Sub floor has to be perfect absolutely perfect. It's so thin it'll show every lump bump and board joint.
I'd rather use an engineered board with an underlay.
Any reason you want to use karndean?
Just had my living room done using Polyfloor Camaro LVT. I was so happy with result I’ve had my hallway done too, but with a Harvey Maria and Polyfloor mix.
Floors were first levelled with self levelling compound as my existing subfloors were poo. So easy to clean and a long warranty, expensive, but so would alternatives line engineered wood.

any chance of a photo or tw
When I bought my new build apartment in 2015 I had wood effect Karndean installed in hallways, lounge and kitchen. No complaints, thought it was pretty good and looked nice. Had Amtico tiles installed in the bathrooms, I ended up just going for the designs I preferred - didn't see much difference in the quality between the two personally.
Weve got Karndean down in our living room over electric underfloor heating, we are pleased with it now, but we had lots of problems, nothing to do with the material, just a **** floor fitter.
It's sorted now though.
What problems did you have? I've got problems with my flooring which is both down to fitters and product!
We found there was more choice with the Amtico. Seemed to be able to choose bevelled edges etc, whereas with Karndean each range came as it did. However in the end the design we preferred ended up being one of the cheaper Karndean ones.
Our floor isn't level in the slightest to the point it's comical, our fitter suggested it was still suitable and he just evened out the main dips rather than getting it completely flat as it would've been a huge/expensive job. It's only been 18 months so far but no issues yet.
Ok, so, we had it fitted over electric under floor heating, the electrician did a pretty good job screeding the floor, even the floor fitter who had originally quoted us for 2 rounds it screed said they did a good job and we would only need one. They also used heat resistant glue (apparently) as were well aware the heating was under before taking the job.
That done, floor fitted, looked fantastic.
It was November and chilli, new floor, living room decorated, all cosy though wack on the underfloor heating, enjoy a movie.
What they failed to tell us is that for a good few weeks you are not supposed to put heating on under, and then go very gently for a few more weeks after until it all settles in.
Blew the bloody flooring up, basically it expanded into itself at all the joints, which then lifted.
To be fair, they were ok about it after, but came 3 separate times to do patch jobs until we got fed up and they eventually agreed to relay the entire floor.
Obviously each time this meant emptying the furniture out of the room etc, pain in the backside.
It's all sorted now though and looks fine, I did drag a piano across it where one of the casters had seized, and you can hardly see it, which isn't bad considering if you've ever moved a piano you'll know how heavy they are.