Forest House: reintegrating greenery in a high-density metropolitan area

We present “Forest House: reintegrating greenery in a high-density metropolitan area”, by Shma Company Limited.

Rapid urbanization results in high urban density. Green areas are sacrificed to meet the demand for residential areas. The lost green space significantly impacts the environment in many ways, importantly, air pollution.

This year, the PM 2.5 concentration level in Bangkok has risen up significantly high that it has visible effects on people’s health. Research says trees have the ability to trap particulate matter and produce oxygen, hence a way to tackle the problem.

Grow house.
Ilustration: Shma Comany Limited

It is time for us to rethink how to reintegrate green spaces back into the city. Bring back the healthy city, bring back healthy lives. The project is a research project aiming to find a sustainable and low maintenance way to bring back greenery into a private house, while still maximizing plot area.

With thoughtful and effective design, the lush green roof of the Forest House has been thrived beautifully, reintegrating trees into the city again. The Forest House project reflects the trend of urbanization. A new bigger home is built to replace the previous smaller one in the same plot area to cater for an extended family.

Exterior of the third floor.
Photography: Jinnawat Borihankijanan.

To integrate greenery as much as possible into the site area, the roof surfaces are utilized as planting spaces. With a careful design, the limited site area can accommodate more than 100 trees.

According to researchers, a tree can produce enough oxygen for 2 people, trees in the project then provide enough oxygen for 200 people. The amount of oxygen produced even exceeds the needs of the 7-people family, and generously spreads this oxygen to the surrounding neighborhood.

The following strategies are considered in the design process to ensure ideal planting location and method tree growth, with the least maintenance requirement.

Oxygen diagram.
Ilustration: Shma Company Limited.

1. Make room for trees
To make the most of the rectangular plot of 12 x 24 meters, the layout of the house is segmented into 3 sections with 2 courtyards in between. In addition to enhancing good wind flow to every room in the house, the layout also provides courtyard spaces for planting.

On the 2nd floor, a planter is integrated at the front of the house to provide privacy for the bedroom that faces the local street. Another planter is added in the courtyard to connect green space to the bedroom.

On the 3rd floor, where the roof is, the planter of 1 meter high, doubles up as a railing, occupying around half of the total area, leaving a flat surface for other functional use such as dining table, urban farm, and cloth drying area. Overall, trees grow on every floor from ground up to the roof.

Photography: Prapan Napawongdee

2. Forest in boxes
Average planter size is 1-1.5 meters deep and 2 x 4 square meters. Only 1-2 years old trees with trunk diameter of 1 inch are selected because the young root system has a higher chance to adapt to the limited soil condition.

The whole planter box is filled with high nutrient topsoil that provides food for the tree. To maximize the number of trees planted in the small planter, only columnar shaped trees are selected.

Indigenous tree species typically found in mixed deciduous forest are chosen as they demand less watering, hence saving the resource. More than 20 species of evergreen, flowering, fruit barring, and edible trees creates rich biodiversity for the urban area.

The design process allows trees to thrive through years rather than creating an instant thick forest which might not last long. Within 10 months after the completion, trees are grown up twice the height of the original size.

Photography: Jinnawat Borihankijanan

3. Urban farm
Roof surface is an ideal space for urban farms as it exposes plenty of sunshine required for herbs and vegetables. Another important function of the forest roof therefore is to produce fresh organic food for the family.

Thai fruit trees such as star apple, rose apple, and star gooseberry are randomly mixed with other forest trees to avoid attack from insects. Variety of Thai traditional herbs are planted in a series of 400 mm. deep planters.

Photography: Jinnawat Borihankijanan

4. Sustainable forest
As a private house, simple maintenance is planned to ensure the forest’s growth in the long run with no need of excessive resources. However, following topics are concerned in order to execute the sustainable forest:

Water irrigation: Slow release drip irrigation at tree roots saves the water used for plant watering. Perforated tubes running through the topsoil layer releases minimum water throughout the day and maintains sufficient humidity at the root of each tree. The system causes less excess water than the sprinkler system.

Natural composting process: Underneath the trees, no shrub or groundcover is planted leaving bare soil to be covered by fallen leaves. Dry leaves are not thrown away, but collected to fill the forest floor. Through time, the natural degradation process caused by microorganisms turns the leaves into natural nutrient-rich fertilizer. Each tree species consumes and produces different kinds of nutrients; therefore, a variety of trees are selected to balance the nutrient distribution.

As each tree grows at a different speed, branches of the faster growing ones can interfere with the growth rate of the slower growing ones. Therefore, pruning is required quarterly to provide enough space for the slower trees to fully grow.

Photography: Napon Jaturapuchapornpong

Species list

  • Fragrant flowering trees: Fagraea fragrans, Michelia champaca, Calophyllum inophyllum, Millingtonia hortensis, Shorea roxburghii G.Don, Citharexylum spinosum, Melodorum fruticosum.
  • Fruit bearing trees: Star fruit, star gooseberry, jackfruit, rose apple.
  • Distinctive flowering trees: Mayodendron igneum, Jacaranda obtusifolia, Spathodea campanulata, Lagerstroemia floribunda, Lagerstroemia speciosa, Lagerstroemia floribunda, Cassia grandis, Cassia ‘Siam White’, Shorea robusta, Gardenia sootepensis Hutch.
  • Evergreen trees: Azadirachta indica, Dalbergia cochinchinensis, Elaeocarpus hainanensis, Lagerstroemia speciosa, Dolichandrone serrulata (DC.) Seem, Swietenia macrophylla.
  • Thai herbs and vegetables: Basil, sweet basil, hairy basil, stevia grass, peppermint, spearmint, lemon grass, lime, chilli padi, butterfly pea, passion fruit, cucumber, climbing wattle, yellow-berried nightshade, mulberry.

Thai herbs and vegetables.
Photography: Prapan Napawongdee

Forest House project executes the idea of integrating sustainable greenery into dense urban areas without having to sacrifice build-up area. If the idea is applied throughout a city, a possibility to solve a persistent problem of the modern world such as air pollution will be open up.

It is time for us to rethink how to bring green spaces back into the city. Bring back the healthy city, bring back healthy lives

“The project is a research project aiming to find a sustainable and low maintenance way to bring back greenery into a private house.”

Photography: Shma Company Limited