Garden Refurbishment Project 1 - Retaining Walls & Lawn

[Damian30]

Hi,

I am planning to do a complete makeover of our 5 year old typical 'new build' garden, with the intention over the next 8 months of leveling it out, installing a new path, deck and water feature (as well as some nice borders). Being a complete novice, I would be very grateful of any advice that could be provided as I progress this project…

1. Retaining Wall

The current situation is that the lawn is very poor and slopes into a corner. My current plan is to level the garden by installing a small retaining wall in the corner. I could build the wall so that the garden is completely level but I would guess it is best to have a slight slope away from the house to aid drainage.

Q1. If I maintain a slight slope, how great does it need be? The lawn will be around 8m long.

At it maximum height the wall would only need to be 450mm high, although this height would reduce along its length as it cut into the slope. Following advice on the builders forum, I have starting digging a trench 450mm wide and 600mm deep (allowing for the first course of bricks to start at 150mm below existing ground level).

Q2. 600mm seems quite deep for such a small wall. Is this right, or can I reduce the depth of the foundations, particularly as the wall reduces to just a couple of brick courses as it cuts into the slope? I am stepping the foundations but can't seen the benefit of 600mm when you get done to just a few courses of bricks?

As I will be having a lawn right up to the retaining wall, I was thinking about using some of the block pavers I will use for the path (future project) as a header row on the wall. This would give a neat divide between the fence and lawn edge and I was then thinking of running these pavers along the entire back of the garden/lawn. As the retaining wall would not run across the entire length of the garden, these pavers would then not be a header course on the wall and would just need to be laid directly on to the ground.

Q3. If I am coming off the wall and carrying the pavers on along the fence line, what do I bed these on? I guess I would just use a thick mortar bed on firm ground but do I need to bed down any hardcore or put in a small foundation?

Having started to dig a trench, after about 200mm I started to come across a seam of pebbles on one side of the wall (so much so that one side of the trench started to collapse!). Eventually I have come across a white perforated plastic duct within the pebble seem. I can only think that it is a land drain which runs along the back of the garden.

This drain runs within 50 - 100mm of my 450mm wide trench but does cross the trench before it leaves the garden.

Q4. What do I need to protect the drain with where it crosses the foundations? Also, where the drain runs parallel with the trench, I was going to shutter the trench to avoid the cement seeping around the drain (what is the cheapest material to use for shuttering the trench)? I was then going to put back some of the pebbles which were around the drain which I have dug out as part of the foundations? Do I need to use any gravel above these pebbles to aid drainage or should I just dig over the compacted soil above?

2. Lawn Seed

After I’ve leveled the lawn, I would really like to try and grow a luxury lawn from seed. I am okay on the preparation requirements and I appreciate I am running out of time this autumn to grow from seed (but I will still have a go).

Q5. Can anyone recommend a good lawn seed producer or they are much of a muchness and I should get the cheapest one possible (e.g. from the Lawns UK website)?

Thank you very much for any advice that can be provided and apologies if the questions are a little basic.

Many thanks,

Damian

 

[Diyisfun]

I would not advise having the lawn all the way to the retaining wall, as the mower will not get to the edge. Have a small border.

 

[masona]

Loads of info here www.pavingexpert.com

 

[Thermo]

If the area being held back is turfed then there is nor real need for a slope for drainage. That is only necessary for a hard paved area. The turf and subsoil should allow surface water to drain through it.

Yes thats ott for a small retaining wall. It will not be holding back very much in terms of weight and nor will it have much weight in terms of actual masonry. You literally only need a small (300mm will suffice) but wide foundation (450mm will be fine), with the foundation going under the turfed area to stop it turning. Make sure you leave a few dry joints in the bottom course of the brickwork to allow any water to drain through and stop the build up of water pressure behind. (not a real worry anyway but best to be safe)

if it is a drain then use a bigger piece of pipe around it when you cast the foundation to protect it and allow for any movement. Just use some cheap timber for shuttering if its not going to be seen, anything will do.

If you want a luxury lawn, you will be far better using turf. it is neater and quicker. the turf has been sown on the correct soil, at the correct rate in terms of seed per m2, feed, watered and looked after. If you do want to do it by seed then most national lawn companies that sell seed will be of a good quality.

 

[Damian30]

Hi All,

Thanks for the responses - they are much appreciated.

Thermo - when you say 300mm for the footings do you mean 200mm deep of concrete with 100mm between the footing and ground level or 300mm deep of actual concrete?

Also, as the wall will cut into the slope of the garden, can I reduce down the depth of the footing as the number of brick courses reduces, particularly when I am only getting down to just a couple of courses.

Unfortunately I don't have the funds yet for a turf option but will give the seed a go and will have to re-think in the Spring if it doesn't take.

Many thanks for all your comments and advice.

Best wishes,

Damian