Successfully Dealing with Flood Damaged Buildings

An article written by Trace and published in the PCA ‘Preserve’ magazine, (Spring 2006).

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In recent issues of Preserve I wrote related articles on methods of using modern membranes in buildings, the first advising on common damp problems and the second on Heritage building. This article will deal with remedial measures in flooded buildings, a problem my company and I really do have first hand knowledge of.

I live in Glossop in the High Peak at the bottom of the notorious Snake Pass, my house has a 60 metre garden that (thankfully) slopes down to a stream and my offices (soon to move) are a 200m walk away in the remains of an old cotton mill that backs onto the same stream. The back of my office is 2.5 metres from the same stream, exactly where a water wheel was once positioned.

One afternoon about four years ago the amount of rain falling in a short period on the hills around Glossop caused a 100 year flood, this true because it happened about a hundred years ago as well. The first we knew was that water penetrated our office via a door leading to the river at the rear and into our stores at the front. Fortunately, our office floor level was marginally high enough to block the bulk of the water with sand bags and that within the stores causes only limited damage. Neighbouring companies were not so lucky, with buildings suffering major structural damage, including floor heave, collapse of walls, ruined stock and machinery.

My garden also suffered, as did those of three of my neighbours, with what was once a ‘trickling  brook’ being gouged out to twice the width and depth, with great big slabs bedrock stripped off and tumbled down the river.

showimageOur insurers, which is an important point in this article, wanted to ‘repair’ the gardens, the stream bed and banks in the least costly manner, which none of us agreed with, but because one of my neighbours is a Structural Engineer, he was having none of it, so he came up with a scheme and undertook it himself, I believe at a total cost of £180k or so. The lesson learned was that the insurer may not always go for the best and safest repair because of balance sheet reasons.

This factor follows on to dealing with flood damaged buildings because on that fateful day about 100 houses and commercial premises in Glossop were washed out, the pattern following the many streams running off the hills into the valley, culminating in the High Street at the low end, the low point of the valley, where a long line of properties on both sides of the street suffered.

In the days following this street was lined with skips both sides, with the muddy pavements full of ruined household fittings, furniture and personal items. It really was quite shocking and surreal.

Although my company spends much time dealing with flooded basements caused by hydrostatic ground water pressure, my company is not on any insurer list for dealing with flood damaged buildings. Even so I believe we could teach them something, as all of our members no doubt could.

In the following months and trailing off after about two years, the damaged houses and commercial buildings were all stripped out, repaired and brought back into occupation by flood repair specialist contractors employed by the insurers, most. However, to this day I regularly see the same contractor vehicles outside one or another of the buildings, presumably undertaking some form of snagging. Sometimes I don’t need to wonder what they are doing because I see bags of plaster, none of which I would dream of using in dealing with dampness!

showimageInitially Trace only undertook flood repair in six properties out of the 100 or so that were damaged, all cases where people knew us or where they took independent advice. We (again) simply used cavity drainage membranes to design the problem out of the equation, mostly meshed so that plaster profiles were maintained. This allowed the isolated substrates to dry out gradually in their own time and all have been successful. In all six cases the customers had to accept a lower payment from the insurer based on what their own contractors quoted, paying Trace the ‘’betterment’ out of their own pockets for the peace of mind we provided.

We are now regularly called to advise on other flooded properties where latent dampness has occurred, with a whole gamut of problems, such as bridging plaster, lightweight blotting paper plaster, rusting angle beads, etc. etc., and each time we again simply replace with cavity drainage membranes.

When will they learn? The facts are that if one uses cavity drainage membranes, then ‘drying out’ occurs instantly and ‘fitting out’ can occur safely, with the wet substrates left to gradually dry down to equilibrium safely. Such repair would normally be undertaken after initial drying out has occurred anyway, leaving only final dry down outstanding, just that time when all the impurities in the structure move out to contaminate all of those direct applied plasters.

As an aside, the power of the flood caused many basements in the town that were not compromised by water off the land, and that had never flooded in living memory, to since become more susceptible to flooding through the walls because of hydrostatic ground water pressure. I can only surmise that the water washed out below ground pathways.