the pile in the vertical direction (flagpole principle) in the absence of dense bearing soil.

Concrete slab foundation

Another, more reliable, but also more expensive method of building a foundation in soil with unsatisfactory bearing capacity is the so-called concrete slab foundation method. It consists of manufacturing a relatively thick reinforced concrete slab, with the help of which the load can be distributed over the entire area of the greenhouse premises.

In case of unfavorable (loose) soil, replacement of its mass may be required. The soil mass under the greenhouse is completely removed to another place and replaced, for example, with crushed stone or "leca" type gravel; as a result, a layer of "new" soil is obtained, which has good thermal insulation and is anti-frost. Another method involves laying styrox sheets (for example, 10 cm thick) on a layer of crushed stone and manufacturing a reinforced concrete slab by pouring concrete onto the styrox sheets.

Choosing a method for building a foundation is sometimes difficult, for example, for clay soil and especially for soil that varies with depth (consisting partly of rock and partly of clay). In these cases, it is recommended to seek help from an experienced builder or engineer. Errors made during foundation construction often lead to damage that, in some cases, cannot be corrected.

Construction of the plinth part. The plinth part

Fig. 80. Various structural solutions for plinth construction: a — shallow foundation and concrete plinth; b — deep foundation and cast plinth using Leca gravel; c — shallow foundation and light-structure plinth; 1 — concrete (reinforced concrete); 2 — anti-frost sheet; 3 — drainage pipe; 4 — steel fasteners; 5 — Styrox sheet or equivalent material; 6 — pressure-treated timber; 7 — Minerit sheet can be built on a foundation shoe in one of the following three ways:

by pouring concrete, using rigid thermal insulation sheets on the inner side (in this case, it is necessary to install lifting steel hooks and binding wire in the appropriate places);

by laying cast blocks with Leca gravel, which have high load-bearing capacity and good thermal insulation properties. If such a wall made of cast concrete blocks turns out to be high, it is necessary to use reinforcement to strengthen the wall (soil pressure);

by using pressure-treated timber with subsequent thermal insulation, for example, using Styrox sheets and covering with Minerit sheets or high-strength sheets.

The same methods are suitable for the construction of pile foundations.

The choice of method depends on the skill of the builders, building materials, the type of soil, the foundation construction method, as well as the type of plinth

The plinth part covered with Minerit sheets and the concrete plinth can be left unpainted and untreated if the work is performed cleanly and the gray color is acceptable to the client. The plinth part built by laying cast concrete blocks or, for example, sand-lime bricks, is recommended to be covered with a layer of plaster and painted. When choosing paint, it is necessary to ensure that it adheres firmly to the surface of the greenhouse plinth and will not peel off (a problem

Construction of the frame. In the greenhouse version considered here, a wooden frame was chosen. Both horizontal and vertical frame structures can be made of standard lumber with a sawn or planed surface, as the greenhouse has a low height and short spans.

If the greenhouse is two-story and has larger spans (for example, when a house roof is converted into a greenhouse), then glued beams can be used in vertical, horizontal, as well as in through (lattice) structures. Furthermore, combined beams with nailed and glued connections (for example, of the type

When choosing frame connections, it should be remembered that humidity in the greenhouse can be very high, so it is necessary to take measures to ensure that wooden and especially glued structures withstand maintenance and strength factors, which led to the replacement of lumber with light metals. However, for greenhouses built for individual homes, lumber is a perfectly suitable construction material, and the authors recommend using it

When building the greenhouse frame, metal profiles can also be used. However, the use of metal structures requires high qualifications from builders and the use of special tools. The use of steel is particularly undesirable due to its susceptibility to corrosion.

Lumber and its treatment. Pressure-treated lumber is a reliable and durable construction material, but it is expensive and has a greenish tint, which can give structures an unpleasant appearance. The authors of the book recommend using pressure-treated lumber if the wood surfaces can be stained dark or painted. The Teknos Maali company also offers "Herba" white protective paint, which protects wood from fungi and mold and can be used as an anti-corrosion agent.

If it is necessary to preserve the natural color and texture of the wood on the surface of wooden structures, non-deciduous lumber with protective linseed oil treatment should be used. True, recently other methods of pressure treatment have been found that do not change the natural color of the wood. It should be noted that the greenish tint of wood after salt solution treatment fades over time.

The use of pressure-treated lumber is safe for growing plants, despite the fact that the wood is impregnated with toxic substances. The only place where extreme caution should be exercised is the base on which the plants are grown. Plant roots should not come into contact with pressure-treated lumber.

For vertical structures (posts and joists), battens and thick boards with standard sizes of 50x100 or 50x125 mm can be used. After planing, their dimensions are reduced to 45x95 and 45x120 mm, respectively. For roof beam structures, squared timber with standard sizes ranging from 50x150 to 50x200 mm can be selected, depending on the span lengths and spacing.

The authors recommend compiling a list of necessary lumber, which should include data on their standard sizes and processing methods, as well as the dimensions of lumber for individual applications and their total quantity. It is necessary to clarify the possibility of purchasing lumber in advance, as different suppliers have different stock levels. It is also recommended to contact timber trading companies and coordinate with them not only the costs of the lumber,

but also the following specific issues:

assortment and quality of lumber (BT 216.01); thickness and width of sawn (planed) materials (KT 210, 51/210.61);

quantity of materials in meters, potential losses during sawing, and total losses (10—20 %);

This ensures the smooth and cost-effective supply of the most suitable lumber within the specified timeframes.

Frame construction. First, roofing felt or a strip of butyl rubber is laid on the leveled upper surface of the plinth. In this process, it must be ensured that moisture rising from below through the plinth (capillary action) does not reach the lumber.

After that, it is necessary to mark the locations for potential anchor bolts or other hardware on the horizontal wooden spans, drill the necessary holes in them, and treat the surfaces with an anti-rot agent if pressure-treated lumber is not available. Then, install the finished wooden structures onto the plinth surface. It is necessary to re-check the main dimensions and then mark the positions of the vertical posts (battens) on the horizontal spans. Next, securely attach the horizontal spans to the plinth and check their horizontal position using a spirit level or plumb line.

After completing the precise leveling, the vertical battens can be cut to the established dimensions and their connection points treated. It is easier to perform sawing of battens and processing of connection points while on the ground than while standing on scaffolding or ladder rungs. When

Fig. 81. Installation of a horizontal beam onto the plinth 1 — anchor bolt; 2 — washer and nut (countersunk); 8 — waterproofing spacer. If these structures are pre-cut to the finished size, the entire work will have to be redone if deviations from the established dimensions are found at the connection points (residential house, plinth). Therefore, many carpenters attach vertical posts to horizontal spans first by toe-nailing, and then bring these posts into a vertical position by nailing diagonal boards on both sides of the posts. Then they verify the dimensions, mark the sawing locations, and, after ensuring that all structural dimensions exactly meet the requirements, they perform the sawing.

Now the vertical posts and upper spans (beams) can be connected, securing their set positions by nailing at an angle. The assembly methods for wooden structures described above can also be used for installing structural roof elements. Beams of the required length can be prepared on the ground and only after that mounted in their places. In the example under consideration, the placement of the beams corresponds to the set positions of the vertical posts, with the distance between adjacent posts being quite large — 1.5 m. This distance can also be different. All dimensions and distances should be chosen so as to allow the use of glass or organic glass covering. Good results have been obtained with distances between posts that are multiples of 30 cm (3 M). It is also necessary to remember that the dimensions of many thermal insulation materials are determined based on the design, in which distances of 60 cm (6 M) are adopted.

The beams are positioned on the facade wall side of the greenhouse directly above the horizontal span and connected to the roof structures (beams) of the residential house or placed on top of the horizontal beam, which is fixed along the facade side of the house.

Following Fig. 82 Two methods of connecting vertical and horizontal greenhouse structures

1 — horizontal beam 50x125 mm; 2 — vertical timber 50x125 mm; 3 — beam 50x125 mm; 4 — ceiling squared timber 50(150—200) mm; 5 — steel fixing bracket or equivalent part; 6 — galvanized steel; 7 — galvanized bolt or equivalent part

Vertical and horizontal structures must be securely tied to ensure their stability against wind impact (see fastening element 5 in Fig. 82). Such binding can be performed, for example, using wire, tape,)

Roof eaves: joints and installation

And 83. Roof eave (covering, thermal insulation, and waterproofing):

• 1 — eave board serving as a covering;
• 2 — drainage board;
• 3 — moisture-resistant plywood plate;
• 4 — roofing iron;
• 5 — elastic tape of bolts and other materials with anti-corrosion coating.

Then, it is necessary to secure the facing boards and sheets, equip gutters made of roofing iron if necessary, and perform thorough waterproofing to prevent leaks (special attention should be paid to the connection points of the structure). If necessary, it is recommended to use elastic adhesive tape in places that will be completely inaccessible after the installation of the roof and windows.

In cases where pressure-treated timber is not used, anti-rot protection should be provided for all surfaces, including sawn surfaces, at the connection points of the structures. However, sawn surfaces must be treated appropriately before the wooden structures are joined together.

Light-transmitting parts in structures. Before performing glazing and installation of glazed structures, it is advisable to paint the frame, as painting at later stages involves great difficulties. In this case, all metal parts of the structures should be thoroughly cleaned and painted with corrosion-resistant paint, even if they have galvanic coatings or have been hot-dip galvanized (many fasteners remain inside the structure).

Light-transmitting materials and facade systems

Light-transmitting materials. In addition to traditional clear transparent glass, numerous varieties of transparent plastics can also be used as light-transmitting materials, from which single- or multi-layer covering structures are manufactured.

When constructing a greenhouse integrated into a residential building, durable rigid or semi-rigid building materials are used. The characteristics of these materials are shown in Table 6.1. The authors consider the most important of these to be solar radiation permeability, weather resistance, suitability for installation and maintenance, as well as an affordable price.

The Finnish market offers multi-layer and cellular products made from the above-mentioned light-transmitting materials, and the thermal insulation and strength properties of such products are significantly higher than those of single-layer coverings, although their cost is also much higher. Table 6.2 provides data on the comparative cost of various materials.

Light-transmitting parts of the facade wall. Option 1. The simplest and most economical, but not always the most attractive solution, is the installation of light-transmitting sheets or elements directly into a wooden frame.