We had a new patio built just over 2 years ago following completion of an extension.
Its approx. 15m wide and about 4.5m deep, and is raised approx. 40cm above the garden level. We live in SE London - soil in the area is clay.
Over the past 12 months I've notice movement in the patio via gaps appearing between the grout and porcelain slabs. I've run a string line across the very front of it and there is a dip of approx. 30mm in the centre of it, which reduces towards the sides. This is more pronounced across the first 2 rows of slabs.
I recall the builder digging a trench for footings - probably around 60cm deep, which was then filled with hardcore before be poured a concrete supporting "wall" over this, from ground level I think. The base was a mix of hardcore and rubble from the building work, some MOT, and in some places a pre existing patio that was built over.
The slabs were laid dot & dab directly onto the compacted hardcore. He said at the time this was to allow for ground movement as there is a large oak tree at the front right corner of the patio. Several of the slabs have become loose underfoot in the past 18m, but I'm more concerned about the dip and forward movement of the first 2 rows of slabs.
Would be great to have some thoughts on suggested fixes. I've attached some photos.
Its approx. 15m wide and about 4.5m deep, and is raised approx. 40cm above the garden level. We live in SE London - soil in the area is clay.
Over the past 12 months I've notice movement in the patio via gaps appearing between the grout and porcelain slabs. I've run a string line across the very front of it and there is a dip of approx. 30mm in the centre of it, which reduces towards the sides. This is more pronounced across the first 2 rows of slabs.
I recall the builder digging a trench for footings - probably around 60cm deep, which was then filled with hardcore before be poured a concrete supporting "wall" over this, from ground level I think. The base was a mix of hardcore and rubble from the building work, some MOT, and in some places a pre existing patio that was built over.
The slabs were laid dot & dab directly onto the compacted hardcore. He said at the time this was to allow for ground movement as there is a large oak tree at the front right corner of the patio. Several of the slabs have become loose underfoot in the past 18m, but I'm more concerned about the dip and forward movement of the first 2 rows of slabs.
Would be great to have some thoughts on suggested fixes. I've attached some photos.
