What to do if your Basement is Flooding

Many properties across the UK have basements and cellars that are subject to flooding and moisture leaks, especially during periods of bad weather or because of a high water table. This is because basements and cellars are below the ground, meaning moisture can penetrate through walls, floors and even into the space from above.

There are steps you can take to mitigate the problem, but the best method is to carry out basement waterproofing, which will create a dry and habitable living space. This can be a valuable investment for homes and businesses, preventing the risk of flooding and leaks long term.

Typically basements and cellars will flood either because moisture has penetrated through the walls or floors, or because ground water or flood water has come in from above. Either way unwanted flooding will lead to damaged stored goods, furnishings and can even cause structural damage to timber through problems such as fungal decay.

Your property could be more likely to flood if you are in an area with a high water table, or you live in an area prone to flooding. Sometimes basements have existing drainage systems, but flood water can cause these to become blocked with debris or cause charged systems allowing water to ingress through the drains themselves. Even guttering and downpipes leading to soakaways can cause water to penetrate into the basement walls. You should take time to fully investigate this externally to make sure this isn’t the source of the problem.

A common cause of leaks and flooding is from hydrostatic pressure. This is caused when soil becomes saturated from burst water mains, rain or a high water table and the force exerted by groundwater on basement walls and floors causes moisture ingress. Moisture will penetrate through porous masonry walls and floors.

Over periods of severe rainfall soil will become saturated, which leads to an increase in the water pressure on walls. This will lead to further moisture penetration through tiny cracks, and over time can lead to structural issues like bowed walls and larger cracking.

Improvements to drainage can help alleviate pressure on below ground surfaces, but ultimately to guarantee a dry space you will require a waterproofing system designed to handle moisture ingress. We always also recommend that any drains serving the below ground space are protected with anti flood valves to prevent ingress from charged sewer systems which could also flood the below ground space.

If you have a flooded basement, the first step is to ensure the electricity and gas are turned off, and then taking steps to remove all standing water. Damaged items will need to be removed, and all surfaces will need to be decontaminated. Flood water can contain a variety of harmful substances like sewage, chemicals, and other debris.

You will then need to dry out the internal space to prevent damp related issues such as mould and structural problems like fungal decay. Damaged fixings like plasterboard and drywall will also need to be replaced.

Flood damage can cause significant damage to stored items, furniture and other goods in a basement and cellar, which may be unsalvageable and will need to be disposed of. It can also cause noticeable structural damage which will need to be dealt with. If these problems are left it can lead to an unhealthy environment and even more costly repairs in the future.

If you are unsure on the best course of action, a CSSW qualified professional will be able to carry out a basement survey, and provide you with advice and solutions.

The best way to prevent future flooding and create habitable living areas in your basement or cellar is to install a basement waterproofing system to BS8102 standard.

The British Standard 8102:2022 ‘Protection of Below Ground Structures Against Water Ingress’ is a code of practice which provides recommendations and guidance for waterproofing below ground spaces. British Standard 8102:2022 states that all below ground systems should recognise all external sources of moisture, including surface water, flood water and groundwater. This means for a dry and habitable living space recommendations must be followed to ensure a robust waterproofing system is designed and installed.

A CSSW qualified surveyor from Peter Cox will be able to carry out a waterproofing survey of your property, and provide a report with their findings. This will detail recommendations for a waterproofing system designed specifically for the property involved, taking into account high ground levels and flooding risks.

If you choose to go ahead with the basement waterproofing system, Peter Cox technicians will be on hand to help. Peter Cox are approved installers of Delta, Koster, Newton and Safeguard waterproofing products, and all of our technicians undergo rigorous in-house and onsite training in order to be able to qualify as a trusted partner.

We are rated ‘Excellent’ with over 2,500 independent reviews on Trustpilot and are a Which? Trusted Trader, CHAS and Safecontractor approved and are registered as a Quality Assured Firm under ISO 9001.

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  What are the dangers of a flooded basement?

  Flood water in basements and cellars can cause bacteria, sewage, chemicals, and other debris to enter your property. Standing water will cause damage to plasterwork, flooring and other furnishings. If timber is left saturated it can lead to fungal decay. Mould growth may occur on cold damp walls.

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  Is it normal to have water in the basement after heavy rain?

  No, basements are meant to be dry if they are used as storage or a habitable space. If heavy rain causes your basement to flood you may need waterproofing to prevent it happening again. Water can penetrate through cracks and porous masonry, and overflowing drains can exacerbate the issue. It can even rise up through a 'solid' floor. Waterproofing can prevent issues like damp, mould growth and fungal decay.

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  What happens if you don't clean a flooded basement?

  If you do not clean away and remove flood water, you risk structural timber becoming rotten. Wet rot and dry rot spores germinate on timber when there is a source of moisture, and can lead to significant structural damage. Dry rot can spread through a property in search of more timber to attack.

  Standing water can lead to increased humidity in a basement, which in turn can cause mould growth to form on damp and cold walls and surfaces.

  Electrical items and other furnishings may become damaged when stored in a flooded basement.

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  Can you fix a basement that floods?

  To fix a basement that floods you may require a basement waterproofing system, which is designed to provide a dry and habitable space. When designed to BS8102 guidelines a basement will be completely dry internally, creating extra space and can add value to your property. In many areas basement waterproofing can be a valuable investment.

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  How long does it take for a flooded basement to dry out?

  This will depend on the severity of the flooding, and the steps taken to remove excess moisture. Standing water can be removed by increasing drainage to the basement, but masonry walls and floors may take weeks or months to fully dry out, if at all. For a fully dry basement you may require basement waterproofing which can deal with high levels of moisture ingress.