Log cabin gravel foundations - Drainage question Ask questions and find answers on a range of subjects relating to self build projects

[paul41777]

I am planning on building a 12 x 8 foot log cabin and using a gravel base with timber surround to hold in the gravel.

There is a slight slope. The top of of the garden slopes down towards the bottom end. I am therefore going to dig this out and have a small retaining wooden wall which works out to be 2 feet in height (maximum) which will go down to ground level nearer the bottom of the garden.

So i plan on using wooden timbers for the surround and fill with gravel.

My question is in relation to drainage, as this is only going to be a small retaining wall is it at all necessary?

Some guides seem to indicate using French drain pipe outside the retaining wall at the top which makes sense. However, this isn't just a retaining wall it is also a surround for a log cabin. (finished gravel pit will be a rectangle). Do you think i should also require the same drainage system within the closure of the new foundation base, is that is required? I have drawings of my plans and would make more sense but can't see a way to post them on here.

Hoping the description above makes sense! Be grateful for thoughts and advice.

Thanks in advance!

[stoneyboy]

Hi paul41777,
I doubt that a shuttered rectangle filled with a variable depth of gravel will form a stable base for a log cabin. I would also anticipate the timber on the 2ft deep side will spread outwards after a while due to the pressure of the gravel.
Regards S

[paul41777]

Thank you for your reply.

I have seen various articles on you tube video's using strong wood treated timbers to form the side walls for a gravel base with a combination of rebar to strengthen them and weed barriers and gravel to prevent against rot. Also the 2 feet at the top with the gravel pushing out will have earth pushing back on it which should cancel out opposing forces. I've attached an image of a similar one i seen online i was hoping to mirror. What would your advice be to use instead?

Also in terms of drainage do you think i should capture any water that forms within the square rectangle base or should i capture the water at the highest point before it enters the base or both? Hope that makes sense. Thanks in advance.

[stoneyboy]

Hi paul41777,
From your initial description I envisaged a base with its top edge level with the existing garden level and its bottom side raised 2ft above the ground level. If this is the case then my comments still stand.
With the fall on your garden it’s not really necessary to provide drainage. Surface water will naturally run down the slope. You could run a piece of perforated drain pipe in the gravel at the top outside your timber frame.
Regards S