If you are converting your loft your plans for the the plumbing must be carefully considered for the simple reason that, by and large, you will wish to have central heating in your new attic extension.
New radiators will be needed for the addition of central heating which may mean that your existing boiler will need upgrading.
If contemplating a Do It Yourself conversion it is important to remember that the plumbing must be one of the first jobs to be completed.
The new water pipes to service the central heating and en-suite bathroom facilities (if needed) need to be installed before the floor and walls are covered.
An exception of course is if you plan to use ‘boxed-in’ surface pipes. But if you are putting in new floors and ceilings anyway the plumbing and electric’s may as well be hidden nice and tidily away.
Installing a new boiler, if required, is the biggest aspect of a new plumbing project though a new hot-water tank may also be needed.
A professional plumber will be able to tell you before any work begins exactly how, or if, your current system will need upgrading and, even if you will be doing some of the work yourself, any work on your gas supply must be carried out by a registered fitter.
That aside, loft conversion plumbing is usually a straight-forward task though, of course, your water tank will need to repositioned.
Much of the work though will be cosmetic, i.e., plastering the pipes behind or into the wall etc.
After the water pipes and any toilet or showering facilities are installed make sure they are thoroughly tested before allowing the plumber off site!
Dependent on agreement with your builders it is a good idea to have your decorating plans already in place at the first fix plumbing stage so that once the walls and ceilings have been plastered you can paint them before putting radiators and other plumbing items in place.
This saves an awful lot of time and inconvenience at a later date.
Structural calculations for loft conversions are of course hugely important to ensure safety and that the proposed plans meet building regulations
What is the difference between planning permission and building regulations approval for loft conversions ?
Using And Fitting Loose Fill Insulation In Your Loft