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- 14 Jun 2023
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Short version:
I'm planning to pour Mapei 3240 SLC onto the rather rough concrete screed (which is damaged in some places) in my flat, in which are laid underfloor heating cables. 3240 has a compression strength of about 25N/mm^2 and it's flexible so I hope it might be suitable as a finished floor, but if not how should I finish it? I'm looking for a smooth finish suitable for a domestic flat that's easy to clean, doesn't show up dust or debris too much, and looks "neutral" or "industrial". I'm going to do two small experimental areas (the kitchen and hallway) before committing to the whole flat if they work out. Previously I tried simply painting these areas, but the paint shows the roughness and imperfections of the concrete screed, and the paint collects marks that are hard to clean off.
Any advice very welcome!
More details in the long version:
My flat in the Barbican is built of solid concrete, with electric
underfloor heating cables laid under about 40mm of concrete screed.
The flat is mostly carpeted, with gripper rods glued to the screed
back in 1973 when it was built, so they are hard to remove. Bashing
the carpet gripper rods with a scraper and a mallet tends to either
leave some of the adhesive behind on the screed, or to bring up some
chunks of crumbly screed, so something would be needed to smooth or
fill the edges of the screed once I've removed all the gripper rods.
Also there's an expansion gap, which could perhaps be filled with a
sufficiently flexible material. The screed itself is very flat but
it's got quite a grainy surface.
I experimented with "Rustoleum chalky finish floor paint" about 5
years ago in a couple of small rooms. In the entrance hall I pulled up
the gripper rods and filled and smoothed the damaged screed edges with
Ardex feather finish, which I found quite satisfying so I ended up
smoothing a thin layer across the whole surface of the screed. I
painted directly onto this. The paint looked nice but shows my poor
skimming skills: you can see trowel marks if the light is right, and
you can see brush marks in the paint where I was lazy. After 5 years
the floor is smooth but quite grubby. It cleans up with soap and water
and elbow grease but it's not a low-maintenance surface.
In the kitchen there was vinyl stuck directly to the screed. No
gripper rods, so I didn't skim the floor, I just pulled up the vinyl,
scraped off the worst of the adhesive and painted the Rustoleum
straight on. It looked OK, though you could see the traces of the
notched-troweled vinyl adhesive showing through. The paint surface is
rougher than the entrance, because I painted directly onto the screed
and so all the little pits in the surface fill with kitchen muck. It's
hard to clean, and honestly I'd just paint on another coat if King
Charles was coming round for tea, rather than try to clean it up with
a mop.
OK, that's the story so far! I want to do the whole flat (65 sqm), but
I don't want to do it all at once, as I live here and would need to
move furniture around to do a section at a time. I would consider
doing a single room as an experiment to see how I like it, as I have
previously (described above). Also, I don't mind taking a bit of a
risk as long as I'm not spending too much time or money on it. For
comparison, my neighbour recently had a resin floor professionally
done. It looks amazing but cost £15k and of course he had to empty
everything out of his flat and vacate for a month, so I want to DIY something
that's >50% as good for <10% of the cost!
I'm planning to pour Mapei 3240 SLC onto the rather rough concrete screed (which is damaged in some places) in my flat, in which are laid underfloor heating cables. 3240 has a compression strength of about 25N/mm^2 and it's flexible so I hope it might be suitable as a finished floor, but if not how should I finish it? I'm looking for a smooth finish suitable for a domestic flat that's easy to clean, doesn't show up dust or debris too much, and looks "neutral" or "industrial". I'm going to do two small experimental areas (the kitchen and hallway) before committing to the whole flat if they work out. Previously I tried simply painting these areas, but the paint shows the roughness and imperfections of the concrete screed, and the paint collects marks that are hard to clean off.
Any advice very welcome!
More details in the long version:
My flat in the Barbican is built of solid concrete, with electric
underfloor heating cables laid under about 40mm of concrete screed.
The flat is mostly carpeted, with gripper rods glued to the screed
back in 1973 when it was built, so they are hard to remove. Bashing
the carpet gripper rods with a scraper and a mallet tends to either
leave some of the adhesive behind on the screed, or to bring up some
chunks of crumbly screed, so something would be needed to smooth or
fill the edges of the screed once I've removed all the gripper rods.
Also there's an expansion gap, which could perhaps be filled with a
sufficiently flexible material. The screed itself is very flat but
it's got quite a grainy surface.
I experimented with "Rustoleum chalky finish floor paint" about 5
years ago in a couple of small rooms. In the entrance hall I pulled up
the gripper rods and filled and smoothed the damaged screed edges with
Ardex feather finish, which I found quite satisfying so I ended up
smoothing a thin layer across the whole surface of the screed. I
painted directly onto this. The paint looked nice but shows my poor
skimming skills: you can see trowel marks if the light is right, and
you can see brush marks in the paint where I was lazy. After 5 years
the floor is smooth but quite grubby. It cleans up with soap and water
and elbow grease but it's not a low-maintenance surface.
In the kitchen there was vinyl stuck directly to the screed. No
gripper rods, so I didn't skim the floor, I just pulled up the vinyl,
scraped off the worst of the adhesive and painted the Rustoleum
straight on. It looked OK, though you could see the traces of the
notched-troweled vinyl adhesive showing through. The paint surface is
rougher than the entrance, because I painted directly onto the screed
and so all the little pits in the surface fill with kitchen muck. It's
hard to clean, and honestly I'd just paint on another coat if King
Charles was coming round for tea, rather than try to clean it up with
a mop.
OK, that's the story so far! I want to do the whole flat (65 sqm), but
I don't want to do it all at once, as I live here and would need to
move furniture around to do a section at a time. I would consider
doing a single room as an experiment to see how I like it, as I have
previously (described above). Also, I don't mind taking a bit of a
risk as long as I'm not spending too much time or money on it. For
comparison, my neighbour recently had a resin floor professionally
done. It looks amazing but cost £15k and of course he had to empty
everything out of his flat and vacate for a month, so I want to DIY something
that's >50% as good for <10% of the cost!