extending rooms

[geffers123]

i want to ajoin 2 x rooms into one via french windows through a non load bearing internal wall but for peice of mind i would like to put in a lintel anyway. can it be done? what size lintel do i need? do i need planning permission as it is not supporting anything?

[archtext]

[quote="geffers123"]i want to ajoin 2 x rooms into one via french windows through a non load bearing internal wall but for peice of mind i would like to put in a lintel anyway. can it be done? what size lintel do i need? do i need planning permission as it is not supporting anything?[/quote]
If the wall is non loadbearing then I assume you mean to put in a lintel which will support the remaining 300mm pprox of wall above the new opening.
You do not say what the wall is constructed from.
DO not assume that if the wall is made from stud(wood frame ) partition that it is not loadbearing.
There could be a partition above it or the partition could be breaking the span of floor joists resting on it or even partly across it via cross members.
A partition above could in turn be supporting or breaking the span of ceiling rafters at first floor.
Lintel manufacturers can often offer assistance with basic information,sizing
but recommend structural engineer. See also Catnic lintels, IG lintels.
Take Care!
You do not need planning permission unless your building is listed but alterations should be referred to building control. In the case of the "french windows" there are building regulations governing these.