Joe Schmidt has hinted Wales broke protocol in asking Six Nations bosses to close the Principality Stadium roof in Saturday's tournament decider in Cardiff.

Under Guinness Six Nations rules, both teams would have to agree for the Principality Stadium roof to be closed in the weekend's denouement.

Schmidt revealed Wales asked Six Nations chiefs for the roof to be closed due to poor weather forecasts, leaving the Ireland head coach mildly vexed but pledging to adapt either way.

Ireland still should receive the final say on the roof but Schmidt refused to be drawn, simply insisting his team would cope one way or another.

"There's been a request from Wales that in the interest of the quality of the game and the very poor weather forecast that the roof be closed," said Schmidt.

"So they've said to the Six Nations directly, 'can it be closed?'"

When it was put to Schmidt that normally the visitors would be asked to decide on the roof, Schmidt replied: "Yes, normally, normally."

And when asked what Ireland want, Schmidt continued: "We'll adapt, we'll adapt.

"At the moment I'm not sure about the roof."

Munster lock Tadhg Beirne will make his Six Nations debut as Ireland bid to deny Wales a first Grand Slam in six years.

Ireland boss Schmidt fears closing the roof could make precious little difference in any case, recalling how he believes Wales over-watered the pitch back in 2017, when the hosts prevailed 22-9.

"For us, last time we said 'look, we don't mind, you choose'," said Schmidt.

"And they chose closed, but made the field incredibly wet at the start of the game.

"So we will probably be happy enough if it's open anyway.

"We'll adapt to whatever conditions the game's played in.

"And if the Six Nations decide that it's going to be closed, well it will be closed and we'll play in those conditions.

"And if they decide that it's open, then we'll play in those conditions.

"For us, I think, the last time it was closed we arrived there and there was a lot said about making it good for spectators.

"And then the sprinklers were on for 30 minutes and the ground was very, very damp before the game started.

"So that probably enters into our minds about which closed is it going to be? Is it going to be closed and wet, or is it going to be closed and dry?

"If it's closed and wet, we might as well have the roof open and let the rain come in."

Wales boss Warren Gatland confirmed he was waiting on a final decision, but expected Ireland to ask for the roof to be open.

"We have not heard definitively but we understand they want it open, which is not a concern for us," said Gatland.

"My only concern is that if it is pouring down with rain then we do have a responsibility to the game for a spectacle.

"That's a decision that is out of my hands. Both teams have to agree to the roof being closed so that means basically the away team decides what happens in our stadium.

"I have made a number of comments in the past about that. It's our stadium and we should be able to do what we want with it."