Advice on porcelain laying

Hi, if the grass area you are laying over is low to other surfaces- lower than the drive for example- there would be no need to dig out soil. As long as your finished patio is 150mm lower than the house damp course (if it butt's up to the house) there would be no need to dig out. These circumstances are possible, but unusual, it almost always the case that digging is required. As to the mot1 base: the best base for all slabs- pink concrete to high end porcelain is 100mm cast concrete, second best is 100mm THOUGHROUGHLY compacted mot1 or 50mm to dust or ballast. Membrane is needed for whackered bases to prevent mixing with the subbase. 50mm of mot 1 is definitely not enough. 50mm of cast concrete would not be enough. I'm not sure what you mean by 'laying on top of existing stone' - is this a previous patio, or do you mean gravel? You might get away with overlaying existing slabs, but it's dodgy, loose gravel is no kind of base at all. I'd recommend digging out 150mm below finished level, laying in any old slabs as core, casting the base - or whackering 100mm mot1- and laying your porcelain on a full bed of mortar 25mm thick, no less than 6:1 mix, with a bridging slurry on the slab back. Basically, a quick cheap base is a false economy- once the slabs are glued to the mortar there'll be no cleaning it off. If your base fails, everything on top will go to the skip and you'll be starting again. Do it right, do it once!

Hi, the process should go , hard soil which is the area dug out for the patio area. “ which means the top soil should be removed” top soil is loose and compresses under weight building anything on top soli will inevitably fail. Then the membrane should be laid to stop the type one transitioning through into the soil over time,. With porcelain tiles they should be laid on a bed of cement/mortar… NOT sand & need the correct grout you shouldn't fill the gaps with Killeen dried sand.

Definitely not the way to do it

Porcelain paving is very unforgiving so the groundworks matter a lot. What you’re describing is basically a stack of shortcuts that can look fine short-term and then fail later down the line. Dig out, compact, then membrane, 100mm type 1 for patio for the sub-base

From a professional point of view, some of the methods described are not best practice for porcelain paving and could cause problems in the future. Porcelain slabs need a solid, well-prepared sub-base because they are less forgiving than standard concrete slabs. Normally, topsoil should be fully removed and replaced with a properly compacted MOT Type 1 sub-base of around 100mm (depending on ground conditions). Reducing this to 50mm can increase the risk of movement and sinking over time. Laying porcelain directly on existing stone or shortcuts in the build-up may save time initially, but it can compromise drainage and long-term stability. A membrane is usually installed to prevent weed growth and contamination of the sub-base, but sand layers under membranes are not typically part of a standard porcelain patio specification. Best practice is: excavate to suitable depth → compacted Type 1 sub-base → mortar bed (with full coverage) → primed porcelain slab. This ensures strength, drainage, and durability. If you are unsure or uncomfortable with the proposed method, it is reasonable to ask the installer to explain their process in detail or seek a second opinion. A properly installed porcelain patio should last many years without movement or failure.

Completely wrong information given by contractors hopefully you worked it out for yourself and got a proper contractor in

You’re not overreacting. What you’re describing isn’t just “a different method” it’s a stack of shortcuts that might look fine for a year or two and then start failing. Porcelain is unforgiving, and groundwork is where most problems begin. Porcelain slabs need a stable, non-organic sub-base. Leaving topsoil underneath is one of the most common causes of: sinking,rocking slabs,cracked grout,water pooling Putting sand under the membrane: defeats the purpose of the membrane introduces a layer that can shift or wash out suggests they’re trying to “make it level” instead of excavating properly Sand is for block paving, not porcelain bases.

It needs stripping out and doing properly with type 1 compacted and slurry back of slabs and lay on sand and cement

The proper war to lay porcelain is to dig out 150mm this allows 100mm for type 1 sub base approx 30mm for wet bed and 20mm for porcelain tile. the most important prep when laying this type of material is to coat each tile with adhesive prior to laying, this allows the tile to adhere to the bed. a full bed of cement is required (not spotting). whenever i lay porcelain i use a 7mm spacer between each tile, never butt joint they will chip the edges and then i use a brush in pointing compound to finish. I hope this has been helpful.

When it comes to laying porcelain, there are definitely best practices that ensure a long-lasting and beautiful result. Some of the things you've described do sound a little... unconventional, like skipping the topsoil removal and putting porcelain directly on top of existing stone without proper preparation. That might save time in the short run, but it could lead to problems down the road, like uneven settling or cracking. And the detail about the sand under the membrane is a bit head-scratching 😂