How to Make... a Property More Flood Resistant

Hello and welcome to Hazard + Hope!

I'm Ed and

in this episode we're going to be looking at how to design and adapt

a property to be flood resistant.

So here we go...

This episode of Hazard + Hope is sponsored by  Yorkshire Flood Resilience.

So, first and foremost...

what do we mean by flood resistance and why is it  needed? Well essentially flood resistance measures

at the property level can help to restrict water  entry into a building and minimize the huge amount  

of the damage and disruption to properties and  people's lives that floods can cause.

Flood resistance is one of a range of approaches within  the remit of Property Flood Resilience also known as PFR.

Now in terms of guidance in this area, the  Code of Practice for Property Flood Resilience is  

crucial to be aware of and you can check out  the episode that we've made about it here,  

we've also put the link to the Code of Practice  just below the video and it essentially sets out  

the key process and standards through which we  should be undertaking PFR in relation to both  

new build and existing context and it applies to  both residential and commercial contexts and for  

multiple as well as single buildings. Now in  this episode we're going to be looking at flood  

resistance measures but we have also made an  episode on flood recoverable approaches that  

you can check out here, which actually looks at  the ways in which we can design a property so that  

if or when flood water comes inside it that  there's minimal damage to the building's fabric  

or its contents. We're also making an episode  on avoidance-based approaches for PFR and  

that includes things like raising floor levels  changing the location of habitable areas or  

even adjusting the vertical horizontal position of  the building itself. But back to flood resistance  

now the Code of Practice defines it as 'the  use of materials and approaches to manage  

water entry into the property' so as I said this  approach really is about excluding water entry  

and that can be done through things like flood  doors or deplorable flood barriers.

First and foremost though a couple of disclaimers about this  approach. Okay so it's not necessarily going to be  

suited for every construction type or flood risk  context and the performance of any measures will  

of course be reliant on them being correctly  specified installed managed and maintained  

over time but really many of the measures  that we're discussing it can be incredibly  

effective at helping to prevent and slow the  rate at which floodwater enters a building.  

As you can see here there are many different ways  in which floodwater can enter a property I mean it  

doesn't just have to be through the front door you  know it can seep in through party walls, surcharge  

through drainage systems and rise up from beneath  the building and if any one of these hasn't been  

addressed then it can lead to the strategy being  undermined and the property flooded.

So first of all I'm going to go through the different types of  flood resistance measures that are out there and  

then I'll discuss the process and key questions  to consider when selecting a particular approach.  

So what types of flood resistance measures are  there? Well first of all there are ways to make  

the perimeter of a site or area flood resistant  and help to protect the property from flooding  

that way... this can include measures such as  permanent flood walls deplorable barriers and  

these might be framed or self-deployable. However  it's important to be aware that these types of  

external perimeter protection measures can  push the problem elsewhere they can take  

time to construct and assemble and may need to be  built with appropriate structure or foundations  

and they can be flooded from behind. But in  this episode we're going to primarily focus  

on resistance measures for the property itself  and when you think about ways in which floodwater  

could enter a building there are a number of  different ways in which we can protect these  

different apertures. For example you've got things  like flood doors which look like a normal door but  

are designed to help restrict water entry  up to a given depth there are also a range  

of different types of deployable barriers now  these can vary in size and width for material and  

it can be single objects such as large solid  barriers that can be clipped into place or dropped  

into mounting brackets or they may actually be  made up of multiple repeated elements such as  

individual boards that are slotted into a  housing the mounting systems can vary but they're  

typically fitted onto the external face of the  aperture such as a doorway. But you can also get  

ones that are actually wound and expand in place  to adapt and fit the internal breadth of a given  

opening. There are also mechanical and automated  types of deplorable barriers such as ones which  

rise from the floor, hinged ones and roller  barriers that can come down from above.

What's important to consider with these is that there  really isn't anything which is obstructing the  

deployment of them. Now flood barrier products on  a property can typically restrict flood waters to  

depths of 30 to 60 centimeters and there are ones  which do work to higher levels but beyond that  

level the amount of hydrostatic and hydrodynamic  loading on a building can be significant and so it  

can be safer to actually let the water in and rely  on the property being flood recoverable.

However, there are resistance measures such as flood  skirts which can actually hold water depths out  

up to about 1.2 meters but their performance  is of course dependent on them being used in an  

appropriate context and on properties where  the structural reinforcement of the walls  

can be required to cope with the significant  forces that are at play at those depths.  

You can also specify flood resistant windows  which which typically have non-open wall glazing  

at lower levels but remember that there can  be some very large elements of debris that are  

picked up and carried by flood water... that could  be trees or cars and when they're smashing into  

the windows and openings there can be significant  forces at play so, so you may choose to actually  

block up an opening and raise it to a slightly  higher level just to reduce that risk.  

As well as openings in the properties  and walls, flood water can of course  

come in through air bricks at lower level in  terms of resistance measures for these there are  

a number of different products to consider. So you  can use manual covers that you actually clip on  

before a flood and you can also get these for  things like weep holes to stop water getting  

into a cavity wall or it might be that you  actually specify and fit an automatic air  

brick which actually closes as flood water rises  but these do need to be cleaned and maintained as  

debris and even cobwebs can cause them to remain  partially open and reduce the effectiveness of  

their performance. Now another resistance  measure to consider is non-return valves  

and these can be fitted to the drainage and water  channels for things like washing machines showers  

sinks and they enable the one directional flow  of water which essentially helps to limit the  

amount of flood water that can surcharge and  backflow through a system. But it can also be  

that you fit things like bungs to toilet to act  as a sort of second line of defense and extra  

resistance measure. Now, given that flood water  can penetrate property through cracks in mortar  

or absorption through the material itself it can  also make sense to treat the external building  

envelope with sealant or flood resistant renders.  Now, sandbags are of course another type of flood  

resistance measure but be aware that they can be  unstable and leak if not built correctly, they can  

take time to fill and construct although modern  non-sand versions are available and will actually  

expand on contact with water and post flood but  they do require appropriate disposal to avoid  

contaminating the surrounding ecosystems. With  any of these types of measures the cannon always  

will be a degree of leakage so the last measure  to mention is actually pump and sump systems.  

Now these aren't strictly preventing water entry  and such but they can be vitally important to  

be used in conjunction with resistance measures  as they'll help to get any water out that has come  

within the building and it's really crucial to  specify the right size and number of pumps and  

consider where they're positioned in the building  and the location of the potential outflow  

where possible there should be a backup power  system. So that might be a generator but you know  

power cuts can occur in the event of a flood and  you can also get flood alerts and alarms that will  

actually send you a text and let you know if and  when that sump and pump has been activated.

Now, there are of course new products being developed  all the time but that's just an overview of some  

of the different types of flood resistance  measures that are out there at the moment and  

whilst it's tempting to kind of cherry pick and  mix and match potential measures it as I mentioned  

earlier not all house types and flood risk  contexts will be suited for resistance measures,  

so when considering options there needs to be  a rigorous understanding of the flood hazard  

and the property set up as it's set out in the  Code of Practice and this is vital information  

as it helps to inform the specific types of PFR  strategies that could be suited. There are many  

forces that are at play when a property floods,  now... each type of flooding will have different  

characteristics and vary in terms of its rate of  onset, duration, frequency the depth and the types  

of debris that are actually carried within it and  understanding the potential frequency and severity  

of flood depths can help inform an appropriate  height for flood resistance measures to provide  

protection up to. Choosing these thresholds  is important as you also need to bear in mind  

what the future flood risk context could be and  actually how much change to allow for.

Next, it's important to review which building elements  or apertures on the building could actually  

require protection and that goes back into  understanding and identifying the potential  

points of water ingress. A key factor to consider  is of course what the building is made of and  

whether external wall finishes will be actually  suited to resist flood water for prolonged  

flood durations and you do also need to consider  whether the property type is actually suited for  

resistance-based approaches so is it detached  or is it part of a terrace I mean it can make  

sense for PFR strategies to be undertaken  in conjunction with neighbouring properties  

so the design strategy actually works on them as  an individual unit rather than flood water flowing  

between party walls. So, context is key but we  do also need to be aware that on many properties  

there can have been extensive alterations and  extensions made over time and that these can  

be weak points which could potentially  undermine a resistance-based approach.  

Planning and conservation policies can also limit  the type of resistance measures that are able to  

be used on or around a property. So flood walls  for example can require planning permission and  

even modelling to be sure that it's not pushing  the problem elsewhere and that they function  

correctly... and if it is agreed that resistance  measures are suitable for your property for your  

context then the next thing to consider is whether  they're actually active or passive measures which  

are specified. So, an active flood resistance  measure is one that requires somebody to  

actually manually fit or deploy it, whilst passive  measures are fitted into the building already and  

they work without such interventions. Now,  given that flooding can occur at any time of day  

night or year passive measures can be preferable  but it's obviously dependent on the particular  

circumstances and the user requirements and  those end user preferences are of course vital to  

understand and inform the specification of PFR...  you know you need to think, will they be able to  

lift and fit that flood barrier in place if and  when need be. It's also important to consider  

what mechanisms or systems can be put in place to  be sure there's enough advanced warning in order  

to deploy active measures, flood alarms can be  helpful in that regard but it can also be useful  

to have a number of people trained and up to speed  on how particular resistance measures need to be  

fitted. Now, from a style or aesthetics point of  view there are many different types of flood door  

and flood barrier that are available and more are  coming to the market all the time but essentially  

I would say that they don't have to stick out like  a sore thumb there's some nice ones out there.  

When it comes to the performance of different  resistance measures, at the time of recording this  

episode there isn't a single industry standard  resilience rating as such for PFR but there  

are a number of different BSI standards  and Kitemarked products on the market and  

there's a link for more information about these  on the description just below this video. But  

with these types of resistance-based approaches we  we also need to consider how somebody would safely  

evacuate the building before during and after a  flood event... because some resistance measures  

may need to remain in place for weeks on end as  grounds remain saturated and the floods could  

come again and something like a flood door can be  particularly effective in these instances as it's  

able to be used as a normal door but in the event  of a flood it's there to perform as a flood door.  

The selection and specification of resistance  measures will of course be influenced and  

beholden to the cost and the budget available and  over the last few years flood resistance measures  

have become much more affordable and there can  be grants available to help with the purchase of different measures.

I would say that there's also  an increasing movement within the insurance sector  

to reward resilience.

During the construction  and commissioning phases of the Code of Practice

there are a number of different steps and checks  that are set out to ensure that measures have been  

correctly installed. I mean it's optional but this  can also include wet testing where you actually  

put a jig around something like a flood door and  you fill it with water and check and test the  

seepage rates... and that awareness of the PFR  approach in place needs to be enduring because  

if a property was to change hands the  new owners need to be up to speed on  

why particular materials and measures have  been specified as if they're not there's  

really a risk that they could be ripped out and  removed or have their performance impaired by  

other alterations. So as the Code of Practice  sets out a handover pack needs to be passed on  

to provide this information and it's not just  the bricks and the mortar that will need to be  

adapted any successful PFR setup will need to be  operated and maintained in the right way.

So with resistance measures there will need to be regular  checks on things like seals and and actually the  

users know where their barriers are stored and how  they need to be fitted and as Katie who features  

in one of the Our Flood Resilient Home episodes  put it, 'if you don't maintain it that flood door,  

is not a flood door anymore' and that mantra and  mindset really applies to the whole remit of PFR  

if there's not been a flood for 10 years, would  you know where that flood battery is stored and  

and how it is fitted or whether the sump  and the pump is still in full working order?  

It doesn't have to be a one or the other approach  when it comes to resistance and recoverability,  

they can be used in conjunction to great effect  and diversity is certainly a key characteristic of resilient design. 

Because I would say that in  any context there's always going to be a degree of  

residual risk and you wouldn't want to necessarily  be reliant on the performance of a single  

threshold to keep your property safe and as the  Code of Practice sets out your resistance measures  

should be designed to 'resist flood water up to an  appropriate depth include a mechanism to allow for  

the measure to fail or over top safely so it does  not present additional risk to the property or the  

inhabitants' so in something like a flood door  the letterbox can actually function as a way of  

letting that flood water into a property once it  reaches the given threshold and have the interior  

of the property is flood recoverable so there's  less damage if and when the water comes within.  

Now, a lot of the discussions so far have been  around the idea of retrofitting or upgrading  

these flood resistance measures onto an existing  property but these can also of course be specified  

and fitted onto new build properties. What I would  say though is that we might not expect to see a  

new build property having its flood resistance  measures put to the test by flood water from day  

one as what that could mean is that the property  has been poorly located or that its finished  

floor levels and habitable areas have been set  to the wrong threshold.

So why should you make your property more flood resistant?

Well, if you look at Sue's episode of Our Flood Resilient Home, 

I mean the flood boards that she uses helped to  significantly slow the rate at which flood water  

entered within her building and she's got  non-return valves there and something pump  

in place to get the water out of the building  it was the difference between her home taking  

10 months to repair and reinstate at a  cost of 70,000 pounds for the insurer  

and being largely unaffected by the last flood bar  a pot of varnish and some mopping out...

you know that contrast is incredible and it shows you the  value and effectiveness of flood resilient design.  

So if you think you'd like to make  your property more flood resistant then  

what's the next step? Well the Code of Practice  shows the process through which you need to  

go through. Really the first step is to get  advice from a suitable professional on your  

flood hazard and the property setup so they can  help inform you of what options may be suitable  

for your given context and preferences and if  that happens to be that resistance measures  

aren't appropriate for your context or  setup then you don't lose faith because  

there are many other ways in which we can design  and adapt properties to be flood resilient and  

minimize the damage and disruption that floods can  cause and speed up any recovery times.

So thanks very much for listening and if you'd like to keep  updated on future episodes,

please subscribe below hit the bell for notifications and  we look forward to seeing you soon!

you