So you have been flooded - What Now?

This may seem a strange point - but it is VITAL that your home is understood. Is it a modern building, built with cement, with cavity walls, or is it an old house - mainly solid walled, built with breathable materials. This can be brick, stone, or timber frame - but the important thing to realise is that these buildings NEED to be able to release and transfer any moisture getting into the fabric. This is done by diffusion, if the water is a gas, or evaporation and capillary draw if the water is liquid. Often a combination of these two processes takes place. 

Let's assume for a moment it is an old Victorian brick or stone built house on the main street.  Water enters the building, maybe fills the cellar, and any subfloor areas, and covers floors and walls.  Once it goes down, the building starts to lose that water very quickly if it is breathable. Lime plasters and paints allow water to evaporate easily. Sub floor ventilation takes over and dries out the areas below the floors. As timber dries out, it becomes immune to rot and insect attack - dry timber doesnt need any form of chemical treatment - and treating wet timber is silly and unnecessary - any problems will go away when the timber dries.  If the house has gypsum plaster, or there are damp proofing materials present - like tanking compounds, membranes, cement pointing externally, or cement render, the wall cannot dry out.

Insurance companies go to extraordinary lengths to pay vast sums of money to 'Drying Companies' who fill your home with huge de-humidifiers, using vast amounts of electricity, and which basically dont work. They are actually a heat engine, and take more moisture out of the air than they do the walls.  Think about it carefully: If your walls are covered in cement, tanking compounds, gypsum plaster, etc., they CANNOT dry out. These compounds will trap moisture - and as you see in the rest of this website, should never be used. Damp proofing is the wrong thing, done for the wrong reasons - its treating symptoms, not causes.  Drying a house is best done by removing any form of modern, impervious coating, and then applying very gentle heat, and good ventilation. In winter, the air is normally very dry - even if its raining, the air itself contains very little moisture. Hard to get your head around sometimes, but trust me - this is the case. So good ventilation, and gentle heat, will dry the home very quickly.  If dehumidifiers are used, what happens is that surface water evaporates, but very little is removed from deep within the fabric. The house is pronounced 'dry' by the insurance company 'drying contractor', and put back together, whereupon moisture starts to appear from all over the place as more deep seated moisture slowly tries to escape.

If your own appointed surveyor is involved, (one of our team, or any reputable surveyor with extensive experience in historic buildings) he or she will recommend a breathable approach - lime plaster, or similar approaches that allow walls to breathe and allow your building to dry out whilst letting you to get back to normality. You MUST allow that breathability though, to maintain the drying - and longer term, to allow the house to breathe - letting moisture produced internally to leave the building, and poreventing any chance of condensation building up.

Surviving a flood, and making your home 'Flood Resilient' is actually not a difficult thing to do. Think about it.. If you build a swimming pool, its going to fill up with water.  If you build a dam, its going to fill with water. THAT is what all the surveyors and insurance companies are doing.

We do the opposite - we accept that the water is going to get in. OK, so you sandbag the door, you put in place physical barriers, but when they are breached, its time to relax, and let the water do what it is inevitably going to do. As everything recedes, our home needs to let go, quickly. Imagine pouring a bucket of water onto a sand castle on the beach.  The water just disappears, doesnt it?  Thats because the sand is porous - it is 'breathable'.

The magic key to surviving floods is breathability.  Letting water easily escape - not trapping it into the building fabric. Like when it rains - the pavement gets wet.. Have you ever looked at it a couple of hours later and though 'Gee - that dried out quick'?  Well that is all about breathability and ventilation - using the dry air around us to diffuse or evaporate moisture from within the walls and floors of your home. It happens very quickly - if you let it. There is a huge amount of research out there - unfortunately most of it is tied up into rather specific areas - the good folk of Historic England or English Heritage as they used to be called, have done loads of work on this, but its all badged up under 'heritage' or 'historic' buildings, or Listed Buildings.. The simple fact is that it doesnt matter whether a building is Listed or not - its old - its built the same way - with simple materials - old bricks or stone, timber, lime mortars and plasters - and they just shed and let go of water. You can hose the walls down in a house with lime plaster and it won't suffer one iota - lime plaster gets wet and just dries out. You can't damage it.  Do this to gypsum, and it disintegrates - it cannot handle getting wet.

So - flood resilience - would you use gypsum, or lime? Of course - you'd plaster in lime. Simple.. No longer is the house a swimming pool, it can breathe.

The same goes for external walls - covered in cement, they are in effect a swimming pool - take off the cement, and remove cement pointing, replace with lime, and the walls do what they did when the house was built - they breathe, and cannot get wet. If they do, they dry out again rapidly.

My cottage in Weardale, County Durham is Grade 2 Listed. It has metre thick stone walls, built with limestone and lime mortar. When the driving 60mph horizontal wind hits these walls, the rain comes straight through - soaking everythig. The remarkable thing is that the rain stops, the water stops coming through, and within an hour or two, the walls are dry again.  They would be soaking wet for months, or probably permanently wet, if they were plastered with gypsum, or pointed with cement. As it is, the cottage has stood for 200 years or more, and coped with these conditions - and is still dry. 

So - as a hitlist - what do we tell the surveyor we want?

Breathability.

Removal of all modern materials where they are affected - strip gypsum, tanking, cement, membranes, back to the wall, which should be cleaned down to bare stone or brick

Allow for drying. You CANNOT measure drying by using a 'damp meter' - it doesnt work. You need to take samples, weigh them, and drive off the water before re-weighing - or using a 'carbide test' - which does this chemically. Almost no surveyors do this, and they always get the results wrong because they are using the wrong thing - a 'damp meter' , an electric 'conductance or capacitor' meter - none of these work, and you are told the house is dry when it is not.

Drying is best done with good ventilation - slightly warmed air, blown through the building to remove mosisture from the air and expel it. Dehumidifiers do NOT work as well - they heat the air and create a lot of evaporation and condensation elsewhere in the building. And they cost a fortune to run. And they push moisture back into the wall, only drying the surface.

Once dry - AND CONFIRMED BY CARBIDE TESTING.... you can start to put the inside back to how you want.

Ideally you lime plaster - solid walled buildings need this. 

If, for any reason you cannot do this, steel framed drywall construction can be used - but DONT be tempted to introduce insulation. Dont block the cavity you create, and Dont use gypsum plasterboard unless you are prepared to lose the lot if the house ever floods again. Ideally you use a woodwool board with lime plaster instead of plasterboard.

Externally, bricks and stone should be raked out and a hot lime mortar uysed for any pointing - NOT cement, or even NHL limes, which harden over the years and become almost as unbreathable as cement.

Heritage House have a team of experts - we are all some of the leading experts in the country where it comes to moisture problems in old houses. We undertake constant research. Peter is a member of the team who have written the new RICS 'Damp Diagnosis Methodology' - the most up to date methods yet published. We understand how old houses work.  We know how to make them flood resilient.  We have worked on houses that have been flooded and made the resilient - WITHOUT destroying their breathability as in the example below. If you need help, please contact us at the Shropshire office: Contact Us