Cross battening loft + insulation advice

[samk]

Hello All. Can anyone please advise. I'm hoping to board the loft to use for light storage. When I went up I noticed the state of our insulation. It's really tatty and torn wool type insulation, and is only 10cm deep in some places. In other areas, it's non-existent. I obviously need to increase level of insulation to the recommended 27cm. The joists are 2 x 4 so can only put an initial layer of 10cm (I'll remove all old insulation).
I considered laying the Knauf Supadeck but I'm not a footballer!!!

As such, is it safe for me to cross batten with 2 x 7 or 2 x 8 beams (from B&Q or lumberyard) thus giving me the additional 17.5cm space to increase insulation and also lay down loft boards? Alternatively, should I cut out 2 x 4" blocks and attach these to the joists, THEN lay 2 x 4 beams on these blocks? If either one of these methods is OK, what's the best way to attach the beams to the joists? Can you get 9" or 10" screws? Should I use 90 degree angle brackets? Also what's the best way to safeguard the electrical wiring?

In addition, we've recently had GCH + combi installed and the pipes had to go through the loft space (the pipes are well insulated). Is it safe to insulate around these too? I'm considering boxing these using plywood as there are pipe joins and valves, to allow access should anything go wrong. Any advice? Can I also remove the cold water tank and the raised base it was on? All pipes to the tank have been disconnected and it's completely drained.

I'm a capable DIY'er so long as instructions are easy to follow. Pictures help too!! Any advice is welcome and greatly appreciated.

 

[mattylad]

You'll likely get a response from those that know better, however I'd have thought that just putting 2x8 across laid on top is going to add an awful lot of weight and a fair bit of overkill for "light storage".

That size is more suited for flooring & daily use.

You may also be asked for information on your existing joists thickness, spacings etc.
I bet a picture would say a thousand words though.

 

[samk]

Thanks for your response. The reason I wanted 2x7's is to achieve the required depth for the extra 170mm additional insulation that's required. if not 2x7 then I'd need 2 layers of beams to achieve desired depth. The current joists are 2x4.

 

[PerryOne]

Forget about the recommended thickness of fibre glass insulation and think about closed cell insulation where you can get a better easier to fit insulation.
The problem with most insulation is that it is badly fitted and the heat is lost through the holes.
The best insulation is sprayed or poured foam that fits tight filling every tiny space. This totally eliminated the suction effect of the wind blowing over the home and sucking the warmth out.
You can also store things on top of foam as it will not compress like other insulation's that loose their insulation spec. on compression.
You will have a much lighter stronger warmer ceiling.