Remedial advice for new patio sought please - 450x450 slabs, split level garden

[Helsbels]

Hello everyone

I joined last night and am pleased to find such a great website.

Please can anyone offer any advice on remedial work for a patio that was done from scratch less than 12 months ago? Unfortunately I employed a generalist builder to do my Mum’s garden. Luckily I’ve found this website!! I need to employ a landscape garden/patio expert to remedial work, but this time I want to know what should be done exactly so that the techniques, materials and quantities used are correct and to a high standard. This time I would like the job to be detailed in a contract before the work starts to avoid further problems.

Description of patio:
- Patio size circa 38 sqm with Bradstone utility paving slabs 450 x 450. Its about 30foot long and 12 foot wide. A terraced house.
- split on 2 levels as the garden is on a slope, with a retaining wall and a step to lower level. The retaining wall and step has London Bricks facing out with a patio slab on top.
- The patio has
-black plastic Damp Proof plastic under the whole surface of the patio (he told me he was putting down a membrane to stop weeds growing up through patio)
- then ballast
- then sharp sand
- the slabs and some type of dry sand without any cement, in between the slabs.
- He built a step one London brick high - on top of the patio meeting the French doors of the house, the full width of the French doors. The step was butted to the house bricks and filled with ballast. When the new French doors were fitted the window fitter pointed out that the step was acting like a sponge and had soaked the house bricks. The pointing of the house bricks had crumbled away so the bricks were loose and a couple had cracked, a little damp inside the house on the skirting board. There had never been any problems with damp externally or internally ever before. We took the step away from the house.
- Unfortunately the patio finishes less 150mm from the DPC
- At the bottom of the garden, the patio finishes circa 100mm from a very old wall and is filled with slate chippings – this is supposed to be a ‘French’ drain

Despite the hot summer last year the slabs didn’t dry out – they there wet around the edges with a round dry patch in middle. But now this year they do finally seem to have dried out across the surface of each slab now its sunnier and the green on the slabs is going where its in the sun. I’m not sure why! The ‘sand’ type material in between the slabs has all gone green and looks like it could all turn into moss. The slabs have totally discoloured.

-The soil in the garden has some clay content.

The only good point is – all patio slabs are all level i.e. wherever you place a chair, the chair doesn’t rock at all.

Can any one please offer suggestions as to the correct remedial works?

What do people think of the following suggested remedial works?:

-cut patio back from the house bricks (as too close to house DPC) Horizontally - 150mm gap between house bricks and patio slabs? Vertically – 300mm from house DPC and then filled with slate chippings so that chippings finish 150 mm below house DPC? Should there be a retaining wall directly under the edge of the patio to keep the earth next the house in an upright position to stop crumbling into the ‘trench’?

-cut patio back from the wall at the bottom of the garden (to improve drainage) Should be 600mm from the wall? What should be dug/ done in the drain area?

-cut back patio from the 2 parallel sides running the length of the garden (so that if fence posts need to be replaced, the patio would be undisturbed) What distance?

- replace the current sand type mixture between the patio slabs with wet mortar pointing 1:3 cement sand (to make waterproof, to stop water penetrating vertically through the patio as it currently does)

- repair/replace/rectify the drain next to the house which handles has the roof gutter rainwater for this house and the 2 either side. Previously the gutter pipe finished inside the drain so there wasn’t the chance of any splashing up against the house as it does currently. Not sure best way to do this.

- perhaps - replace the retaining wall and the step leading down to the lower level. Maybe this does or doesn't need to be replaced? I don’t think he used any vertical damp proof. He put some weep holes using some plastic pipe I had left over from when my Mum had some plumbing work done, not the 3 /4 tubing pipe. I’m worried that the wall might blow and crack after some cold weather. Also, its green and looks like moss will be covering it soon. I’m guessing he filled the step with ballast material the same way he did for the house step he built, and so created a ‘sponge’ next to the retaining wall.

-At the bottom of the garden, the patio is too close to the 80yr old wall at the bottom of the garden ie the patio is 30mm from this wall. To increase the drainage, what distance should the patio be from this wall? 600mm? What prep work should be done to this space? and should it finish be lower than the patio? Just slate chippings ok?

What distance should the patio be from the fences that run the full length parallel to the patio? What is recommended so that the patio would not need to be disturbed if the fence posts need to be replaced? 150mm?

I would like to replace the current sand pointing with mortar pointing –
is 1 cement: 3 sand okay? Should the pointing be smooth or with a ridge?

Should the patio be damped with water before pointing to avoid the slabs sucking up the moisture form the mortar and weakening the mortar and avoid the picture frame effect? Because of the 'PDC plastic' under the patio, I was thinking maybe better to do pointing when its dry to avoid trapping excess water between the patio and the plastic?

I’m sorry for the very long email. I’d be very grateful for any help!
Thank you in advance
Helsbels

[cookiewales]

hi have sent you a pm am up in north london soon can call and look cheers cookie

[Helsbels]

Hi Cookie
Thanks for the personal message. I'll email you some photos to give you a better idea of the patio.
Cheers
Helsbels

[Helsbels]

Hello everyone

I had a good chat on the phone with Cookie on Monday evening about his ideas for remedial works and he suggested I put up the photos for everyone to see. Would anyone else like to make any comments or suggestions about their ideas for remedial works at all?

Cookie suggested:
Overall – done an ok job but cut corners on materials and how used them ie utility slabs aren’t the best quality plus DPC material shouldn’t be under a patio. Pulling everything up and starting again isn’t necessary as remedial works will be fine, especially as no budget to do from scratch.

Here is a link to photos:
http://www.facebook.com/album.p....89f0c48

- no need to cut patio away from house - as 5inches below from house DPC rather than 6inches and as patio runs away from the house, more than likely wont be a problem, although could put a sealant running between patio and house bricks. A drainage channel between house and patio isn’t really necessary.
Remove bricks that was the step clean down patio and treat with Algeran twice a year keeps of green moss when no sun gets on patio.

I have added a new close up photo of the damp proof material poking up from the patio next to the house bricks. Cookie hasn’t seen this photo so I don’t know if with this extra info he would suggest cutting patio away from house or not.


- the drain next to the house needs a 45 degree elbow, put a shoe on the bottom of black pipe so runs into the gully, the end of the black pipe will finish slightly above the drain hole, add a sleeve.

- no need to cut patio away from the fencing running parallel both sides of the garden as okay drainage. I forgot to ask Cookie – what would happen to slabs if fence posts need replacing? Would it be beneficial to cut the slabs back a bit for this reason?

-the retaining wall and step is ok to leave as it is even though no vertical DPC and only 1 skin. The wrong bricks have been used - should have been built with engineering bricks. The ones used are Funton F2 bricks with 21% water absorbency. Should still last some years.

- The slab directly above the retaining wall was removed with a chisel by a guy who visited to do a quote that I found on the Marshall’s registered installer list. This slab is now loose, as seen in the photo. Cookie suggested apply SBR on back of loose slab and put back on using wet mortar mix 1:4.

-‘French drain’ at the bottom of the garden – patio slabs 3cm away from the old wall, not 10cm I mentioned to Cookie. What distance should patio be from the very old wall? The patio is a bit higher than the gardens either side.

- replace all the pointing for the patio with 1:4 wet mortar mix with some SBR mixed in. Should take 2 days to redo pointing. What is probably there, is a builders sand for the ‘pointing’

Maybe you agree with Cookie or have other ideas? Hopefully, this is an interesting scenario on this great website.

I look forward to hearing from you.

Cheers
Helsbels
PS apologies for so many questions

[cookiewales]

just seen the extra pictures a good clean would make a big difference remedial work should not cost that much refit loose slabs take out duff pointing use romex dran to repoint what do the rest of you boys think ps forget the questions just look at the pictures

[Helsbels]

Hi everyone

Thanks for the post Cookie. Glad you’ve seen the new photos!!!

Would a waterproof material for new jointing like a 1:4 wet mortar mix with some SBR mixed in or Easipoint standard applied by gun injection be better than the Romex which is water permeable?

Unfortunately there is a DPC plastic material under the sand/ballast bedding layer. It traps any water passing through the jointing within the bedding layer. If the new jointing material is water permeable then the bedding will be more and more saturated and likely to grow black mould? Should this DPC plastic have some holes drilled into it between the joints before re-pointing?
Cheers
Helbels

[lutonlagerlout]

i concur with the cookiemonster
overall its a fair job
silly things like no shoe on the downpipe and weepholes on the top step?
but no big dramas there
rake out joints ,hoover out joints,repoint with easipoint or romex/gftk
give it a good clean a week later and bobs your uncle
LLL

[Helsbels]

Thanks for your input LLL

Can I just double check please? So, don't worry about cutting patio away from the house or increasing the drainage area at bottom of the garden?
Cheers
Helsbels

[cookiewales]

Thanks for your input LLL

Can I just double check please? So, don't worry about cutting patio away from the house or increasing the drainage area at bottom of the garden?
Cheers
Helsbels

there is no point doing that by the house your not gaining anything by doing it only wasting money the bottom could be the same ps the amount of plants and depth of dig to drink all that water wont happen because your 10 inches higher than adjoining gardens your water is going there way give it a good clean that will make it look better straight away and give you a idea what the water is doing cheers cookie :;): :;): ps post up points that the contractor who came to give you a price :;):

[Helsbels]

Morning all

I've checked with my Mum and she thinks that the maximum the garden has been built up is up to 3 inches, rather than up to 10inches higher than the neighbours either side.

The feedback from a local contractor for remedial work -
1)put french drain/soakaway type thing at bottom of garden ie:
ie cut patio away form very old wall, dig out between patio and wall. A concrete triangle angled away from last slab to provide upright support for patio. Drain running in the 'tough' that’s created. Fill with 1)rocky type stones 2)then shingle 3)then earth. Plant some plants so they can also take water up and away.

2) where patio meets house – cut slabs away from house, dig out, support edging of patio with some concrete, add shingle/slating chippings finishing 150mm below DPC

3) take out and re-point

4) sort drain by house

Thanks
Helsbels

[cookiewales]

Morning all

I've checked with my Mum and she thinks that the maximum the garden has been built up is up to 3 inches, rather than up to 10inches higher than the neighbours either side.

The feedback from a local contractor for remedial work -
1)put french drain/soakaway type thing at bottom of garden ie:
ie cut patio away form very old wall, dig out between patio and wall. A concrete triangle angled away from last slab to provide upright support for patio. Drain running in the 'tough' that’s created. Fill with 1)rocky type stones 2)then shingle 3)then earth. Plant some plants so they can also take water up and away.

2) where patio meets house – cut slabs away from house, dig out, support edging of patio with some concrete, add shingle/slating chippings finishing 150mm below DPC

3) take out and re-point

4) sort drain by house

Thanks
Helsbels

hi if you look at your pictures he has put gravel boards along each side these are 12 inches deep and you can see next doors garden is lower :;): :;):

[Helsbels]

I've just picked away at the slate chippings by the gravel board -they 6 inches deep. How does that affect things?
Cheers
Helsbels

[Helsbels]

Thanks for your post Cookie, I see what you mean now about not needing to do any cutting away or anything at the top or bottom of patio.

I’ve put water on patio – it runs down away from the house and out to the sides off the slabs and also straight down into the jointing.

I’m just still confused about what material to use for the pointing though.

LLL you kindly suggested either easipoint (non-water permeable) or romex/gftk (water permeable) for the new pointing.

And cookie kindly suggested romex drain (water permeable).

Is the choice of either water permeable or non- water permeable material for the new pointing quite critical?

If water permeable then drill some holes into the DPC plastic in between paving joints. if non-water permeable ie easipoint/wet mortar then leave the PDC plastic as it is?

Sorry to persist with all these questions, especially if they’ve been answered but its just me not understanding your replies! Thankyou for your patience.

also I’ve found some interesting photos documenting the building of this ‘unconventional’ patio:
http://www.facebook.com/album.p....b99a88c

I wish I had read all the pages here and bought Tony's book before embarking on a new patio!!!
cheers
helsbels

[cookiewales]

well they are better pictures standard of laying slabs very good fence very good bottom base ie dads old good rest of base is sand that's why dpc has been laid so do not puncture it for the amount of water that will run into joints when re pointed with sand and cement or easypoint wont cause any problems easy point does not stain or d2000 romex ps as i said before your neighbour's are having your water( if its not broke don't fix it )your jobs not that bad there are a lot worse out there :;): ???

[Helsbels]

Thanks for your feedback on the photos of patio being constructed and your advice Cookie.

okay so no puncturing of plastic DPC Now to decide on what material for pointing. I'll re-read the excellent pages on this site!!

thanks again