Unpaving

[DrPhill]

We have a new (to us) house. It has a lot of paving and we were thinking of removing some to create beds for flowers/vegetables/fruit. The paving is concrete slabs of mixed sizes (all edges multiples of a given distance so they fit together). We can think of two strategies

• Cut holes in paving, edge with low brick walls for a formal effect. I would need to get an expert to do this.....
• remove small areas of paving to create irregular shaped beds with no walls surrounding, for an informal effect.

Has anyone here tried either of these methods? How did it work? Are there any lessons for us to heed before we start?
With the second strategy would we need to 'stabilise' the edges somehow to stop the remaining slabs moving?

Thanks in advance
Phill

 

[Terry - Somerset]

We had a decayed old shed in the wrong place. It appeared (before demolition) to sit on a gravel bed - I assume good good for drainage.

When the old shed was removed I found slabs beneath. These had been laid on a compacted 4" concrete base. I have now removed the old slabs, partially replaced them with some spares to match the rest of the patio, and plan a raised bed over the rest.

A rather protracted tale - but your plan may hang on what lies below the existing paving - removing small areas then digging out the base to find fertile sold for replanting could be a lot of effort.

 

[Jacob]

It all depends on what's under the paving. - could be compacted hardcore. Perhaps have a trial go?
Have a similar problem with our new (to us) house where they laid out a sloping area with mini terraces of stepped paving, patches of gravel and little retaining walls. They then let it all grow over and we didn't know it was there until we removed a copse of Leylandii and other shrubs.
Now removing it all bit by bit.
Seems to be fashion around here for gravel, chippings, near 100% cover with just isolated plantings. A PITA and difficult to remove.

 

[DrPhill]

We had a decayed old shed in the wrong place. It appeared (before demolition) to sit on a gravel bed - I assume good good for drainage.

When the old shed was removed I found slabs beneath. These had been laid on a compacted 4" concrete base. I have now removed the old slabs, partially replaced them with some spares to match the rest of the patio, and plan a raised bed over the rest.

A rather protracted tale - but your plan may hang on what lies below the existing paving - removing small areas then digging out the base to find fertile sold for replanting could be a lot of effort.

Thanks Terry,
We think the slabs will be on a compacted gravel (chippings?) layer. Builder who excavated gravel traps around the house said it was on something proper (ie proper material) that had been compacted. 'Done right' was his opinion. Whatever 'right' is.
A raised bed is a possibility, but we would worry that nutrients will leach from the bed and encourage algae and moss to grow.

 

[DrPhill]

It all depends on what's under the paving. - could be compacted hardcore. Perhaps have a trial go?
Have a similar problem with our new (to us) house where they laid out a sloping area with mini terraces of stepped paving, patches of gravel and little retaining walls. They then let it all grow over and we didn't know it was there until we removed a copse of Leylandii and other shrubs.
Now removing it all bit by bit.
Seems to be fashion around here for gravel, chippings, near 100% cover with just isolated plantings. A PITA and difficult to remove.

Thanks Jacob, yes, 'what lies beneath' is the big question. Removing a slab might tell us, but the entire patio area is neat and tidy. My investigations would ruin that for sure.

A raised edge to the beds would allow soil to be built up over the existing base. The hole where the slab was plus 2 or 3 courses of brick would give a good enough depth for most of the plants that I would want to grow. Where something needed a deeper hole I would have to excavate. But I cannot lay bricks, so this would be a more costly answer.

 

[pidgeonpost]

Thanks Terry,
We think the slabs will be on a compacted gravel (chippings?) layer. Builder who excavated gravel traps around the house said it was on something proper (ie proper material) that had been compacted. 'Done right' was his opinion. Whatever 'right' is.
A raised bed is a possibility, but we would worry that nutrients will leach from the bed and encourage algae and moss

I guess that if you created some sort of raised bed you'd still need to remove some slabs and ensure your new bed will drain properly. If brickwork is not your thing maybe use timber? So-called 'sleepers' are a popular choice and will last a good while. Still hard work though.

 

[Tris]

Have a dig around the patio edges with a trowel, if the slabs are properly haunched with mortar then it's a fair bet they are either on a continuous bed over a 'hardcore' base, or possibly laid on dry mix over sub base then pointed. The first is a right pain to take up, the second not so bad. Drilling through the pointing between a couple of slabs you want to take up might help you find out too

 

[DrPhill]

Have a dig around the patio edges with a trowel, if the slabs are properly haunched with mortar then it's a fair bet they are either on a continuous bed over a 'hardcore' base, or possibly laid on dry mix over sub base then pointed. The first is a right pain to take up, the second not so bad. Drilling through the pointing between a couple of slabs you want to take up might help you find out too

Thanks Tris, the patio area is completely surrounded by walls, so digging around the edge may not be easy. Drilling through a gap may well be educational, I have a cheap SDS drill sitting idle.

 

[Richard_C]

There are lots of useful thoughts above about the slabs etc., but don't forget the soil beneath. Chances are it will be compacted, cold, no texture, no worms, maybe a giant ants nest, very likely impoverished. If the patio was laid at the time of building the house, it may well be a repository for broken bricks and all sorts. (someone local found a bent and rusty Honda moped under their patio). So think a bit about the biology, you might have to dig out and replace soil, it might take a year or two to recover. And think about aspect - what will grow there. It's not just a building question, it's a horticultural one. A few slabs removed and then semi raised beds gives you a bit more control and you can bring in some decent topsoil. Or maybe some very big pots and containers. As it's new to you, peer into neighbours gardens, what grows well and what have they done?

 

[Bingy man]

Having done many hard landscaping jobs over the years you will be surprised what folk hide ( especially builders) could be all good but could be a Pandora’s box. Anything from car engines to asbestos or drains to water mains. for example. If the existing slabs are in good condition then as one of the posts above go with raised beds . Square or round , octagonal or irregular the choice is yours . Position them in full sun or partial shade as per the growing requirements of what you’re growing . They will drain fine onto the existing slabs . Years ago a colleague asked me to help out on a turfing job , 1day prep raking and levelling and 1 day laying 160 sq meters of turf . Soon as the spade hit the earth-clang !! tried again a couple of feet away -clang !! It soon became evident that at some point house bricks had been laid as a cheap patio across the whole garden. In short - 3 weekends later and several skips we completed the 2 day job in 9 long days ( Fri sat sun ) some of the house bricks were buried 2 or 3 deep..

 

[DrPhill]

There are lots of useful thoughts above about the slabs etc., but don't forget the soil beneath. Chances are it will be compacted, cold, no texture, no worms, maybe a giant ants nest, very likely impoverished. If the patio was laid at the time of building the house, it may well be a repository for broken bricks and all sorts. (someone local found a bent and rusty Honda moped under their patio). So think a bit about the biology, you might have to dig out and replace soil, it might take a year or two to recover. And think about aspect - what will grow there. It's not just a building question, it's a horticultural one. A few slabs removed and then semi raised beds gives you a bit more control and you can bring in some decent topsoil. Or maybe some very big pots and containers. As it's new to you, peer into neighbours gardens, what grows well and what have they done?

You are right abut the soil. We are on or near clay here, but where we have dug it is a spit or more down. I am expecting poor soil and am mentally prepared to pay to build soil. I made a fruit tree area by laying cardboard on the lawn and covering it in wood chip. Using a similar principle the veg bed is mushroom compost over paper (over grass). Potatoes, onions, peas all doing fine.
I was instinctively drawn to the semi-raised bed for exactly the reasons that you mentioned. Most of the things that I will grow will cope with 8" of soil. A few trees will need bigger excavations, but even rubble (and hondas) will allow root growth.

As for aspect, the beds would be classified as 'sheltered sunny' or even 'very sheltered sunny' with one bed backed by the garage wall that faces almost directly south (apricot tree most likely going in there, plus low-growing herbs).

 

[DrPhill]

Having done many hard landscaping jobs over the years you will be surprised what folk hide ( especially builders) could be all good but could be a Pandora’s box. Anything from car engines to asbestos or drains to water mains. for example. If the existing slabs are in good condition then as one of the posts above go with raised beds . Square or round , octagonal or irregular the choice is yours . Position them in full sun or partial shade as per the growing requirements of what you’re growing . They will drain fine onto the existing slabs . Years ago a colleague asked me to help out on a turfing job , 1day prep raking and levelling and 1 day laying 160 sq meters of turf . Soon as the spade hit the earth-clang !! tried again a couple of feet away -clang !! It soon became evident that at some point house bricks had been laid as a cheap patio across the whole garden. In short - 3 weekends later and several skips we completed the 2 day job in 9 long days ( Fri sat sun ) some of the house bricks were buried 2 or 3 deep..

Indeed. It is this that worries me and makes me reluctant to follow the 'remove slabs and dig' option. Raising the soil certainly sounds the easiest way to go. I still like the idea of removing slabs - the patio does not have enough slope and so grows moss and algae during the winter. Removing slabs for beds might reduce this problem by adding drainage. Building beds on top of slabs may result in nutrient leaching out to feed the moss and algae.

My guess is that 'sleepers' would be more cost-effective edging, and give a softer, less formal effect. That gives a potential 8" of soil plus whatever breaks easily from the layer under the slabs.

 

[John Hall]

As already mentioned a lot depends on what is under the pavers..if it’s sand, removing individual pavers then leaves the edges of the remaining around the space created unsupported and liable to sink..until you’ve taken one up you won’t know what issues you have..

 

[Bingy man]

Indeed. It is this that worries me and makes me reluctant to follow the 'remove slabs and dig' option. Raising the soil certainly sounds the easiest way to go. I still like the idea of removing slabs - the patio does not have enough slope and so grows moss and algae during the winter. Removing slabs for beds might reduce this problem by adding drainage. Building beds on top of slabs may result in nutrient leaching out to feed the moss and algae.

My guess is that 'sleepers' would be more cost-effective edging, and give a softer, less formal effect. That gives a potential 8" of soil plus whatever breaks easily from the layer under the slabs.

You could always stack 2 or 3 sleepers high and fill the 1st 8 “ with gravel or similar. Moss and Algae will grow regardless especially if there is lying water . Treat it with a spray or jetwash on a regular basis. It’s difficult lifting the slabs as above you can potentially disturb others . You might hit a sweet spot with good soil but the next one you lift could be a brick pit or similar ..again they could be laid on a dry bed of sand / or laid on the dreaded blobs 1 each corner and 1 in the middle,, or they could be sand /cement on a solid concrete base. Think if you are going to remove slabs then lift one at the front or back of patio ( one or two that are easy to get up ) and see what your up against..

 

[DrPhill]

You could always stack 2 or 3 sleepers high and fill the 1st 8 “ with gravel or similar. Moss and Algae will grow regardless especially if there is lying water . Treat it with a spray or jetwash on a regular basis. It’s difficult lifting the slabs as above you can potentially disturb others . You might hit a sweet spot with good soil but the next one you lift could be a brick pit or similar ..again they could be laid on a dry bed of sand / or laid on the dreaded blobs 1 each corner and 1 in the middle,, or they could be sand /cement on a solid concrete base. Think if you are going to remove slabs then lift one at the front or back of patio ( one or two that are easy to get up ) and see what your up against..

Thanks for the advice. I have ordered a long SDS drill bit and plan to drill some holes through the mortar between some slabs. This might give me some more information with minimum destruction.

 

[Bingy man]

Thanks for the advice. I have ordered a long SDS drill bit and plan to drill some holes through the mortar between some slabs. This might give me some more information with minimum destruction.

Not a bad idea

 

[HOJ]

I have ordered a long SDS drill bit and plan to drill some holes through the mortar between some slabs.

Are you confident there are no services that may run underneath or drainage, foul and rainwater etc..

Just thought worth a mention as my pal was fitting some timber edging for a gravel path, banged a wooden stake straight through his plastic sewer pipe, didn't realise for a couple of weeks when they started to have problems with flushing...

 

[DrPhill]

Not a bad idea

Yep, it was suggested above!

 

[DrPhill]

Are you confident there are no services that may run underneath or drainage, foul and rainwater etc..

Just thought worth a mention as my pal was fitting some timber edging for a gravel path, banged a wooden stake straight through his plastic sewer pipe, didn't realise for a couple of weeks when they started to have problems with flushing...

Thanks for the thought - I'm pretty confident - drains, sewer, electric and gas all come in from the front of the property. Nothing on the searches at the back. Some electrics to/from the garage but I can avoid the obvious routes.

 

[TomGW]

Going back to your initial post and the suggested option of the more formal, raised brick beds. Don't rule out this option and consider dry walling as a diy solution. These are specifically designed for retaining. This would avoid a massive amount of heavy work excavating hardcore, clay etc.
https://www.wickes.co.uk/Products/G.../Paving+Walling/Walling+Wall-Bricks/c/1000716