Posted: Sun Jan 19, 2014 5:57 pm
I am looking for a bit of experience / expert advice on my plans and possible options. I have read so much on this subject from many forums and expert web sites so am nearly there…. But have some specific questions before I spend lots of money and break my back! So sorry for the long description!
Usual story, Garden flooding, clay subsoil!
The garden (12m * 27m) slopes away from the house by 2ft over 27m. All adjacent gardens are higher at the bottom where my garden’s lowest point is. At this point the clay starts about 18 inches below the top soil.
My plan to improve the situation is as follows:
1. Install a large 200- 400lt approx perforated sump chamber 1m deep at the lowest point. support the circumference with 20mm gravel for as large an area as practically possible. This will the centre point of water collection supplied by ground water and French drains.
2. Install network of French drains approximately 2ft deep with 100mm perforated land drain pipe throughout the garden and connected to the Sump. All backfilled with 20mm clean gravel before laying (sand?) topsoil / grass. (whats the most efficient thickness of soil and grass for the perfect lawn!)
3. The sump will be ‘Pumped’ out to ‘the front garden create soakaway’ where it will naturally find better drainage – I am aware of the restrictions of connecting land drainage to United Utilities foul waist.
Questions:
1. what’s the best product to use for the sump container? I can get civil products from £100 + vat ish but want to save money…..Was thinking about 4 large old car tyres bolted together and I will make lots of small holes in it!
2. What is the most reliable 'brand' and diameter land drain pipe to use?
3. 20mm gravel? Is this the best / cost? what material is best for Backfill of posh French drain?
4. THE PUMP…. Is it worth spending the money and getting a Zoeller submersible grey water pump - 53-0065U for £200 ish or a £80 one from screwfix? I want the Zoeller, but i have to Justify cost against the budget!
5. I am going to keep ‘on site’ the top soil that is extracted for use again as top soil. All clay excavated will be removed.
I am planning to raise the level of the lowest part of the garden by 450mm at the thick edge of the Wedge. 90sqm (Effectively leveling the area to a fine edge - area calculations should be x0.5.)
The big question is.......once the infrastructure has been installed and the ground has been prepared, Should I also lay a 100mm (or more?) layer of gravel on top before newly laid top soil to increase / improve the water transport to the French drains and hence to the sump for removal?
6. Should I consider using soakaway creates while still relying on a pump?
7. Should I be using membrane sheeting around the land drainage pipe? Brand / Specification?
8. AM I ON THE RIGHT TRACK?
Any help will be most appreciated. I need to get this work completed before I start building a 34sqm extension to my house in the spring. The building part I can do!
I just need your experience in drainage! And thank you for reading this!<span style='font-size:19pt;line-height:100%'></span><span style='font-size:19pt;line-height:100%'></span>
Usual story, Garden flooding, clay subsoil!
The garden (12m * 27m) slopes away from the house by 2ft over 27m. All adjacent gardens are higher at the bottom where my garden’s lowest point is. At this point the clay starts about 18 inches below the top soil.
My plan to improve the situation is as follows:
1. Install a large 200- 400lt approx perforated sump chamber 1m deep at the lowest point. support the circumference with 20mm gravel for as large an area as practically possible. This will the centre point of water collection supplied by ground water and French drains.
2. Install network of French drains approximately 2ft deep with 100mm perforated land drain pipe throughout the garden and connected to the Sump. All backfilled with 20mm clean gravel before laying (sand?) topsoil / grass. (whats the most efficient thickness of soil and grass for the perfect lawn!)
3. The sump will be ‘Pumped’ out to ‘the front garden create soakaway’ where it will naturally find better drainage – I am aware of the restrictions of connecting land drainage to United Utilities foul waist.
Questions:
1. what’s the best product to use for the sump container? I can get civil products from £100 + vat ish but want to save money…..Was thinking about 4 large old car tyres bolted together and I will make lots of small holes in it!
2. What is the most reliable 'brand' and diameter land drain pipe to use?
3. 20mm gravel? Is this the best / cost? what material is best for Backfill of posh French drain?
4. THE PUMP…. Is it worth spending the money and getting a Zoeller submersible grey water pump - 53-0065U for £200 ish or a £80 one from screwfix? I want the Zoeller, but i have to Justify cost against the budget!
5. I am going to keep ‘on site’ the top soil that is extracted for use again as top soil. All clay excavated will be removed.
I am planning to raise the level of the lowest part of the garden by 450mm at the thick edge of the Wedge. 90sqm (Effectively leveling the area to a fine edge - area calculations should be x0.5.)
The big question is.......once the infrastructure has been installed and the ground has been prepared, Should I also lay a 100mm (or more?) layer of gravel on top before newly laid top soil to increase / improve the water transport to the French drains and hence to the sump for removal?
6. Should I consider using soakaway creates while still relying on a pump?
7. Should I be using membrane sheeting around the land drainage pipe? Brand / Specification?
8. AM I ON THE RIGHT TRACK?
Any help will be most appreciated. I need to get this work completed before I start building a 34sqm extension to my house in the spring. The building part I can do!
I just need your experience in drainage! And thank you for reading this!<span style='font-size:19pt;line-height:100%'></span><span style='font-size:19pt;line-height:100%'></span>
