Flagging (paving slabs) onto damp/soft ground...?

JustAnotherSaver

We bought a house which later on we found there was an issue regards water running under the house. I don't mean a river but there's water. I don't really want to spend too much time going into the ins & outs of it but it affects about 4 houses in the cul-de-sac with the direction this water takes. Some are affected differently. For example it ruined our living room - damp walls, salty plaster, water under the floorboards. The house at the immediate rear of us - the next street, their house is fine but their garden is incredibly boggy. The house next to us has a boggy garden and had a bad living room before damp proofing.

We've been told our garden was done out with hardcore (it does seem raised up) and then paved over. There was a small grass area and this soil is very clay like. Very damp.

We bought the house late 2013. I can't be sure but i think the flags are not as level as they once were. Some flags i'm fairly sure have sunk a little compared to what they were when we bought the house. At any rate i hope they have sunk since they were laid because if that's how they were on day 1 then it's a terrible job.

One thing i do know for sure though is the cement between them has disappeared on many of the flags. On some it's still there but on many it's disappeared.

The hearth inside is also damp. They had to re-do the (natural stone) flags we had put down and put DPC down first. Nevertheless, it's still cracked the joints although this time it hasn't physically popped one of the flags off, just cracked the joints.


So i'm wondering does a damp ground guarantee cracking the cement joints on the flags in the back garden?
Is there a workaround (if the answer is stop the water then no there's no workaround)?

Somewhere down the line i'd like to replace the horrible flags we have for indian stone natural flags but i don't want to shell out big amounts only for it to be done poorly & miss something important regards this damp ground.

garrysibbald

From what you say I would be more concerned about the damp within the house, but regarding the paito; It sounds like your patio has been laid using a "dot and dab" method for the cement. The ground subsquently moves an/or sinks and you start to develop uneveness. The only way I would reccommend a patiio to be layed is using a bed of mortar over a hard core base. The slabs are seated within the bed of mortar which eliminates the chance of any movement and the ground being washed away from beneath the slabs.

You must ensure that the patio stays below the house damp proof course (at least 150mm below) to avoid the chance of damp from the patio breaching the damp proof course.
It would be worth checking that this isn't the reason for damp in the house at the moment!

JustAnotherSaver

I'm not sure how the patio is in line with the DPC but i know it runs up to the air bricks at the back.

Regards the cause of damp it's not the back garden/patio that's the cause. Talking to neighbours it's been a problem since the beginning of time, before the back garden was even altered. Thankfully our immediate neighbour has lived here for 200 years so has given us a very interesting run down of the history. She would remember peoples feet sinking in the grass, chairs disappearing as you sat in them on the grass (there's no grass any more).

The cause is a stream/brook/some sort of water that runs under the house. It affects about 4 houses in the middle of the street which is in a bit of a dip as well as houses to the rear, all affected in different ways (our living room was very damp before we had it ripped out and tanked), next door was similar, the house at the rear has no such problem in his house but because of the bend of it it made his garden a total bogland so he had to create decking.



Funny you say about unevenness because it's been recent that i've asked my wife about a few paving slabs and whether they were always dipped like that as i'm sure some were flush with the flag next to them whereas one is now dipped (and as said the joints have pretty much disappeared on most).


When we have the money ideally i want to get indian paving slabs down but at £17/m2 while i'm an idiot when it comes to DIY i want to know what the guy SHOULD be doing so that i can at least talk to him about it and get vibes off those giving quotes.