Flood Protection Advice
Industry standard flood protection height is 0.60m, however, it is possible to defend properties up to 0.90m above threshold level by the use of resistance measures such as flood barriers, flood resistant doors etc... Defending a property above this level could affect the structural integrity of the house. No attempt to increase the level (height) of protection above this limit should be undertaken. Based upon the information collected about the property, flood protection measures would be recommended to help reduce flood risk to the property. These measures are the minimum that are required to help reduce flood risk. All measures would have to be carried out to help reduce flood risk to the property.
When recommending products we consider the type of construction, age of the property and local circumstances etc and other factors that would offer the best solutions for flood protection.
It is possible to defend most properties up 0.90m above threshold level by the use of resistance measures as outlined below.
Grants
Sometimes there are grants available from the council if you suffer from flooding, we would recommend that you contact your local council and water authority to see if there is any help available.
General advice:
Unfortunately, it is impossible to guarantee that you will never get flood water into your property, it is nature’s most devastating force and will always find a way in. Having said this, there are a wide range of products available on the market, all of which have been tested and proven effective when installed and used correctly. Due to the immense pressure the water will put on the fabrics of the building, the property may be at risk of structural damage. We therefore recommend that any water that is above 600mmm deep (from your floor level), you allow the property to flood. If you are wanting to protect above this level you will need to get advice from a structural surveyor.
Your home / business is probably the most expensive thing you will purchase and so deserves to be looked after. By investing wisely in adding flood resilient products, it will have lasting effects. Not only will they help you to protect your property, they may also help with insurance and when you come to sell the property as it will stop potential buyers trying to reduce the value of it.
The 2 types of flood protection:
Reactive protection: Products such as barriers and covers etc that need to be manually installed.
Passive protection: Products such as doors and automatic air bricks ensuring round the clock protection.
The 4 main ways to mitigate your property against flood damage:
1. Boundary protection: Potentially, this is the best way to protect your home as it stops the water before it even gets to your door. However, depending on the structure of your property, this may not always be possible and the most appropriate option for you.
2. Aperture protection: This prevents water coming in through openings in the structure, e.g. doors; air bricks; pipes; cable entry; gas/electric boxes; drains.
3. Seepage: Through walls and floors of your property, this is almost impossible to stop.
4. Removal: Removing any water that gets in and keeping damage to a minimum.
1. Boundary protection: The perimeter of the property will need a wall, fence or barrier that has a strong enough structure to protect the property against rising water. All apertures will need to be blocked as well such as gate opening. This can be done by using removable barriers or hardwood flood gates. Any drains that will allow water to back up on the inside of the boundary will also need blocking e.g. by installing non-return valves on the outside of the boundary.
Walls: These are traditionally the most effective way of retaining water but depending on the depth of water, they will need to be built strong enough to withstand the pressure. However, a downside is that walls can be very expensive to build.
Fencing: We have designed a structural fence that can withstand up to 1m deep water and this is a more cost effective way of building a protection for your boundary.
Barriers: These can also be used but can be very expensive on a large run and will take time to install when required.
Gates: We have designed timber and metal gates that look aesthetically pleasing. They work as normal gates day to day and when required for flood protection, they have a few clamps to seal the gates.
Seepage: A combination of the above will generally stop the majority of the water. If the water is round for long enough it will affect the water table and start rising up through the ground. Any water that does get into the garden can be pumped away. Depending on the area you are trying to protect you may need to gain permission from the council and Environment Agency. This is because you will be passing the water onto somewhere else.
2. Aperture protection: This is the last line of defence, when water is at the doors and you need to stop it. There are many products available on the market such as barriers and flood doors.
Sand bags: These are usually the first thing mentioned, however in our experience, they are a waste of time if used on their own. This is because they permeable and at best only filter the water and do not act as a solid barrier.
Barriers: First of all, they are very good at doing their job but to state the obvious they are only any good when they are fitted. As a lot of flooding is flash flooding this may not be the best solution for you especially if you are unable to get them fitted in time. Also if you are going away on holiday for example and want to fit the barriers while you are away just in case, then this may advertise to the wrong kind of people that the house is empty. There are many different makes of barriers and the most suitable may depend on your property and your physical abilities to fit them as and when required. There are barriers that have no visible fixings, making them discreet. Then there are barriers that may have metal rails fixed to your property with boards or panels that drop into them to form the barrier. The rails can be powder coated to make them more aesthetically pleasing. All are available in different heights, offering protection up to 600mm deep. The last thing to consider with a barrier is storage, often forgotten about, the barriers will need to be stored in a safe location easily accessible when required and also stored in a way that will not damage any of the seals.
Doors: There are 3 types of door available: UPVC; Composite (high quality UPVC) with a wood grain effect; Traditional timber doors. All doors are flood resilient when locked and they have all been tested to 600mm depth of water. As the doors are used regularly then the seals and locking mechanisms will require maintenance, we recommend that you check them on a regular basis e.g. once a month. If there is an issue with the seals getting damaged then they can be replaced by us, do not put this off as it may affect the doors ability.
Air bricks: These will let a lot of water in if not sealed. You can fit an air brick cover, these are very good but if you have a large property with a lot of air bricks this can take a long time to get them fitted (will you have time?). The other option is to have an automatic air brick fitted, these basically close off automatically with the rising water level.
Drains and pipes: Water/ sewage backing up the drains can be a major problem. Again you can fit stop valves manually or you can have a non-return valve fitted into the main drain automatically sealing the system.
Cable entry: TV cables and phone lines are main problems, these can be sealed with a good quality mastic
Gas/electric boxes: Depending on positioning and depth of water these may need covering with a suitable barrier
Tumble dryer vents: Often forgotten but again will allow a lot of water to enter the property, Barrier protection or automatic air bricks, probably best solution is to brick up old hole at the bottom and vent out at higher point
Cat flaps: If you have a cat flap on your door you will have to fit a barrier in front of the door.
3. Seepage: If water is around for long enough it will seep through walls and concrete floors. Although water will not pour through these it will seep through so it needs to be considered. Water repellent can be applied to external walls and this will slow down the water penetration of the bricks. Water will seep through concrete floors as well, often after a property has flooded the first thing people say when renovating, is get rid of the old timber floor and fill it in with concrete. This is a solution but does not necessarily mean you have solved the problem. To do it correctly it will require a tanking membrane that covers the whole floor and returns up the walls creating a seal. But be aware, this procedure is what is used in basements and can still leak which is why pumps are used in basements. Timber floors usually have a void underneath and if you are at the stage where the timber floor has been removed you could have the walls rendered down to the sub floor with a water repellent added to the sand and cement base coat. Potentially screed the floor with the same mixture, this will then reduce the amount of water that can seep through the walls and floor. With the void under the floor you will then have a ‘well’ for the water collect under the floor rather than on top of the concrete floor. You can then use pumps under the floor to remove the water.
4. Removal: Pumps, pumps, pumps! We cannot stress the use of pumps enough. There are many different pumps available and a lot run off a standard plug or you can have a more powerful 3 phase or generator style pump. We would always recommend having a couple of pumps in your property to help control the water and there are pumps that will remove water down to within a few millimetres of the floor. Boundary protection, if water seeps through the walls, gates or rising water table in the ground the best thing to do is pump it back over the boundary. House protection, if water does get in to the property it needs removing as soon as possible, this will mitigate the amount of damage.
Things to consider when renovating after a flood: What help will you get from your insurance company? Contact them and discuss what options are available to do flood resilient work at the same time, e.g. if the front or back door is damaged and needs to be replaced, then are you able to replace it with a flood door? You may have to pay the difference but we have seen it so many times when people have had a new door fitted by the insurance company only to throw it away 6 months later to have a flood door fitted.
Step 1: After you have got past the initial shock and upset, you now need to look to the future and imagine exactly how you want to live in the property. By this we mean imagine yourself back in the property – will everything go back in its original place? Or is it time to change where things will be placed? You can then work back and plan the build effectively. Basically this means you can make correct decisions early on which will not slow down the renovation due to after thoughts.
Step 2: Think of flood resilience for the future.
Electrics: All power should be supplied from 1st floor down to the sockets, not run under timber floors as they may become vulnerable. Raise the sockets off the ground, allow for extra sockets for the pumps to run off. It is better to run any pumps off an upstairs supply. This is because often, power cuts off down stairs but remains on upstairs, this means that your pumps will keep going when you may need them the most.
Plumbing: Fit non-return valves, ideally done to the main drain but they can also be added to all small pipes e.g. shower trays - these are the lowest point of entry and can be the first to back up. Floors and walls: Fill any unwanted holes e.g. old air bricks; cable entry; tumble dryer vents. Tanking: Water can still get through! The new concrete should have a tanking membrane installed and wrapped up the walls approx 1m. Also add a water repellent to the concrete mix. The plaster walls should be replaced with a sand and cement render with a water proof additive. If you do this it should not need ripping off and replacing the next time it floods. Lime plaster, water does not affect it, but is not used much in modern buildings as it is very expensive to fit and takes a long time to dry. If you have timber floors, render right down to the sub floor, this will slow the water down and screed the sub floor with same mix as the walls.
Fit tiles to the floor and have tile skirting: This means that if you flood in the future you can mop up disinfect and get your life back to normal very quickly. If you want timber skirting boards then glue them to the walls, do not drill and fix them as you will be braking the render seal. Timber floors: Use timber floor boards not chip board.
Kitchen: Keep everything as high as possible, if you do all the above and manage to control the water to a few inches then all that will need replacing are the plinths. Allow access in timber floors to get to the pumps to be installed under the floor. General note, use solid timber products e.g. doors, skirting boards etc. We also advise for you to stay away from MDF and chipboard as water makes them 'blow' easily.
Decorating, use a good quality paint on the walls such as Dulux 'Endurance' which is washable and very hard wearing (other brands available), on wood work use oil based paints, avoid water based products on timber.
The above is only a guide to help you and is not definitive, we have learned from experience that these measures can help but other methods and products may be available. If you have any other advice you would like us to provide, please contact us.
What to do to prevent flooding
External Walls Make good to all masonry, seal up all holes, and apply proprietary colourless water resistant coating to the walls to above potential flood level. All service entry routes, passing through the walls should be sealed with proprietary sealant. The use of sealants either for the treatment of masonry or walls and/or for joints is important. Sealing masonry and walls to just above flood level prevents ingress of water into the fabric of the building, likewise joints, holes etc...Should Be Sealed Wherever Possible (Within Reason). Ideal candidates for sealing are cracks in floors and walls and other obvious points of potential ingress. There is no need for wholesale application of such products by removing skirting boards and other fixed or semi fixed fittings – that process would only be required if tanking of a property was being undertaken. Sealants should only be used to a maximum of 1m above exterior ground level.
Sealants Some sealants will bond directly to different types of substrate without the need for a primer. However, the gap should be free from dust and loose material and be prepared as described by the sealant manufacturer. The sealant should be applied so that it makes a substantial and continuous bridge from one side of the gap to the other. If this is not possible, the sealant should make continuous contact with surfaces either side of the gap.
There are many different varieties of sealant available from builder’s merchants and DIY stores. You need to select a material that will fill the maximum and minimum size of gaps. Sealants can be gun applied and/or worked into narrow gaps using an appropriate tool, and can be used to fill gaps up to 50mm wide or less than 1mm wide. For narrow gaps of less than 2mm, it may be easier to use a liquid applied penetrating sealant or surface sealant to bridge the gap at the surface. Common types of sealant include:
• Silicone - for accommodation of high movement, good for frames
• Water based acrylic - for internal, low movement situations
• Oil-based mastic - for perimeter seals to timber frames
• Polysulphide - for heavy duty applications
• Epoxy - for areas with low movement
• Polyurethane - for general purpose sealing
• Butyl - strips for compression seals
Vents and other openings All vents/ openings in walls etc...Should be protected by a removable seal or removable cover. If the opening / vent is no longer required then wide or deep gaps should first be filled or packed, for example with expanding foam or gun-applied sealant capable of filling the required cavity. The outer part of the gap should be sealed at the outside face (if accessible) and the inside faces with a sealant suitable for the size of gap, type of surfaces and expected movement. Always use BSI Kite-marked or equivalent standard products if available. The policy is to prevent water entry into the building and into the fabric of the structure. Where there is a ventilation requirement, the recommendation is to retain the vent, but protect it against water penetration, self-sealing devices or lifting the vent height are options. It is occasionally the case that, where suspended floors have been replaced with solid floors, the original air bricks have been retained and are now redundant, in such cases the recommendation is that they are blocked up/sealed. Vents are often to be found venting cupboard spaces, larders, and wall cavities, where ventilation is still required; lifting the vent outlet is a recommendation.
Waste pipes Low level drainage pipes such as dishwashers, sink outlets, washing machine pipes up to 50mm dia should be fitted with non-return valves or be lifted to pass through the wall at a higher level - greater than 1.0m above ground level.
Sewage Pipes Foul sewage pipes 100mm/110mm dia non-return valves to eliminate flood risk from the sewerage system, whilst preventing backflow, surcharging, and the ingress of rodents and insects. To BS 13564. These need fitting immediately or adjacent to the property in a manhole or inspection/rodding chamber. Toilet seal valves (often known as Toilet Bungs) can be fitted to downstairs toilets if alternative valves and fitting are not suitable.
Floors It is assumed that solid floors are water resistant and further works are not recommended. If not cracks and service entry points through the floor should be sealed with proprietary sealant.
Solid floors Many solid floors do not have an effective connection between the damp-proof membrane for the floor and the damp proof course in the wall. This means water can seep into your home through gaps at the floor/wall joint. If you are replacing an existing floor with a solid concrete floor, special attention should be given to this detail.
If the solid floor is pre 1960 there may not be a damp proof membrane, plus cracks in existing floors may allow water through the floor and replacement should be considered.
Flood Barriers to Doors suggested protection. Exterior products - Flood barrier External Fix (Kitemarked) to BS PAS 1188:2003 or BS PAS 1188:2003 The product must have been tested to a standard to PAS 1188. Independent test evidence must demonstrate the product has been tested in static water, waves, and currents and has been repeat tested. The product provider also needs to demonstrate that a quality management system similar to ISO9001 is in place. Test evidence will be required to demonstrate that the leakage rate during independent testing did not exceed 1 litre per hour per metre of aperture edge seal below the designed maximum water depth.
Flood Barriers to Windows suggested protection Protection is required to windows to BS PAS 1188:2003 or BS PAS 1188:2003 if window bottom cill is below peak flood level
Reducing Flood Risk Based upon the information collected about the property the following flood protection measures are recommended to help reduce flood risk to the property. These measures are the minimum that are required to help reduce flood risk; all measures would have to be carried out to help reduce flood risk to the property.
Pumps – Pumps are not an admission of failure, the need for pumps is based upon an expert knowledge of building construction. Regardless of how well an external wall is protected unless this is fully tanked with the floor, or sub-floor, there is always the possibility of water coming up through the sub-floor, which in the case of many older properties is simply compacted earth/ash/hard-core and even when there is a concrete sub-floor water can come up around the perimeter junction with the external walls. The pump is there to deal with water getting into the under-floor void. There is also the issue of leakage rates from flood defence products which even under the BSI Kitemarked scheme allow up to 1 litre per hour per metre of aperture edge seal below the designed maximum water depth.
Having said that this isn’t an admission of failure, where there is reliance upon householder fitted defences, there is the possibility that a) they will not be put up in time or b), they will not be fitted correctly, in either case the pump may help lessen the problem.
The surveyor in this case speaks from experience in that, at my own property, even having door barriers installed and the property being tanked to 0.9m, water still found its way into the ground floor area. Our recommendation (classed as desirable) is to have to hand a surface mounted electric submersible pump or a self-powered model. Surface mounted pumps sit at floor level and pump down to a few millimetres.
A typical specification for this type of pump is - Pumps are for clean water designed to drain domestic applications, empty and dry flooded rooms, basements, draw water from wells, basins or cisterns. The pumps are ideal for limited spaces. Complete with integral float switch, which can be selected in automatic or manual mode. In automatic mode the pump switches on when the water level reaches approx. 140mm and switches off at approx. 30mm. In manual mode the level of water can be pumped down to approx. 3mm. Maximum size of impurities 5mm. Supplied with check valve and a 1 1/4" adjustable hose connector for hose sizes 3/4" 1" and 1 1/4" and 10 metres of power cable. (other similar products/pumps are available)
Temporary Disposable Flood Protection Smart Sandbags A recent development in flood protection are bags that absorb water (up to 30 x their volume) to act just like sandbags, but don't have to be filled with heavy sand and are designed so they mould into doorways to keep floodwater out. The bags are immersed in water at the scene (or left in place as a barrier) and their semi-porous inner liner has hundreds of absorbent crystals which inflate and soak up water to for a semi rigid gel. The bags can be folded and take up a tiny amount of storage space compared to sandbags which are heavy, unwieldy and deteriorate if stored for a long time. The flood bags weigh hardly anything which solves any health and safety issues in terms of handling dead weights such as traditional sandbags.
General information relating to flood resistance measures Our experience has shown us that flood-water isn’t predictable, the fact that water entered a building through a particular point/door/opening, and from a particular side, once, is no guarantee that during the next flood event the same process will happen. With this in mind, consideration often has to be given to an ‘all round’ approach.
Sealing /sealants – This covers a multitude of potential issues. Water will track along any joint no matter how thin, or visible to the human eye, proprietary paint on coatings seals such joints. These coatings also stop water being absorbed into the material themselves, once fully saturated, brickwork or similar will allow water through. In some instances the sealing between different materials may be recommended, the open joint between an external render coat and the masonry backing is such an example.
Mortar pointing and making good to masonry – A general note is often included without being overly specific to a particular area/location, this is to ensure that no area is missed.
General Advice We advise that if the recommended measures in this report are put into place, the property will have a higher level of flood protection. It is expected that the flood protection products will be fit for purpose and are installed as per the manufacturers requirements or even fitted by them. Some of the products specified above are suitable for DIY installation although in certain circumstances professional help will be required.
Groundwater For property owners, the precautions that can be taken against groundwater flooding specifically are limited. If you have a basement which is frequently flooded and you would like to use it for storage or as a living area, it may be possible to ‘tank’ it. This involves sealing the basement with a water-proof membrane. The use of pumps in properties with ‘suspended floors’ is a recognised procedure for preventing flooding. These pumps are usually submersible models activated by float switches and can be set to automatic mode. Pipes and other cables might need installing. Access to the sub floor such as a hatch will be needed for installation and maintenance purposes