Posted: Thu May 25, 2006 4:23 pm
I'm just about to start work on laying a patio, and I'm buying all my materials from Wickes (maybe that's lazy of me but I'm on a tight budget and I know what I'm getting). I'd like some advice for a couple of things, just to make sure I'm heading in the right direction.
My garden has a slope, so I'm going to be building a retaining wall (about 3ft high). However, years ago when I had 'other ideas' I laid down the foundations I'll be using, which are only the width of one concrete block (laid flat, ie 215mm). What I want to build now is a retaining wall using concrete blocks as if they were bricks, ie also laid flat, in a brickwork pattern. Then I want to build the visible wall just in front, from Wickes pitch face walling.
The retaining wall seems okay, but I need new foundations just in front of it for the pitch face walling. I need to dig under the grass line, which I didn't do for the original foundations, and is another reason I don't want to put the pitch face wall on the original foundations - there's a line of blocks there already, which would be forever visible if I added the facing wall on top.
Still with me?!
What I'll end up with is a breeze-block wall, with a 'nice' wall in front, but I may end up with a small gap between the two. Should I fill this in as I go, ie with the mortar used for the front wall? Or should I just back-fill it with earth when it's all done? I don't want the thing collapsing or cracking from freeze-thaw, so I'm thinking of just buttering the back of the pitch face walling and sticking it on in that way.
However, what I'm wary of is that this will give me a solid concrete barrier, so draining will be pretty much minimal. Should I build in some lengths of copper pipe through the retaining and front walls for drainage? Alternatively I could drill holes through both walls (probably easier, then I wouldn't have to work around the pipe). How many drainage holes do I need? Do I need any at all? And how far up should they be? Ie do I put them all near the bottom or part/half way up? What other things should I be taking into consideration?
Second thing: to back-fill behind the retaining wall, I'm using earth that I dug out when building the foundations for my shed. I have a least 4 or 5 tonnes of it - it's a big shed!
Problem is that I have clay soil that an amateur potter would die for, and whereas in the ground it was compacted, now it's dug out it's all loose again (mixture of sub-soil and huge lumps of solid clay). I'm going to take out as much of the solid clay as I can, but my plan is to backfill my retaining wall about 6 or 8 inches, then manually ram it down to compact it, add more, ram it down, and so on until I get to the top (about 3 feet in all). Is this a good idea? I'm trying to stop it settling later. I want to compact it manually - I have an 'earth rammer' (I forget the real name!) from Wickes. A Wacker plate would be better, but I like to take my time with jobs - I flag after about 4 hours - so doing it manually is the only option (unless I rent a Wacker for about a month!)
On top of that, I have planned to put a layer of Wickes 'Driveway Fabric' followed by 100mm of MOT Type 1 sub-base. The Wickes catalogue says the Driveway Fabric 'prevents substrate from collapsing...' etc, which from the Paving Expert pages seems to mean the 'pumping' of stones down into my clay soil. The site does say not to use ordinary landscape fabric (which I won't), but will this stuff do the trick?
Am I right to do this, given that I have soft clay soil, even though I'm going to do my best to ram it down? The expense isn't an issue (it's not that pricey anyway), but I just want a bit of reassurance that I'm doing all that I can to stop the patio from sinking.
On top of that I will be mortaring the slabs one by one on a full bed of mortar (not the five dots in the corners/centre) to make it all as solid as possible. That one has been drilled into me by Tommy Walsh!
Last thing: the patio will end up being about 8m wide and 5.4m out into the garden. That seems to me like it's going to be catching a whole load of rainwater which will have to go somewhere. The somewhere in this case would be over the edge onto the garden.
While I will be sloping the patio away from the house, I'm not sure about the effect that amount of water will have on the grass below. I could make it slope sideways as well, but not sure if the neighbours will thank me for it! There are no drains to feed into in the garden, although there is one drain cover at the far side of the patio area - is this my most likely 'plug hole' and should I steer the water towards it?! My skills with the spirit level do not give me great confidence that I would be able to do this sucessfully without channeling water back towards the house!
An alternative would be to have a 'ditch' at the foot of the patio wall, filled with a fair amount of gravel/shingle, which could be used to soak away my mini-waterfall. I like the sound of that, actually - just thought of it as I was writing!
I'd appreciate any feedback you can give me on this. I don't mind 'over building', as I'd rather do more than I need in a week's work than suffer for years as it all sinks in and falls down! If it were up to me I'd be back-filling with concrete, not soil!
Cheers
Nick
PS Sorry for the essay, I just wanted to make sure I covered everything!
My garden has a slope, so I'm going to be building a retaining wall (about 3ft high). However, years ago when I had 'other ideas' I laid down the foundations I'll be using, which are only the width of one concrete block (laid flat, ie 215mm). What I want to build now is a retaining wall using concrete blocks as if they were bricks, ie also laid flat, in a brickwork pattern. Then I want to build the visible wall just in front, from Wickes pitch face walling.
The retaining wall seems okay, but I need new foundations just in front of it for the pitch face walling. I need to dig under the grass line, which I didn't do for the original foundations, and is another reason I don't want to put the pitch face wall on the original foundations - there's a line of blocks there already, which would be forever visible if I added the facing wall on top.
Still with me?!
What I'll end up with is a breeze-block wall, with a 'nice' wall in front, but I may end up with a small gap between the two. Should I fill this in as I go, ie with the mortar used for the front wall? Or should I just back-fill it with earth when it's all done? I don't want the thing collapsing or cracking from freeze-thaw, so I'm thinking of just buttering the back of the pitch face walling and sticking it on in that way.
However, what I'm wary of is that this will give me a solid concrete barrier, so draining will be pretty much minimal. Should I build in some lengths of copper pipe through the retaining and front walls for drainage? Alternatively I could drill holes through both walls (probably easier, then I wouldn't have to work around the pipe). How many drainage holes do I need? Do I need any at all? And how far up should they be? Ie do I put them all near the bottom or part/half way up? What other things should I be taking into consideration?
Second thing: to back-fill behind the retaining wall, I'm using earth that I dug out when building the foundations for my shed. I have a least 4 or 5 tonnes of it - it's a big shed!
Problem is that I have clay soil that an amateur potter would die for, and whereas in the ground it was compacted, now it's dug out it's all loose again (mixture of sub-soil and huge lumps of solid clay). I'm going to take out as much of the solid clay as I can, but my plan is to backfill my retaining wall about 6 or 8 inches, then manually ram it down to compact it, add more, ram it down, and so on until I get to the top (about 3 feet in all). Is this a good idea? I'm trying to stop it settling later. I want to compact it manually - I have an 'earth rammer' (I forget the real name!) from Wickes. A Wacker plate would be better, but I like to take my time with jobs - I flag after about 4 hours - so doing it manually is the only option (unless I rent a Wacker for about a month!)
On top of that, I have planned to put a layer of Wickes 'Driveway Fabric' followed by 100mm of MOT Type 1 sub-base. The Wickes catalogue says the Driveway Fabric 'prevents substrate from collapsing...' etc, which from the Paving Expert pages seems to mean the 'pumping' of stones down into my clay soil. The site does say not to use ordinary landscape fabric (which I won't), but will this stuff do the trick?
Am I right to do this, given that I have soft clay soil, even though I'm going to do my best to ram it down? The expense isn't an issue (it's not that pricey anyway), but I just want a bit of reassurance that I'm doing all that I can to stop the patio from sinking.
On top of that I will be mortaring the slabs one by one on a full bed of mortar (not the five dots in the corners/centre) to make it all as solid as possible. That one has been drilled into me by Tommy Walsh!
Last thing: the patio will end up being about 8m wide and 5.4m out into the garden. That seems to me like it's going to be catching a whole load of rainwater which will have to go somewhere. The somewhere in this case would be over the edge onto the garden.
While I will be sloping the patio away from the house, I'm not sure about the effect that amount of water will have on the grass below. I could make it slope sideways as well, but not sure if the neighbours will thank me for it! There are no drains to feed into in the garden, although there is one drain cover at the far side of the patio area - is this my most likely 'plug hole' and should I steer the water towards it?! My skills with the spirit level do not give me great confidence that I would be able to do this sucessfully without channeling water back towards the house!
An alternative would be to have a 'ditch' at the foot of the patio wall, filled with a fair amount of gravel/shingle, which could be used to soak away my mini-waterfall. I like the sound of that, actually - just thought of it as I was writing!
I'd appreciate any feedback you can give me on this. I don't mind 'over building', as I'd rather do more than I need in a week's work than suffer for years as it all sinks in and falls down! If it were up to me I'd be back-filling with concrete, not soil!
Cheers
Nick
PS Sorry for the essay, I just wanted to make sure I covered everything!