French farmhouse renovation - roof window

Nick Inman charts the ups and downs ofdoing it himself with tips and information he has learned renovating a French farmhouse. This month: Fitting a roof window need not be a hole lot of trouble

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Some DIY jobs you need to think about carefully – you need to know your limits.

However, there are a few that are best done in a spirit of rash overconfidence, otherwise you don’t do them at all.

One of the latter kind is fitting a skylight, because it involves hacking a huge hole in a perfectly good, watertight roof.

Converting the huge loft into bedrooms and bathrooms was one of the main reasons for buying our house but that dark and dead zone was going to need of a lot of light bringing into it – three large new windows on the north side, to be precise.

I saved a small fortune doing the job myself but it was way out of my comfort zone.

Actually, if I am honest, fitting a roof window involves both planning and impulsiveness. You can’t do enough measuring and staring but there comes a point when you have to start shifting tiles and sawing through rafters.

There are several points that have to be considered with precision before you make the cut.

The first is to not only calculate the exact location and dimensions of the opening you are going to need, but also to ensure that any timbers you saw through will be supported by various inserts. Roofs are heavy things and they will find the weak spot if you leave one.

Even more important is to look at the outside of the roof and be sure you have thought about running water.

It is easy to create a soft spot near the new window where the rain will accumulate and eventually soak through.

Another thing is how you are going to open and close the window. If you can afford it, it’s worth going for a motorised system, including blinds.

I spent days marking the timbers and game-planning all the things that could go wrong.

I did my reinforcing and waited for a fine day with no prospect of rain.

I also did a lot of stockpiling of tools and fixings, and running extension leads. You need things to hand when you are on the top of a ladder.

When I was guaranteed two rain-free days – one to do the job and one because something was bound to go wrong – it was time to do it. After that, there could be no stopping until it was done.

I got up a ladder and started prising loose the tiles and making piles of them next to the opening. I cut through the requisite timbers and fitted and refitted the frame of the roof window until it was just right.

When that was fixed in place, I got to the second hardest part, shaping tiles with an angle grinder so that I could fit them snugly around the window, along with the flashing supplied by the manufacturer.

The hardest part of all was fitting the window proper (the pivoting “light”) into the frame, which involved manipulating a heavy, double-glazed brute at the top of the ladder with only a narrow opening to let the both of us pass.

It was a piece of cake, really.

Sadly, 10 years and a bit later, I got a nasty shock. Damp had seeped through and was creating mould on the inside.

The window was just out of guarantee and I assumed that the manufacturer – so famous that its name is synonymous with roof windows – would at least meet me halfway in replacing it so that I didn’t have to moan about them in print.

They weren’t interested. So much for aftersales service. Next time, I’ll choose a cheaper, less well-known brand.

However, before you even dig out your ladder, see what permission you might need.

Officially, you need approval from the town hall. They will probably want to know if you are extending your living space and therefore going up into a higher local tax bracket.

If the new window is not visible to the neighbours, there should be no problem.

If you live in a conservation area, you will probably be told to go and talk to Bâtiments de France ( as well.