Building rgulations and roof woodwork

[bt0558]

I am an amateur at this sort of stuff so if i use wrong words please be patient.

I have a 3 year old chalet bungalow that has 94wx98h (GGL P04) velux window in back bedroom above head height. I now have planning permission to install an addition window of the same type below the existing window.

The existing window is installed tight between 175x50 joists which have been doubled up when the place was built. Above and below the new window are 175x50 single stretchers (i think this is the term).

There will be 100mm between windows which it seems is normal for flashings etc.

My options seem to be to leave the existing lower stretcher in place or double it with an additional stretcher and place either single or double stretchers below which I would attach to "crippled?" rafter below after cutting and sides.

I wish to make the stretcher below the existing window much narrowr so would like to replace it with 50x50 so it would not be so intrusive inside.

Do you guys think I would get away with place a double 50x50 between the two frames and then a double 175x50 below the new lower frame?

Building regs must have agreed the original with one stretcher rather than 2.

I wish to do the job and take loads of photos and then ask for retrospective BR approval which may not be the best approach. If worst comes to worst can replace middle stretchers.

Also if I did decide to go for BR before doing the job would I need to get professional drawings etc.

Can anyone advise please?

 

[bt0558]

May be trimmers not stretchers.

 

[^woody^]

The trimmers don't do a lot, so no need to double these up

You can put your new window as close or far from the existing as you like, or as required by the top gutter kit.

The existing joists will be fine with the load from this new window

I would not bother with b/regs. If you do you don't need plans - use a Building Notice form

 

[bt0558]

Thanks for the reply woody, much appreciated.

What I have talked about as stretchers and trimmers might actually be noggins although they are same size as rafters ie. 175 x 50.

Would noggins be doubled up at bottom and if i read you right you are saying I could remove the "noggin" at the bottom of the existing window and move the windows up as close as the brackets will allow.

 

[^woody^]

The timber between rafters are normally trimmers inserted to support a cut/crippled rafter - otherwise it will have no support at the opening

These do carry a small load of the cut rafter, but not a great deal

If you have a timber which is functioning as a noggin (with no cut rafter fixed to it) then this is not doing anything other than being there to fix plasterboard to

So basically, you don't need to double up any timbers between the rafters

 

[bt0558]

Thats brilliant woody thank you.

Great advice that even I can understand.

 

[tkmax]

I would not bother with b/regs

I would. Although it sounds like no significant structural alteration is required the installation of a new window is controllable works. Building Notice would be fine.