FAQ’s

Liquid Rubber FAQ’s

Q.        How do Liquid Rubber Waterproofing systems differ from other types of
protective coatings?

A.        Liquid Rubber membranes are totally seamless, fully bonded, non-hazardous, cold applied, highly elastic and compatible with all types of roof construction.

Q.        Why is this important?

A.        Water ingress issues in flat and low pitch roofs tend to follow the same pattern dependant on the nature of design, manufacture and building use. In all climates variance in
temperatures cause structures to expand and contract causing stress on weak areas of the
structure and waterproofing membrane.  In addition to this thermal cycling other external factors can also affect the performance of the waterproofing membrane.   The majority of waterproofing membranes, irrespective of the method of sealing, create joints and seams which may succumb to splitting, cracks and perished seams allowing water to penetrate the building envelope.
Liquid Rubber forms a totally seamless membrane even when formed around complicated
shapes and services. This coupled with an elasticity of up to 1100% and 90 per cent
memory (recovery) eliminates the problems caused by thermal cycling and most other
external factors.

Q.        When a Liquid Rubber waterproofing system is used what can I expect
before, during and afterwards?

A.        Before, our technical help team is available Mon.-Fri. from 8:00am to 4:30pm to provide full technical support and a specification tailored to your specific requirements. This will also include advice on preparation of the substrate, application, handling, storage and
availability.   During the application of Liquid Rubber the building is usually able to continue with its’ normal day to day operations. With LRS very rarely is full removal of the previous
waterproofing system required or recommended. This reduces costs considerably, avoids
the risk of ingress of water and falling debris during the removal process and waste
materials being added to the landfill.  No flames are used or noxious fumes emitted during the application which reduces risk to buildings, plant, materials and personnel.
After completion the building will be secure from water ingress with a fully bonded, simple
to maintain, seamless membrane capable of moving with the building during thermal
cycling. These points coupled with our dedicated after sales service means peace of mind
for the building owner and user for many years to come.

Q.        Can Liquid Rubber be applied to any surface?

A.        Liquid rubber can be applied to most substrates, including concrete, asphalt, built-up felt, single ply, GRP, fibre cement, timber, insulation board and many more. When applying
onto semi-porous surfaces we recommend applying a sealing layer of ‘Liquid Rubber Flood
Coat’.

Q.        Does the surface need to be dry before application?

A.        Yes, the surface may be visually damp but there must be no surface water present.

Q.        Are there any limitations of application?

A.        Liquid Rubber has been used in wide range of applications across the globe. Its’ potential use extends beyond simple roof waterproofing membranes. The cured membrane can cope with extremes of weather and temperature. Liquid rubber should be applied at temperatures above 4 deg. C.

Q.        Can Liquid Rubber cope with ponding water?

A.        In accordance with good roofing practice areas of standing water should be avoided.
Standing water is not detrimental to Liquid Rubber membranes when cured. Consult our
technical help desk for further advice.

Q.        How fast can Liquid Rubber be applied.

A.        Liquid Rubber is very quick to apply; ‘Liquid Rubber Instant Set Spray Grade’ can be
applied at up to 1,000 Sq. Mt. per day.

Q.        Can I apply Liquid Rubber myself?

A.        Yes. ‘Liquid Rubber High Build’ is a two coat system which can be applied using a brush, roller or airless spray. Our Technical Help Team will be happy to advise on preparation and application of our products.   ‘Liquid Rubber Instant Set Spray Grade’ is a single coat specialist application normally applied on larger contracts. Contact our technical help desk for further information and advice.

Q.        Is Liquid Rubber safe to handle?

A.        Yes! Liquid rubber is non-hazardous, non-toxic, contains no solvents or VOCs and is
harmless to aquatic life. Liquid rubber does not require any special handling; consult our
COSHH sheets for full details.

Q.        How long does Liquid Rubber take to cure?

A.        Curing times vary dependant on atmospheric conditions and temperatures. In normal dry conditions Liquid Rubber High Build will be surface cured after approximately. 4 hours but ideally should be left overnight before applying the second coat. Overall curing times will vary greatly depending on weather conditions.   ‘Liquid Rubber Instant Set Spray Grade’ is surface dry almost immediately and normally 95% cured within 24 hours.

Q.        Can I walk on the Liquid Rubber?

A.        When fully cured Liquid rubber will cope with normal light foot traffic for general
maintenance, building repair etc.   For walkways, balconies etc we recommend Dekseal
Consult our technical helpline on 01405 780444

Living Walls FAQ’s

What is a living and benefits of a wall?

 Q.        What is a living wall?

A.        a living wall is a vertical surface filled with living, growing plants.  Plant on the surface of buildings is nothing new and many are familiar with Ivy, Virginia Creeper etc.

 

Q.        What are the benefits of living walls?

A         i.          they conserve energy by insulating the building envelope, reducing the need for heating in the winter and cooling in the summer.

ii.         they create wildlife habitats and provide biodiversity conservation opportunities

iii.        they absorb and filter storm water, which reduces local water body pollution and helps prevent the overwhelming of land water infrastructure.

iv.        they filter air particulates, improving air quality and help to reduce the urban heat effect

v.         the plants clean the air and add humidity to the air when you have your central heating on in the winter.

vi.        improve water quality

vii.       increase the service life of the building.

viii.      improve the aesthetic environment

 

Q.        Why would I want a vertical garden on my property?

A.        scientific research has shown that plants promote good psychological health. Historically, humans were accustomed to live in the lush surroundings of jungles, forests, savannas etc.  Everywhere plants affect us subconsciously, and make us feel at home on earth.

 

Construction

Q.        How much will it weigh?
A.            The wall will vary greatly in weight, depending on the product chosen, the depth and the material components.

 

Q.        Can living walls be built indoors?

A.        Living walls can be built indoors and outdoors and depending on where the wall will be built, different factors will affect the construction, choice of plants and maintenance of the wall.

 

Q.        How would a living wall impact upon an indoor space?

A.        Living walls is that they increase humidity levels in an enclosed space and in cold climates where windows are kept closed for long period’s homes and offices become dry.   A living wall will make rooms more pleasant to spend extended periods of time in.

 

Q.        Is there a size limitation on living walls?

A.        There are no limits to the size of living walls.  With a modular system living walls have been built to staggering heights and long lengths…

 

Q.        Can a living wall survive through winters?

A.        The plants in living walls are no different from conventional, garden and some plants will lose their bright colours and turn dull, whilst others will lose leaves and regenerate in spring.   You can plant evergreen plants in wall for all year colour.   Indoor plants are beautiful all year round.

Some more exotic plants may need some form of protection during the course of the winter

 

Q.        Does a living .wall require much maintenance?

A.        Once installed, a living wall pretty much takes care of itself maintenance is kept to a minimum.   If, edible or medicinal plants then you will need and be able to harvest at regular intervals.   If you are growing fruit-bearing plants, such as tomatoes, you may need to arrange energy supply.

 

Q.        Can I see any examples of living walls?

A.        There are numerous examples all over the UK.  If you contact our sales office we will send you details.

 

Plants

Q.        What plants are used in living walls?
A.        This depends on location, climate, budget, exposure, availability, location etc.  Local native plants provide food for our local birds, insects, butterflies etc.

 

Q.        Can any plants grow on living walls?

A.        Not all plants are suitable for growing on living walls, because of their root systems or are not compatible with the conditions.  This still leaves long list of beautiful plants of all colours, shapes and sizes that work well in living walls.

 

Q.        Can food plants also grow on living walls?

A.        Food plants can grow on living walls, however, indoor living wall that includes food plants can be more expensive than one that does not.   The ability to grow your own fresh vegetables in the middle of winter could be attractive!

 

Q.           Can I grow vegetables in my living wall?
A.            Some people successfully grow lettuce, herbs, beets, radishes & carrots in their walls.

 

Q.        How can plants grow on a wall without any soil in it?

A.        Plants require water and nutrients and are able to grow well without soil, as long as there is a steady supply of water and nutrients.   If you consider the lush vegetation in tropical rainforests that climbs and clambers over soil-less rock and a living wall simulates these same growing conditions.

 

Q.        How are the walls watered?
A.        The system comes with a fully automatic irrigation system to allow every area of the wall the correct amount of water.
Q.        How much water do the walls need?
A.        The fully automatic irrigation system allows every area of the wall the correct amount of water.

 

Q         What happens to all of the water that runs down the wall?

A.        The irrigation system recycles water back to the top of the wall.  A small pond can be created at the base and can contain fish.  The excrement of the fish that dissolves into the water makes good food for the plants.

 

Lighting and Energy

 Q.        Will the lighting required to grow food indoors be too intense for people?

A.        Special grow lights can be installed in the frame to allow tropical plants and humans can comfortably cohabitate.

 

Q.        What kind of light do I need for my living wall?
A.        It preferable to erect the wall where it will receive some natural light.   Otherwise you can install artificial lighting if necessary, although it will be necessary to specify plants that survive low light.

 

Q.        How will an internal living wall affect my energy consumption levels?

A.        Without a living wall, new air must constantly be brought in from the outside to refresh the indoor environment.    This must be heated in the winter, and cooled in the summer, to achieve a comfortable room temperature.

 

Lifespan and sustainability

 Q.        Why are our living walls considered sustainable?

A.        Living wall panels are designed with computer controlled irrigation systems to suit the size and complexity of each scheme.

 

Q.        How long does a living wall last for?

A.        Various forms of living walls have existed for centuries.   After many years many modern projects continue to fulfil their function and their plants surviving and thriving.

 

Cost

Q.        How much does a living wall cost to install?

A.        The cost of installation depends on a number of factors, size, location, indoor or outdoor, type of plant etc.

 

Fire 

Q.        Is there a danger of the plants catching fire?

A.        If the wall is designed correctly there should be no danger for fire.

 

Q.        Can the living walls be installed on a sloped roof?
A.        Sloping walls can be designed.  Contact our office for details.

Green Roof FAQ’s

a. WHAT IS A GREEN ROOF?
A green or ‘living’ roof is essentially the growing of plants on our rooftops with vegetation layer covering a roof structure, with growing media and plants taking the place of bare membrane, gravel ballast, shingles or tiles. The insulation properties of soil and plants have been utilised by humans for thousands of years, cooling buildings in Africa and helping to retain heat in traditional buildings of Northern Europe and Scandinavia. Green roofs can be anything from a thin growing layer of sedums and mosses to plants, shrubs and water features. They are installed on top of conventional roofs and properly designed, they are stable, living ecosystems that replicate many of the processes found in nature.

b. TYPES OF GREEN ROOFS
Extensive are lightweight, less expensive and low maintenance. Normally less than 6 inches deep growing medium, and, depending on depth, may support a range of plants include Sedums (low-growing succulents), and other succulents, flowering herbs, and certain grasses and mosses such as herbs, meadow grasses, and perennials. . Suitable for use on slopes up to 30° pitch. Steeper ones can be installed with raised grids or laths to hold plants and growing media in place.

Intensive can be thought of as a garden on a roof with lots of shrubs, flowers even trees along with walkways and flowerbeds, is heavier and needs more support and is more expensive. Deeper growing medium can sustain complex landscapes, including small trees and even small ornamental ponds and fountains. Intensive roof greening usually requires irrigation and maintenance, as the roofs have plants of reasonable size for a traditional roof garden.

Bio-diverse or Brown a selection of local growing mediums, aggregates, recycled materials and timber, stones normally distributed around the roof surface. This is either left alone to allow the germination of wind-blown seeds, or alternatively, seeds collected from the local area are scattered over the roof area to achieve the biodiversity and recreate the surrounding wildlife habitats. Over time an ecosystem of plants and animals will develop on the roof similar to the local environment.

Buildings would need to be designed specifically for this type of system because of the strength requirements of the structure. Where a habitat is being designed to support a specific species, conservationists will normally be consulted to assist in devising a roof-top habitat that will attract and support the target species.

c. EFFECTS OF GREEN ROOFS
What are the major advantages of green roofs?
Green roofs provide many ecological and aesthetic benefits, including:
• Controlling water runoff, erosion and pollution,
• Improving water quality,
• Mitigating urban heat-island effects, cooling and cleaning the air,
• More than doubling the service life of the roof,
• Conserving energy,
• Reducing sound reflection and transmission,
• Creating wildlife habitat, and
• Improving the aesthetic environment in both work and home settings.

How does a green roof affect the conventional roof below it?
By covering 100% of the waterproofing materials protecting it from human activity, windblown debris, UV radiation and variations in temperature extremes this minimises damage daily expansion and contraction.

How do Green Roofs affect the building they are on?
By reducing the temperature inside the building on during increasingly hot summer months and thereby reducing costs associated cooling buildings and the need for air conditioning in the summer result in a reduction of CO2 emissions whilst keeping the building cool.

How do Green Roofs affect the quality of life for people?
Where accessible Green Roofs can be used for social and leisure activities and contribute to a greener urban environment and quality of life for communities, particularly in high density areas.

How do Green Roofs affect wildlife?
Because new developments often result in a loss of habitat and Green Roofs create green space in urban areas, they maintain species vital to local biodiversity. In particular they have been to attract many rare invertebrates found on brown field sites, as well as ground nesting birds such as skylarks.

What effect will the winter freeze and thaw cycles have on the roof?
Because not all green roofs are resistant to freeze and thaw cycles care should be taken in the selection of plants and design of the system.

Is there erosion in the winter when the vegetation dies back?
When designing a green roof system it should include a significant percentage of non-deciduous plants, so that the mature cover is never bare of foliage and the potential for erosion is reduced.

d. PLANT VARIETIES AND GROWING MEDIUM
Plants will vary by region, but generally, the deeper the green roof, the more complex the type of plants that can be sustained. Where frost occurs, half of the plants on an extensive green roof should be varieties of Sedum. In colder climates grass-dominated covers are recommended and tropical plant is not recommended, but other plants can be incorporated to provide habitat value or visual interest.

Are any green roof plants invasive non-natives that could be spread by wind?
Sedum sarmentosum also known as Star Sedum, Gold Moss, Stringy Stonecrop, or Graveyard Moss has green spearhead-shaped leaves, lemon yellow flowers, and long tendrils could be considered invasive and is not recommended.

What kind of soil is suitable? Can I just put top soil on my green roof?
Normal garden soil is heavy and contains undesirable insects and weeds and you do not know what’s in it. Growing mediums need to be lightweight, drain properly, but retain a certain amount of rain water.

Are green roofs necessarily green in colour?
Many green roofs appear red, orange, yellow and all colours in between at different times of the year because the fleshy leaves of various succulents change colours throughout the year. This can lead to anticipation with the variation flower colours from whites to yellow, pinks, deep reds and purples and blues creating a virtual living carpet or tapestry varies from season to season

Can green roofs be combined with other green features?
Green roofs can be designed in conjunction with solar panels and in combination with other ‘low-impact’ development measures, such as infiltration beds, rain gardens, bio-retention systems, cisterns and rain barrels.

How are green roof plants started?
There are several methods for starting green roof plantings. Perennials can be seeded or may be established from fresh cuttings or from plugs planted a foot apart.

Can I plant a vegetable garden on my roof?
Generally, green roof systems are not deep enough for growing vegetables and the tools of traditional gardening would damage the green roof and the underlying waterproofing. However, incorporating container gardens or modular elements can accommodate an owner’s desires.

Where can I buy seeds to plant my own green roof?
We can either supply plants or seed or advise you where to buy them.

What about pre-planted modules
Apart from planting seeds of plugs you can buy ready planted modules that are 500mm x 500mm x 50mm depth with water retaining cuplets, incorporating drainage holes. These overlap with adjoining modules by 100mm, and interlock into overlapping cuplets to provide an instant green roof finish.

How long until the green roof will be fully covered?
Generally, a green roof that is planted correctly will reach maturity in two growing seasons, or less. Depending on the level of sun or rain may slow the process. However, pre-grown Sedum mats, can be used for an instant garden finish.

Will ordinary grass or grass sods be suitable for a green roof.
Historically people used the materials close at hand for hundreds of years in many parts of the world. A monoculture of plant species is not considered healthy or desirable for roof garden system because it could be open to plant. disease or insect infestation. Ideally plant varieties should be ecologically diverse, with many types of vegetation to be vibrant and healthy. Grass or grass sod need to be watered, fertilized, and cut regularly, so they would incur greater costs for maintenance.

e. DESIGN AND CONSTRUCTION
What if my roof isn’t flat?
The term flat roof is a contradiction and it needs to allow water to flow off the surface and therefore should not be actually flat. Most green systems can be laid to a pitch of 40 degrees quite comfortably with the help of retention bars to prevent slippage while allowing excess water to drain through.
What are the most important factors in designing a green roof?
• Climate, especially temperature and rainfall patterns
• Strength of the supporting structure
• Size, slope, height, and direction of the roof
• Type of underlying waterproofing
• Drainage elements, such as drains, scuppers, and drainage conduits
• Accessibility and intended use
• Visibility, fit with architecture, and owner’s aesthetic preferences
• Fit with other ‘green’ systems, such as solar panels
• Costs of materials and labour

Are leaks under a conventional green roof a problem?
Leaks in the waterproofing layer are less likely when it is protected from the elements by a green roof. If a leak does occur, it can readily be located by using new and more reliable electronic technology which can quickly and accurately pinpoint problems. Repairs to the waterproofing are quick, and disturbance of the green roof is minimal.

Do green roofs cause leaks?
Only poor installation or incorrect specification of the waterproofing materials can result in leaks on green roofed buildings. When installing a green roof onto an existing building, care must be taken not to damage the existing roofing material and a ‘root-resistant’ element is installed.

Is attaching all elements of the green roof to the underlying structure important?
Plant roots bind the layers of media and fabrics to create a unified cover, and the plants themselves create enough surface wind turbulence to reduce potential wind uplift. If the green roof is to be located in an unusually high wind area, such as a high rise building or coastal area it may be appropriate to use ballast.

How steeply pitched can the roof be?
The maximum slope recommended for conventional green roofs is 30 degrees, pitch. If roofs have a pitch greater than 30 degrees, special techniques are required.

What kind of waterproofing do I need?
Many types of waterproofing are compatible with green roofs. Mastic Asphalt, bituminous membranes, single ply and liquid coatings are the most common. With the exception of Mastic Asphalt, which because it’s close texture will not permit penetration it is necessary to have the final layer which is root-resistant for all types of green roofs to avoid the risk of roots penetrating the waterproofing.

What guarantees do manufacturers offer?
Waterproofing manufacturers offer varying lengths of guarantees dependant on products and systems and when it is installed by an approved contractor. There are some guarantees for the green roof’s plant element.

How do green roofs affect the life span of a roof?
The lifespan of standard roofing material in good condition is at least doubled by the addition of a green roof by protecting the membrane from corrosive UV rays and temperature fluctuations which occur throughout the day.

In what climates do green roofs work?
Green roofs have been built most widely in temperate climates, but special techniques allow them to thrive in semi-arid, tropical, and even windy coastal areas and have been installed from hot, moist to the cold, windy locations.

Can recycled materials be used in constructing green roofs?
Recycled materials can be used and there use should be considered in the design to reduce the use of virgin materials. Recycled materials are particularly suitable in Bio-diverse or Brown systems.

Is my roof strong enough to support a green roof?
Green roofs vary greatly in weight, depending on their depth and the materials used. The important measurement is ‘wet’ weight which could be about 60-150kg square metre. Calculation should take into account the weight of water held in the soil and any snow loading.

Does a green roof weigh more than traditional roof?
A green roof weighs more than a conventional roof due to the weight of substrate, vegetation and their water and can be easily factored into the structural design of a new development. Existing buildings can be retrofitted with a green roof, but may need to be reinforced to take the additional weight.

Do I need to consult a Structural Engineer?
It is always advisable to contact a Structural Engineer or discussed the design with Building Control to ensure they are satisfied that the nature of the work.

Does a Green Roof require planning permission?
It is always advisable to check with the local planning department who will advise you on what steps should be taken.

Can a green roof help me get planning permission?
Green roofs improve the aesthetics of a building, especially when the plants flower, with small blooms of yellow, pink, white and red flowers at different times of the year. These aesthetic qualities may help when applying for planning permission for new buildings because it actively removes pollutants from new site whilst disguising or hiding new development.

Do I need building regulations approval?
When replacing an existing roof with a green system you will not normally need building regulation approval with the exception meeting new thermal regulations. If it is a new roof you will need approval.

f. FIRE
Are green roofs a fire risk? Is there a danger of dry plants catching and spreading fire? By choosing plants that store water in their stems and are inherently non-flammable, coupled with gravel borders and breaks protect against fire to create a better fire rating than conventional roofs if designed correctly.

g. COSTS AND FINANCIAL IMPLICATIONS
How much does a green roof cost?
Cost depends on many factors: the size and slope of the roof, depth and complexity of the system, height and accessibility from the ground, cost of labour, and need for specialised elements, such as drains, railings, pavers, slope stabilization measures, etc.

Is there any funding available to install a green roof?
There is currently no governmental funding or incentives available specifically for green roof installation in the UK. However, it is sometimes possible to win funding for outcomes such as habitat replacement/introduction or urban agriculture, and then apply it to a roof space.

What financial benefits do green roofs provide?
Because years of experience throughout the world have shown that a green roof can be expected to outlast a comparable ‘normal’ roof by a factor of at least two, and often three, this goes a long-way toward paying back the initial investment in a green roof.

Will a green roof reduce energy costs?
Acting as a heat sink, slowly absorbing and holding energy from sunlight and releasing it when the ambient air cools, this acts as a heat “storage battery” and reduces the heating and cooling demands within the building.

h. INSULATION AND ‘U’ VALUES
What is the typical U-Value of a green roof?
No specific thermal value is given to the green roof itself but current regulations must be achieved by using the correct insulation within the roof construction itself. The roof will however benefit from increased protection from heat in the summer and some protection from cold in the winter. We can provide you with the appropriate calculations to meet the requirements.

Sound insulation
Green roofs help reduce noise and are good in high noise areas such as near airports or where noise reduction is required for example hospitals, respite homes etc.

i. MAINTENANCE
Who should maintain my roof?
Whilst should be minimal for most green roofs, homeowners should check a flat or low pitch green roof if access is good and does not present a danger. Where the project is too large or an intensive roof system installed then a roofing professional should be recruited to provide a maintenance service of at least twice per year.

What kind of maintenance is required and is an extensive green roof really maintenance-free?
Regard how drought tolerant plants Green roofs should be monitored and checked periodically for invasive weeds, disease, etc and to occasionally infill of plants. Maintenance visits should be timed to intercept any weeds before they go to seed to maintain the health of the plants and protect the underlying roofing materials.

Will I be able to walk on my green roof? Can it be used for recreation?
Where the roof is accessible from the building and it will support the weight decks, patios, and walkway pavers can be integrated into the design of the green roof. Care must be taken with the selection of plants and only turf grass will stand up to regular foot traffic. Alternatively, if more fragile plants are installed then stepping stones or walkways can be used to provide access through green roofs.

Is access to the roof needed?
Every green roof requires some degree of maintenance to ensure it is kept in top condition, so providing provision for access at an early stage is always beneficial. Health and Safety regulations require anyone within 2m of a roof edge to wear a safety harness. Brackets, man safe systems, edging or fall nets can all provide attachment points and protection from falls.

Do I have to mow my green roof?
Sedum systems never grow beyond a few centimetres in height and never need mowing. If you choose a grass or wildflower systems, when strimming is recommended at the end of the growing season once the seeds have self-sown.

Do I have to water my green roof?
Extensive If you have chosen the correct drought tolerant plants the there should be no need to water except in extreme periods of drought other than the first year of whilst plant system becomes established. For large projects some form of drip irrigations which is inexpensive and delivers the correct amount of water to the base of the plants will be ideal.

Intensive Because an intensive green roof can be a combination of a large variety of plants, shrubs and trees and their watering requirements will be much higher than succulents and herbs. It should be treated like any ground level garden or landscape and watering should take into account the drying effect of high winds. Usually large intensive green roof projects have an irrigation system installed that can be environmentally friendly using a traditional active irrigation system or a solar powered system and recycled rainwater collection system and you’ve got the ideal self-sustainable supplemental water system.

Bio-diverse or Brown the basis of this type of green roof is to allow nature to take over naturally.

Is irrigation required? If so, what kind?
With thoughtful planning irrigation is rarely necessary. When irrigation is required, the water should be delivered deep under the surface—where the roots will seek it and it will not be lost to evaporation. Surface irrigation systems are wasteful and require more maintenance than subsurface irrigation methods.

How do Green Roofs affect water drainage from the roof?
Research indicates that Green Roofs reduce annual run-off roofs by at least 50% contributing to urban drainage and flood alleviation schemes. The rate of release following heavy rainfall is slowed, reducing the problems associated with storm surges.

Should I fertilize my extensive green roof?
There is some argument about whether this is necessary to fertilise a green roof. It is probably preferable to use encapsulated slow release fertiliser during the first year of establishment in spring and autumn. After that the natural cycle should take over and enough organic material should have composted itself back into the soil substrate to provide sufficient nutrients to the plants