Advice needed for patio subbase

28 Jan 2023
Reaction score
United Kingdom
I've read and re-read a lot of threads about patio subbases but still can't decide how to proceed with mine.

Late last year I dug out an area 50sq.m down roughly 160mm from finished surface level. Working to the 100mm type 1/ 40mm bed / 20 porcelain tile advice that seems quite common. The ground was firm.

After a break over Christmas I started up again this week but a thick frost had got into the top 50mm of the soil and my digging to level it off turn the surface into a mush. I used a thin layer of the type 1 and the wacker plate in an attempt to firm it up but what I'm left with in places has a plasticine quality to it. If I press my heel into it it spreads and leaves an impression. The soil didn't seem to be clay but I guess it's as good as.

I've got groundtex membrane to go down next and then the 100mm of type 1 but I cannot decide if this ground can be considered "firm". It doesn't seem likely it will dry out in the few days I have before I need to use the wacker I've hired.

Should I proceed or am I likely to have problems in the future?

Any advice would be greatly appreciated! I want to do a good job but have a tendency to overthink these things and no experience to draw on.
Sponsored Links
The only thing I’m aware of if it goes spongey is to wait for it to dry out a bit. 50m2 of porcelain isn’t going to be forgiving either if this bit’s not done right. At least whackers aren’t mega money to hire (again). Others may have different opinions…
I appreciate your thoughts. I did a lot of research before starting this project but spongy/plasticy soil was not something I anticipated and it's thrown me a bit. My instinct says to scrape it down to something more solid but I don't want to create more work and expense for myself if it's a non-issue.
I'm not a pro but I did our patio and driveway.
As far as I know as long as it's not swimming, the whole point of the hard core is to spread the load. As long as you get the proper thickness, the damp soil won't have any concentrated load.
We had a few wet areas and a few areas that were quite firm and there hasn't been an issue so far.
Sponsored Links
Thanks John. This also makes sense. The surface, in places, is simply spreading, not sinking, when I walk on it. It's like a half inch of paste on top of a harder surface. Seems like you had a similar situation so it's reassuring to hear you've had no issues.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local