Yes, this what we told too.

Same when we did our back deck. We made it bigger than it was and it was bit rickety due to age. CRA said repairing the existing structure is maintenance. Because it would be used by both daycare and family, then we could claim maintenance of it at usual percentage. Could claim all material for repairs, replacement wood where needed, screws, stain when done, that all fine.

But the addition bit would be an improvement. It not maintaining what we had but new and better than what we had. That potentially mean home improvement boost value of asset. It not claimable because our house is personal asset not business asset. So the wood, screws, stain for the new part could not be claimed.