Anything that is kept outside 24/7 all year round will be susceptible to mould and algae growth. Especially if the product is kept outside and will absorb water. Water absorption occurs in most products with natural components.
However, mould is an easy growth to remove and potentially prevent. If mould is left untreated, it can cause issues for your Decking such as rot and decay, which could lead to potentially dangerous structural problems.
This article will discuss what causes mould growth and how it is best to prevent it.
About Mold on Decking
WHAT CAUSES MOLD & MILDEW ON DECKS?
Just like Timber or wood Decking, Uncapped Decking Boards are susceptible to Mold and Mildew. Mould and mildew are classed as fungi, a type of plant without any leaves, flowers, or stems. These natural spores grow when the conditions are right.
Warm, moist air partnered with warm water is the optimal condition for them. Mould will only start to grow on a surface when it has been wet for over 24 hours, a regular occurrence in the UK.
Mould on Composite Decking is not uncommon. However, it should only occur on uncapped Boards, which do not have any additional protection ensuring the Boards interior is sealed to the elements. Capped Composite Decking Boards should have a reduced risk of mould, thanks to the added layers of protection added to the Boards, which protect the natural wood elements of the Boards.
HOW DOES MOLD GROW ON DECKING?
A Deck Board is a fantastic food source for mould. If met with the optimal conditions, aka warm and moist, then mould will grow on your Deck.
As with anything that is kept outside, exposed to the elements, and in a damp environment, mould will grow. A composite deck surface that is not properly protected, aka if it is not capped, and submerged for an amount of time in the water, will mould growths.
Mould growth on decking, composite (uncapped), or Timber when the conditions mentioned above are met. Mould will not only grow on your Decking but will eat away at it, mold will often lead to more extensive and expensive damage such as rot and stability issues.
Mold Resistance By Deck Type (Composite or Wood)
Mould occurs naturally in the wild, so most Deck Boards are susceptible to a degree. However, certain Deck types are going to be more vulnerable to Mold and Mildew than others.
Untreated, treated, hardwood and softwood timber Decking Boards will be more at risk of having fungi spores crop up compared to Composite, PVC or Aluminium Decking Boards. Timber Decking Boards have an all-natural core and the wood fibres are the perfect food for mould.
Untreated Decking - Least Resistant - This style of Deck Board is the most susceptible to mould growth. The wood fibres within the Deck surface have no protection from absorbing any additional water or mildew, or mould growth.
Pressure Treated Wood Decking - Less Resistant - While treated timber decking boards have slight protection against mould growth, mould and mildew can still grow if the conditions are correct. Natural wood fibres are the ideal food for fungi.
Uncapped Composite Decking - Resistant - While Composite Decking Boards have low absorption rates and a reduced amount of natural materials. Uncapped Boards are left unprotected. Therefore moisture can penetrate the Boards and mould can grow.
Capped Composite Decking - Medium Resistance - Capped Composite Decking Boards have a low absorption rate and a reduced amount of natural fibres within the Boards' core. Capped Composite Boards have an extra layer of protection which helps to prevent moisture from penetrating the Boards, reducing the risk of mould growth.
PVC Decking Boards - High Resistance - Cladco PVC Decking Boards are created with a PVC core encased in an industrial standard ASA Resin for increased protection. Thanks to the lack of wood material within the Board, PVC Decking has a low absorption rate, reducing the amount of moisture settling in the Boards and encouraging Mould growth.
Cleaning & Removing Mold & Mildew From Decking
HOW TO REMOVE MOLD FROM COMPOSITE DECKING
It is always recommended to check with your Decking supplier on how best to remove mould from the Boards as some materials used in Boards should not have certain chemicals or cleaning solutions used on them. When mould spots appear on your beautifully laid Deck, it can be frustrating and gives the Deck a dirty, run-down appearance.
In most cases Composite Decking, thanks to their low-maintenance properties. Removing mould, by cleaning the root problem away can be done quickly and effectively, using either Composite Deck Cleaner or kitchen dish soap and warm water to Clean Composite Decking.
Step 1 - Remove any furniture lighting and pots from your Decking. Then, with a brush (can be a stiff or soft bristle brush), sweep away any debris and dirt.
Step 2 - If not using Decking Cleaner - Prepare a bucket of warm soapy water. To that, add a small amount of light dishwasher detergent.
Step 3 - Cover your Deck with a light coating of the Deck Cleaner or Soap Water, and once applied, use your Hard bristle Brush to gently scrub the Deck. This should start to remove any surface stains or dirt. Scrub the entity of the Deck thoroughly to remove dirt, stains, and mould.
Step 4 - Leave the Soap water or Deck Cleaner to sit on the Deck, allowing the cleaning properties to soak into the Deck, removing any stubborn dirt or stains.
Step 5 - Rinse the solution away thoroughly, and leave it to dry naturally. Once dry, replace all your garden furniture and pot plants.
Step 6- Repeat steps 1-5 as often as required for the staining to minimise.
Can you pressure wash Composite Decking?
Using a pressure washer is not recommended with Composite Decking. If your Deck has a mould issue, Pressure washing it can sometimes cause the problem to worsen. Composite Decking Boards are often softer than traditional timber decking, and subsequently, the Boards could be damaged or marked if a pressure washer is used on them.
However, if the pressure washer is used on Composite Decking, ensure the pressure is lower to help minimise any damage and keep the end of the hose 12 inches away from the deck's surface.
Cladco Recommend Cladco Owatrol Composite Decking Cleaner to clean your outdoor living area and to help minimise dirt, stain, and mould build-up.
HOW TO REMOVE MOLD FROM WOOD DECKING
Removing mould from a wooded deck is an ongoing process. Timber Decking requires regular maintenance, compared to Composite Decking. Including regular varnishing, staining, sanding, and painting. Compared to Composite Decking, which does not require regular maintenance. Regular Deck Cleaning and maintenance are recommended to help keep your Deck clean of debris, mould, and mildew.
You should not use a Chlorine Bleach solution on your Timber Decking Boards as this can further damage the Boards.
Step 1 - Remove any furniture, lighting and pots from your Decking. Then, with a brush (can be a stiff or soft bristle brush) sweep away any debris and dirt. This will make cleaning the Deck easier, and any grease, dirt, and stains will be easier to clean off.
Step 2 - Before covering the deck's surface in cleaning solution, spray the Decking with water to loosen any further dirt and debris from the Boards. This is an easier way to clean the Boards.
Step 3 - Mix your cleaning solution together, with warm water mixed with an oxygen bleach solution. Or if you are using your chosen timber decking cleaner, follow the instructions on the cleaning material. Soapy Water can also be used to clean your Deck.
Step 4 - Cover your Deck with a light coating of the Deck Cleaner, Bleach solution or Soapy Water, and once applied use your Hard bristle Brush to gently scrub the Deck. This should start cleaning away any stains or dirt on the Deck materials. Scrub the entity of the Deck thoroughly to remove dirt, stains and mould. Some areas of your Deck may demand further cleaning and then others.
Step 5 - Leave the Soapy water, the mix of bleach solution, or the Deck Cleaner to sit on the Deck, allowing the cleaning properties to soak into the Deck, removing any stubborn dirt or stains. Before giving the Deck a rinse.
Step 6 - Rinse the solution away thoroughly, ensuring no bleach is left on the Deck, and leave it to dry naturally. Once dry, replace all your garden furniture and pot plants. Ensure the Deck is completely free of any cleaning solution.
Step 7- Repeat steps 1-6 as often as required for the staining to minimise.
Can you pressure wash wood decking?
Often a pressure washer can effectively clean a Wooden Deck. The hose can hone in on certain stains and dirt and wash the stains, mould, and dirt with ease. However, if the power washer hose is not used correctly, the spray can damage the surface of your deck materials. If the pressure on your hose is too high, it can cause discolouration across the Deck Boards.
There are many Decking Cleaning products on the market today, ranging in price, properties, and quality. It is recommended to go with a cleaner product that your decking supplier suggests for you.
HOW TO PREVENT MOLD ON DECKING
As with anything that lives outdoors, your Deck is going to be at risk of growing mould. A Composite Deck has a lower mould growth risk compared to Timber Decking. Any exposed natural elements of your Decking increased the risk of mould growth. So a Capped Composite Deck or PVC Deck with little to no natural elements will have the highest resistance to mould.
Deck Cleaning and a regular spray of a mix of cleaning solution and warm water can help keep your Deck free from dirt. However, mould will grow on an area of your Deck which is kept warm and moist with a food source for the fungi.
The best way to prevent mould growth on your outdoor deck is to keep the Composites, Timber, or PVC Decks as clean as possible.
Regular Deck Cleaning can help with mould issues and help increase the look and lifespan of your Composite or Timber Decking.
Clean, mould-free, Decking areas are a wonderful addition to any property, creating an area for outdoor dining, socialising, and relaxing.
Ensure your Deck is kept clean with regular cleaning, rinsing, and maintenance, for a long-lasting Composite Deck free from mould issues.
If you are interested in purchasing Cladco Composite Decking or PVC Decking for your property, the easy-to-use Cladco Calculator can be used to estimate how many Boards, Trims, and Fixings you may require.
Or, sample the range of Decking Boards available here.