Resurfacing yard

[ClaudiusTheIdiot]

I'm trying to improve the yard outside the back door (link to photo is below). It's surfaced with concrete, slate flags, and some gravel-filled trenches that contain new rainwater pipes. I want to leave in place most of the concrete as there are older drains protected by it. I can remove the slate flags (which are irregular and somewhat broken) and want to cover the gravel-filled trenches. The area goes up to the house wall, which is cement rendered. The wall is of rubble stone construction so has no damp proof course. The ground slopes along and away from the house wall, about 30mm per metre (ie down to the left and towards the camera). I want the level next to the wall to be no higher than at present, to avoid damp. I can cut away the concrete near the wall.

I thought to cover the area with concrete, but it couldn't be as thick as would normally be used because of the existing concrete and the need to maintain a slope away from the house. The nearest concrete that I need to leave undisturbed is about 2m from the corner of the house (centre right of photo). It could be covered with say 30mm of new concrete while maintaining a slope. Will this be thick enough to avoid fragmentation? Over some of the area the ground would be lower so the concrete thicker.

I also thought to cut grooves in the new concrete to simulate flags. If it cracks it should be along the grooves, and they would be grouted in any case for appearances and to avoid weed growth.
I'll leave the cobbles in place.

Thank you for any views on this, or suggestions for other methods.

Photo is at https://www.flickr.com/photos/70085366@N04/

[AsleepInYorkshire]

I'm trying to improve the yard outside the back door (link to photo is below). It's surfaced with concrete, slate flags, and some gravel-filled trenches that contain new rainwater pipes. I want to leave in place most of the concrete as there are older drains protected by it. I can remove the slate flags (which are irregular and somewhat broken) and want to cover the gravel-filled trenches. The area goes up to the house wall, which is cement rendered. The wall is of rubble stone construction so has no damp proof course. The ground slopes along and away from the house wall, about 30mm per metre (ie down to the left and towards the camera). I want the level next to the wall to be no higher than at present, to avoid damp. I can cut away the concrete near the wall.

I thought to cover the area with concrete, but it couldn't be as thick as would normally be used because of the existing concrete and the need to maintain a slope away from the house. The nearest concrete that I need to leave undisturbed is about 2m from the corner of the house (centre right of photo). It could be covered with say 30mm of new concrete while maintaining a slope. Will this be thick enough to avoid fragmentation? Over some of the area the ground would be lower so the concrete thicker.

I also thought to cut grooves in the new concrete to simulate flags. If it cracks it should be along the grooves, and they would be grouted in any case for appearances and to avoid weed growth.
I'll leave the cobbles in place.

Thank you for any views on this, or suggestions for other methods.

Photo is at https://www.flickr.com/photos/70085366@N04/

There are two types of concrete. The first is un-cracked. The second is "waiting to crack".

Regrettably 30mm depth of concrete will successfully be in the second category quite quickly. And laying concrete over concrete will create "hard spots" that will intensify the need to crack.

There are no short cuts with concrete I'm afraid. It's a very unforgiving material. I think you are describing a cob wall as the external wall construction. These are notoriously difficult to keep dry. I'd suggest you think seriously about laying any concrete near these, even if it doesn't breach existing finished levels. Gravel does allow surface water to drain. At the very least I'd suggest a 100mm wide gravel margin between the existing wall and new concrete. I'd also suggest you use precast concrete slabs which, if you shop around you should be able to buy a reduced thickness. However, ultimately they should be laid on a sand bed and that would mean removing some of the exisitng concrete.

On those occasions when I have tried to cut corners with concrete it has always fallen into the "cracked category".

AiY

[sg31]

I agree with AIY concrete is not suitable for the situation you describe.

I would be tempted to leave the existing concrete in situ uncovered and remove the flags and any other bits you don't like and replace with some sort of gravel. You could use a compacted gravel to leave a hard surface that doesn't move, something like..

https://www.allgreengroup.co.uk/prod/se ... ath-gravel.

I don't know the company I linked to, I've never used them. I have seen the Somerset gold and am seriously considering it for my own property.

Good luck with the project. Please let us know what you finally decide.

[redsturgeon]

Sorry I had used my moderator edit button instead of the quote button in my reply to you earlier.
Here is my response:

Really your concrete should be about 100mm thick to provide a lasting sound patio.

You should get the existing surfaces broken up, you can then use the rubble together with extra scalpings as a sub base for the final concrete layer,
properly compacted.

John

[ClaudiusTheIdiot]

Thank you for suggestions all

Is there a good way to clean up the parts that are old concrete? Something that would remove a surface layer. Pressure washing doesn't seem quite enough, and I don't think I could get an even finish with an angle grinder. Is there anything else?

[sg31]

Hydrochloric acid also known as muriatic acid is often used. It is known as brick cleaner and is readily available online and at builders merchants. It is obviously a strong acid and you need to use protection because it burns like hell if you get it on your skin. In effect it eats away at the surface of the concrete. I'd advise trying it on a small area first.

Have a google for 'cleaning concrete' and you should find something online detailing how to get best results.

Be careful.

[AsleepInYorkshire]

Thank you for suggestions all

Is there a good way to clean up the parts that are old concrete? Something that would remove a surface layer. Pressure washing doesn't seem quite enough, and I don't think I could get an even finish with an angle grinder. Is there anything else?

1. Brick acid
2. Jeyes Fluid
3. Soda crystals.
4. Concrete floor sander (very expensive and looks as if it may do more damage than good)

There are jointing compounds on the market which you could use to fill the gaps (cracks) in the concrete. But you would have to saw them out and - yada yada yada - lots of work, lots of expense and very little to see at the end.

I've looked at your photograph and I would advise against brick acid. It will cost time and also expose you to some risk (it being an acid) with very little to show at the end except a bit more cleaner concrete. I'd plump for regular use of Jeyes Fluid.

Jeyes will reduce weed growth as it sterilises the ground in which weeds grow (the instructions say to wash it off after application - I don't bother with that bit )

I don't think you've many options that don't involve a lot of excavation and cost other than to control the weeds and keep moss off the concrete.

AiY

[ClaudiusTheIdiot]

For the present (and I hope not to redo it) I've removed some gravel from the trenches and topped them up with concrete typcally 70mm+ thick, though less in places. The existing concrete remains, but with the cracks grouted. The slate flags that were moved have been relaid on gravel, with grouting between them. I've also grouted between the cobbles so they don't need weeding.

Most of the concrete was 1+2+3 cement + sand + gravel or chippings. Grouting was 1+3, with black colouring in the grout between the slate flags. Mostly sharp sand, with some soft sand - it didn't seem much different to apply. I tried two concrete cleaners, hydrochloric acid 10% to 20%, and alkyl dimethyl benzyl ammonium chloride, on small areas. Then washed and wire brushed. The cleaners didn't appear to make any difference in the end, but they seem to have been harmless - the washings went into the grass without any visible damage. The wire brushing did make some improvement.

I tried a few wire brushes, most from two of the cut price diy chains. The best I thought was quite large, 150mm dia x 20mm thick with a selection of plastic centres so you need a separate mandrel. I broke a few centres but managed to adapt the mandrel for different centres. There were also some cheaper ones, 100mm dia with a shaft already attached. One of the smaller brushes cleaned 7 sq m, and the large one has plenty of use left after 11 sq m of concrete and a larger area of cobbles. I used a fairly large drill with a second handle near the chuck, and found it quite heavy work, especially with the larger brush.

I also tried some knotted steel brushes in an angle grinder. They worked ok but were a bit fierce on the concrete (and on me). If you use a high speed tool like this check the speed rating of the brush.

I didn't want to try lifting the existing concrete because of the old drains, so the job is functional if not beautiful. There are fewer places for the slugs to hide - not sure whether that's good or not. Thanks again to all for advice.

[Mike88]

Laying concrete without expansion joints is a waste of time as cracks will appear. I would be tempted to pave over the existing surface.

[Sobraon]

I am currently on a break from re-surfacing our kitchen yard. If its good enough for the council its good enough for me so I am using council slabs . Mind you they are blooming heavy on your own at over 63kg each. Still onwards...