Sorry, not VAT - but the value of the benefit you gain from working on your own property (presumably also if you're, say, a car mechanic and work on your own car, etc.) is subject to taxation. Mea culpa.
The obligation to pay tax only kicks in (as far as I can tell, IANAL) if the work is substantial and of a nature which requires professional skills.
Here's a recent link, though in Norwegian, I'm afraid:
Jesus! Spinning this forward, this means: If I'm a professional wealth manager and I manage my own wealth during working hours (because office not busy right now), then I would have to pay taxes because I'm a finance pro applying my own skills on my own stock portfolio?
IANAL, and I have only heard about a couple of cases where people have been taxed under this statute - typically carpenters having built or renovated their own homes or cottages.
(Their obvious disadvantage being, of course, that the result of their labour is very tangible - and that whenever you do any significant building work, you'll need permits and documentation afterwards, making it difficult to discreetly renovate something off the books...)
I have seen very wierd tax laws in other EU countries, but this is really "fresh": In that case I would somehow try to do it without someone noticing (so treat your neighbours well :-D) - this is similar to collect taxes on food that Ive grown on my balcony
I read the Norwegian article that was linked, and it isn't actually similar: you would only have to pay taxes on food you've grown on your balcony (and mean to consume yourself) if you are a farmer, are growing it during regular working hours, and have an insanely huge balcony.
Another thing that makes home construction a bit different in this regard is that you could claim to build a house for yourself, live in it for a bit, and then sell it on a couple of years later. That'd be an easy way to avoid or evade taxes. Not so easy with lettuce -- once you've eaten it, you've eaten it.
If a Norwegian tradesman works on his own home, he's supposed to pay VAT on the value of the work he's done - not only on the materials used.
I suspect such work is being under-reported, though.