foundations for garden workshop near enbankment

[b21playa]

Hi all

My brother-in-law's house backs onto a canal and he wants to build a shed in the garden.

Is there anything different to normal strip footings (800mm deep) that needs to be done? Or would raft foundation be better?

He was going to do prefab first, but its working out expensive, and he would rather spend money on a solid one made from blocks/bricks

Thanks

 

[pinenot]

I think the lack of responses may be due to the nature of the requested info, so I wonder if you could clarify a few things.
First: when you say build a shed, could you expand on that.
Second: how close to the canal bank are we talking and is the bank built up in any way?
Finally: is there anything else that could come into play i.e. planing regs., or the likes...pinenot

 

[b21playa]

I think the lack of responses may be due to the nature of the requested info, so I wonder if you could clarify a few things.
First: when you say build a shed, could you expand on that.
Second: how close to the canal bank are we talking and is the bank built up in any way?
Finally: is there anything else that could come into play i.e. planing regs., or the likes...pinenot

Hi

Sorry for delay in replying. I have taken some pictures which might help, along with a quick sketch and google map image

1. Its going to be a 25ft x 9ft workshop, which I intended building out of concrete blocks.
2. canal would be about 5-10m away. There is a private area at the bottom on the stairs, and then bank is built up to garden level.
3. Think the soil is clay


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[freddiemercurystwin]

All your photos and plan are all well and good but they're not much use, you need to produce a section, a bit like this:

Untitled

• freddiemercurystwin
• 12 May 2010
• 2

 

[pinenot]

Agreed need to produce some accurate facts and figures as well, the difference between 5 - 10 meters is a heck of a lot.
Principally the height of the proposed area above the canal bank, is where your problem area is going to be and you must look/imagine what force the structure will impose on the bank. So a bit more thought and accurate measurements and little less pics...pinenot

 

[b21playa]

I will pop around on weekend to take some measurements and draw a side profile to help explain things.

It it very close to bank, someone suggested a raft foindation may be better

I'll update on weekend

 

[b21playa]

Ive just been sent a few measurements, and put it on a quick sketch (its no CAD)

There is no wall at the bottom, just a wooden fence. Plan is the use the area thats 13foor wide to put put the workshop around 9-10ftwide as close as possible to the fence

Hope this helps slightly.

View media item 56056

 

[pinenot]

A little bit of history, how long has this banking stood in this configuration, also what's the composition of it.
For instance is it a natural rock based slope or has it been built up?...pinenot

 

[b21playa]

A little bit of history, how long has this banking stood in this configuration, also what's the composition of it.
For instance is it a natural rock based slope or has it been built up?...pinenot

Well as far as we know the house was built around 1980 and its been there since. Does not look like a rock based slope, but just built up

 

[pinenot]

OK, so now we know the embankment is stable 30 + years. I'd still like to confirm if the it's built up or an excavation for the canal. You can figure this out by looking at the house levels in the immediate local. Also an O.S. map will show this in more detail as seen here with the close packed small black lines. This tell a lot of what will have to be considered. I can give my opinion re any form of raft foundation which I would not give consideration.
Two options to consider - one: reinforcing the embankment with sheet piling or possibly gabion baskets (a engineers opinion would be useful here)- second: would be pilling, which would bring with it the problem of vibration.
With such a steep embankment, especially if it is infill rather than excavation, pilling vibration could set the entire embankment to move towards possible collapse, your local building control might be willing to give some free advice on this, more so if similar works have been done in the area.
Helical piles, new but not unknown are another type that could fit the bill, find a supplier and ask for a tech. rep. visit to establish suitability.

Cheers for now...pinenot

 

[freddiemercurystwin]

When drawn accurately (as I did earlier), with standard strip foundations the garage should exert no extra pressure upon the bank or the canal, the 45 degree line pass by it all. I don't have cad on this lappy so can't do a screen grab just yet.

 

[b21playa]

When drawn accurately (as I did earlier), with standard strip foundations the garage should exert no extra pressure upon the bank or the canal, the 45 degree line pass by it all. I don't have cad on this lappy so can't do a screen grab just yet.

How deep would trench need for the 45degree line to pass by it all? Would adding rebar to footing help in anyway?

 

[b21playa]

In the end decided to go for a wooden shed, as it was alot easier and quicker