John points out he has been quoted €35,000 to reroof the house with a slate roof, which would require far less maintenance.
They're in the process of carrying out a 'step thatch' on the roof, a cheaper alternative to re-thatching it completely, costing around €12,000.
But he says this will have to be done again in another seven to 10 years.
Emma Byrne, author of the newly published 'Irish Thatch', has had a more positive experience since she bought her thatched home in Co Wexford eight years ago.
She says she wrote the book as a celebration of Irish thatched houses throughout Ireland.
Yet she admits she is also conscious of the difficulties associated with living in one.
The most significant one of these, she says, is the cost of insurance which is currently only covered by one provider.
"There are around 3,000 thatched cottages that are protected in Ireland, which tells me people up and down the country are still looking after them because they're important to them," she says.
In 2014 she completely re-thatched her cottage with grant assistance of 80pc from the Department of Arts, Heritage and the Gaeltacht's 'Mayo Grant', and Wexford County Council.
She said the publication of the Department's guide for thatched owners last year is also hugely beneficial.
"When we bought the house first we hadn't a clue where to go for grants or information about them.
"I also did a lot of research and shopped around for a thatcher, which involved talking to the owners of other thatched houses and asking them who did their roof.
"There are difficulties with them as there are with any old house but they are also an important part of our heritage.
"And you don't hear any Priory Hall stories about thatched houses," she added.
But for the Lenihans, the high cost is why he thinks his mother will be the last family member to live in the house.
They have thought about trying to get the house delisted but were advised they probably wouldn't be successful.
"My mother is a widow in her mid 70s living in the house on her own and surviving on a non-contributory State pension," says John.
"Her house is in the farmyard so it's of no monetary value as we can't sell it. Realistically, if it was anywhere else on the farm we probably would have sold it and built something onto our own house for her.
"The roof has always been an issue and I can always remember it leaking and water flowing down the walls," he said.
"Whenever my mother could afford to get a thatcher, she'd get it done but they were local that time whereas now all the local tradesmen are dead and gone."
He says it's also up to the owner to chase the grants and his mother is probably in a better position than many other elderly people because she has someone to do this on her behalf.
If the house is not maintained, she is liable to face a fine or even a jail term.
"The Department of Heritage is supposed to be protecting that building for the State and yet they won't let me put a new roof on it that would secure it for another 100 years," John adds.
What he would like to see happening is that either his mother's house is delisted, which would allow her to put a lower maintenance slate roof on it, or else that she gets adequate funding to help maintain it to a proper standard.
He says both the Department of Heritage and the Department of the Environment cannot afford to fund the cost of maintenance to every thatched roof so they should strategically pick some of the most important thatched structures and concentrate on those.
"We love the thatched roof because it's our old home but with the the cost that feeling is deteriorating quickly," he says.