[phillamb168]

This is a question for the pub if ever - you guys are always a great resource for this sort of thing.

We're looking at buying 1.5 acres next to a river (flood history: severe flooding in 1513, 1626, 1635 and 1840) and the agent says that the land will most likely need a micropile foundation. What I'm wondering is, what are these things, how do they work, and can I have a finished basement with them? Is it just for foundation stabilization, i.e., "all other ground is shifting sand" or something else? I know every case is specific when it comes to land, but something general would be helpful for figuring out how we can proceed.

[euge]

Run away my friend.

[phillamb168]

Run away my friend.

Why?

[bo]

Run away my friend.

I agree with Euge. Too many unknowns and risks. Look further.

[phillamb168]

The terrain is 6,440 square meters with 300 square meters of allowed habitable construction surface, which is almost unheard of within an hour's drive of Paris, which is why we're so interested in jumping on it. I really need to know what specifically is questionable about this. A 300m2 house with more than half a hectare of land will be worth upwards of 600,000 euros - once built it's more than 100% increase in value of the property. I'm not looking for affirmation, but I just need more than "don't do it."

[weithman5]

for this type of investment it is worth getting a LOCAL professional civil engineer that would be able to do the design.  pay a consult fee and ask what would really be involved.  Then, like i say so often, get a second opinion. it is worth spending a little dough boy (notice how i worked the brewery in to this) to get the details

[phillamb168]

for this type of investment it is worth getting a LOCAL professional civil engineer that would be able to do the design.  pay a consult fee and ask what would really be involved.  Then, like i say so often, get a second opinion. it is worth spending a little dough boy (notice how i worked the brewery in to this) to get the details

Would a general contractor generally (ha) know of someone?

[bo]

The terrain is 6,440 square meters with 300 square meters of allowed habitable construction surface, which is almost unheard of within an hour's drive of Paris, which is why we're so interested in jumping on it. I really need to know what specifically is questionable about this. A 300m2 house with more than half a hectare of land will be worth upwards of 600,000 euros - once built it's more than 100% increase in value of the property. I'm not looking for affirmation, but I just need more than "don't do it."

There is no way anyone on this site can give you solid advice without seeing the property and even then, that person(s) need to be trained in that area. I would guess that a core sample will need to be taken to really know what you're dealing with. I doubt you'd be happy having your house float down the river.

Also, be sure to check into insurance and make sure you can get it in that area.

[phillamb168]

The terrain is 6,440 square meters with 300 square meters of allowed habitable construction surface, which is almost unheard of within an hour's drive of Paris, which is why we're so interested in jumping on it. I really need to know what specifically is questionable about this. A 300m2 house with more than half a hectare of land will be worth upwards of 600,000 euros - once built it's more than 100% increase in value of the property. I'm not looking for affirmation, but I just need more than "don't do it."

There is no way anyone on this site can give you solid advice without seeing the property and even then, that person(s) need to be trained in that area. I would guess that a core sample will need to be taken to really know what you're dealing with. I doubt you'd be happy having your house float down the river.

Also, be sure to check into insurance and make sure you can get it in that area.

I'm not looking for super specifics, just an idea of what this work entails. I had no idea until today what micropiles were, and at that it's not very clear. People build houses on crappy soil all the time (see: city of london) but I just don't know how these things work.

[corkybstewart]

Ask yourself why this land is still available within an hour of Paris.

[bo]

Google took me to this site and quite a few others. I'm sure you can find some information about micropile foundations online:

http://micropile.org/ 

[phillamb168]

Ask yourself why this land is still available within an hour of Paris.

Because nobody does DIY in France, and because most people who live in the country (this is considered the sticks here) don't want to go through the trouble of building a house, or have inherited the house they own.

[Mark G]

for this type of investment it is worth getting a LOCAL professional civil engineer that would be able to do the design.  pay a consult fee and ask what would really be involved.  Then, like i say so often, get a second opinion. it is worth spending a little dough boy (notice how i worked the brewery in to this) to get the details

Would a general contractor generally (ha) know of someone?

Your general contractor should be able to recommend a civil engineer. Like others have said, get a couple opinions before moving forward. Being on a river, the shallower layers of soil are most likely silt and sand, so the micropiles would get driven below those layers into something more solid for your house to stand on.

[phillamb168]

for this type of investment it is worth getting a LOCAL professional civil engineer that would be able to do the design.  pay a consult fee and ask what would really be involved.  Then, like i say so often, get a second opinion. it is worth spending a little dough boy (notice how i worked the brewery in to this) to get the details

Would a general contractor generally (ha) know of someone?

Your general contractor should be able to recommend a civil engineer. Like others have said, get a couple opinions before moving forward. Being on a river, the shallower layers of soil are most likely silt and sand, so the micropiles would get driven below those layers into something more solid for your house to stand on.

In the US, is it relatively common to see houses built near riverbeds? I mean, there's St Louis, for example, but I dunno on a residential scale.

[piszkiewiczp]

I found this:
Micropiles are small diameter piles that can be installed in a variety of soils from non-cohesive, poorly-graded granular soils, to cohesive plastic clays. Also known as minipiles, pin piles, needle piles or root piles, micropiles can offer a viable alternative to conventional piling techniques, particularly in restricted access or low headroom situations. A micropile foundation system may be advantageous in areas where large boulders are sporadic in the subsurface, as the small diameter micropiles may be able to be installed around such boulders. Micropiles are installed using water flush rotary drilling or rotary percussion drilling techniques. Measuring between 6 and 12 inches in diameter, micropiles consistently achieve capacities of 20 to 100 tons, with special installations up to 200 tons. Micropile drilling methods generate minimal disturbance or vibration to adjacent structures, making micropiles an excellent underpinning alternative.

I'd say that you can forget about a basement. The property probably has a high watertable and at best you'd wind up with an indoor swimming pool. Also have the contractor or civil engineer look at upstream development. A little more drainage from upstream properties can increase downstream flooding. I'm in the NW suburbs of Chicago and flooding happens more frequently to people living near the local Des Plaines river due to upstrem urbanization.