ᐅ Slate tiles on the terrace are loose – how to glue and grout them

Hello – as you can see in the pictures, my terrace has become a bit worn. However, I don’t want to have the entire terrace redone, just the damaged sections repaired. Here is my plan:

- Remove all loose slabs and clean them, especially the underside
- Chisel out any deteriorated joints as much as possible
- Reattach the loose slabs using construction adhesive or silicone
- Fill the open joints with joint mortar

A few questions:

- Do you think the adhesive or silicone will hold on the substrate (concrete foundation) and the slabs?
- Which is better, construction adhesive or silicone?
- What kind of joint mortar should be used for this?

Thanks in advance – Regards, Manuel

Why not use tile adhesive? Good quality ones are also suitable for natural stone and outdoor use. That would seem like the obvious choice to me.

Today, I lifted the slabs and I really don’t like how it looks underneath. It’s quite hard, partly concrete or mortar, but especially around the edges there’s a lot of soil (see photos). What a mess…

Here’s the problem. It’s a rental property, and the landlord only wants a quick fix, so a company should just glue the few loose slabs down. Two companies inspected it and declined, saying it needs to be done properly. But the landlord doesn’t want that because it’s too expensive. So I thought, OK, I’ll glue them myself, and even if it only holds for 2 or 3 years, that’s fine. Who knows how long we’ll stay here anyway, and I can just glue them again in two years. The materials don’t cost much – adhesive and some mortar under 30 euros and maybe a day’s work, if that.

So, what to do? Of course, I’ll talk to the landlord again – it’s getting worse and now the slabs are breaking. But if she still insists, what would a small, low-budget, DIY solution look like that doesn’t aim for durability or perfection?

Thanks and best regards, Manuel

Apply the tile adhesive in a thin layer and press the panels lightly into place.

Rental property: Simply stick it on very pragmatically – as every year again.
Own property: Partially or completely redo it.