Any cement based grout which is the most commonly used grout is not waterproof. Water resistant, but not water proof. Epoxy grout on the other hand is, but it is not as common.

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modern grout is waterproof

I'll try the wedging thing tomorrow, Ran out of light today.

I'm being quite gentle with the cut, letting it pull me along.

If it messes up my only other long hardwood blade tomorrow I'll go find time in a makers space.

Thick enough? Concrete is not hydrophopic. It gets wet and soaks water mate.

Easier to work on a concrete slab than? A packed sand/stone floor? Just a waste of money pouring 2 concrete slabs imo. Theres no problem packing and leveling without concrete

If your cut is closing in on itself it may be causing the blade to drift. Try wedging the cut as you go. Also try slowing the pressure down, give it more time to cut.

Jigsaw blades are "bendy" so might not be the best tool for the job.

The first blade I bent was for 50mm thick hardwood, and Ive seen a few people online succeed in long straight cuts.

but after a bit more playing around I may need to go find somewhere that will let me use their table saw. I'm thinking the entry level jigsaw I have isn't up to keeping things straight for that distance.

In Germany they are not required, only smoke alarms are.

You will struggle with a jigsaw. Buying a blade specifically for hard wood might help but a track saw or table saw are much better options.

It does when it's thick enough and/or you add the right additives.

It's also easier to work on with your insulation.

There is no single answer.

Like others have said, caulk (silicone) is available with many colours. It is available from same stores that sell tiles and grout (and other stuff for building the shower room from scratch).

In a normal bathroom, the stuff (grout) between tiles is porous and let's water flow through it. It is not for sealing at all. Usually the caulk (silicone) is used on "moving seams" where grout would crack. This is seals between walls, between walls and floor etc.. Most times, caulk is not sealing anything. Water has path around it via the porous grout. Depends on place what the purpose of the caulk is. Most times there is polymer "water insulation" layer UNDER the tiles/grout/caulk in shower rooms, ending up to sever hole. This polymer water insulation has been added before the tiles to floor and walls (it is fiber enforced polymer stuff that solidifies into flexy rubberlike plate). Caulk is in this case for visual esthetics and mechanically protecting the actual water insulation layer.

I have built my shower room and sauna myself for my latest house, so I have practical experience. The best way for caulking has been to put painters tape next to the seam on both sides (leave a few mm from edge of tile), put the caulk in place with the tool (pushing it out from the tubular container), and use a silicone tool to form the caulk seam (the silicone tool has several radiuses - and remember to put water or soap water on the tool - you could use finger instead of tool, but tool is cheap and you have always same radius with tool). Then remove the painters tape (don't wait for silicone to harden, you have to remove tape after applying silicone) and you have a perfect seam with no smears.

I know pros do it without the tape, but I have made the best seams with the tape. It looks always perfect like that with no smears.

Try it out first somewhere else. If nothing else, take a cardboard box and make seams to the inside corners to try!

Concrete does not stop moisture. The walls go further down than the floor does so that doesnt make a difference

The concrete supports your walls at their base and keeps moisture from coming through your floor from the earth.

First step is cleaning the grout. It’s likely a lighter color than what you’re seeing, unless you purchased a brand new condo.

And then, follow the rest of the advice. I like to use a wet finger to smooth the caulk, spending money on a tool is unnecessary.

Great work. Terrible camera angle lol

Ah! That’s a good theory

To be able to put floor heating on it, + it has an insulation property. You cant put floor heating on styrofoam, so you need a layer of something else. And these boards are stuff and sturdy and are approved for floor heating, theyre perfect

THANKS LISA!

Haha, its safe. Everyone has it here

Haha, thank you very much :)

Why use a waterproof substrate if you don't want to actually waterproof it?

She said "meow".

No xD

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