house on slate out crop problem or not?

[what..the?]

Hi there I have been looking at a house to buy which is by a beach, the house is up a hill which has exposed slate areas, so one would assume the hill/outcrop in mainly slate.

With the beach and a river/steam close at the bottom on the hill there is a risk of flooding in the years to come as rises in sea levels and worsening weather conditions take effect. The water table seems already high with areas of grassy fields extremly close to the house at the bottom of the hill being under water regularly. The house as it stands though is up this hill and so very unlikely to be flooded out itself but my concerns would be

A) is a house built on a hill made of mostly or partly slate a problem? I saw an exposed section of slate behind the house the other day and water was almost running out of it?

b) would a slate hill be effected, if it were to be flooded at its base, would it lose stability or erode badly there's currently tarmac concrete and stone walls at the base of the hill, there are no obvious exposed slate sections at the base. which may be worth pointing out.

Thanks in advance

[buildersmate]

There's an awful lot of bunkum spoken about the impact of global warming and what it does to the risk from flooding.
Slate is a metamorphic rock. It is hard and reasonable stable except when subject to frost action when it sheers. It is also impervious to water so the water must be running from the strata just above the line of slate. In any event, you really must have a survey done on the stability of the house's foundations if you have any concerns or their is any evidence of cracking on the walls.
Flooding - there are three things to think about - all different.
Rise in ocean levels: at worst this could be of the order of a couple of tens of metres - disastrous if you live on a Pacific atoll - no big deal if you are in western Britain (where most of the slate is to be found) and at least 30 metres above sea-level.
Flooding caused in river valleys that experience huge volumes of water over a long period upstream. I'm talking about the likes of Tewkesbury near Worcester, or Cockermouth. This is an issue when one lives in the natural flood plain say within 10 metres of the normal river level. The land here is invariably flattish, and the problem arises because the natural flood plain has been built on. This is unlikely to be an issue for you.

[buildersmate]

Run-off, impacting your property. This is of the type experienced at Bude in Cornwall. Vast amounts of water falling in a very localised area, swamping the small streams in a relatively narrow valley (where the water has no place else to go). You need to assess where such water might originate and where its natural flow course would be. I have friends in Devon who were impacted by this. They live on the side of a 1 in 6 hill. The water swept down the lane, over a small bank, into their property and through the other side back into the public lane, filling the garage to a depth of 3 feet. Tonnes and mud and tree debris were left on their land. No-one in 50 years had ever known anything like it.
This is the most likely potential source of any problem for you.

[what..the?]

Thanks buildermate yes this house is just off a beach in cornwall a river does came very close past the base of the hill and out to sea but this river has a huge output because of it's large water catchment from open hills, fields and woodland, above in the valley with the already high water table and the flat land next to the river which is aready under water most the year, it is very lightly this will get worse over the years unless the council work on the land they own next to the river. Therefore I can see the base of the hill being under water. Not this house because it is on the flood risk area but too high.

There is a risk though of run off from what you say becasue the hill in quite large but we would be a the bottom end on the hill one of the last houses on the hill so we could get the run off from all the hill and down the road made worse by concreted developments increasing the run off and lack of absorbsion. There is also a dug in driveway/carpot at street level which we would want to make bigger I think we would have to consider putting some drainage runways in to try and get the water to bypass are dug in carport and go round other wise it could flood out and cause errosion inwards into the garden.

[what..the?]

This stability survey would that be in a normal survey or would that be a special additiional survey

I just got a HIP report and it doesnt seem to help to much it states about water drainage but that means waste water and where it goes. it asks the owners (I assume) questions when asked have they checked flood risk from the government website it says no they haven't which is no real surprise because it shows the flood area just falling short of the house at the lower margins of the hill. It doesnt state anything about stability or run-off I suppose it doent have too. It asks has there been a flood, storm of rott damage they say no. But they could be lying couldnt they?

Radon is in the area as it is common in the south west is this a problem, would a survey pick up a serious level.

[buildersmate]

There is a standard question that your legal conveyancer normally asks about 'has the property ever experienced flooding to the knowledge of the vendors'. To answer 'no' to that knowing it to be untrue could open the vendor up to future legal action from a buyer if a situation later arose.
Why not talk to locals in the area who have lived there a long time about their experiences in the past? - they have no axe to grind. That is a good indicator, but not completely foolproof - nothing similar had ever happened in Boscastle before the famous flood.
Surveying only assesses the immediate property.
Radon testing is a specialist environmental survey one can have - at a one-off cost. Plenty of organisations offering such testing in the area.

[what..the?]

thanks alot for all your help buildersmate, your great