I recently learned this can also be read たきぎ. I don’t know which is more common, but it’s interesting because it’s one of those cases where they take a word that looks like it’s going to be written with kanji X and Y and write it with another completely different kanji. In this case, seeing the hiragana one could guess it would be written 焚き木.
I really like words like this. Other examples include 厩 (stable) and 掌 (palm of one’s hand, this one is even here on WK). Granted, these two can also be written, respectively, 馬屋 and 手の平, though.