Loft conversion

[PULLMYFINGER]

Hi i was wondering if any one could help me. I'm looking at converting my loft but only upgrading floor to take additional weight. Removing an existing Velux and installing 1 velux cabrio balcony style with the side windows. The current floor timbers are 125mmx50mm and the rafters are 100mmx50mm.

Just so i can work out if i have enough head height after new sized timbers and insulation are added to roof and floor and timber are upgraded

1) Would 200mmx50mm floor beams be adequate
2) Would all the rafters need upgraded to a larger size to carry weight of new roof windows or just cut them out as shown and relocate the purlins to top and bottom with vertical struts from rafters back to new floor beams at the lower side of the velux
3) What sort of depth of insulation should there be allowed in the roof? would this require the deeper rafters to accommodate or would there be nough room.
4) Can the 4No horizontal ties in photo be removed? If they are how do you prevent the rafters from splaying out.
5) Would i require any steelwork added to support the roof to accomodate my proposal. There isnt any dorners but quite a bit of the existing rafters will need to be cut out to accomdate the velux.

I have attached a photo looking from inside and few views from my planning drawing showing how the velux will look inside and out minus any timber / insulation works. But i need to make sure the loft can be converted within regs and i'll have the space inside after new timbers are installed before i waste money on even applying for planning.

Thanks for any help

 

[John D v2.0]

Sounds doable! Posting some dimension ie spans and buildup so the loads can be calculated would make it possible for any SE's on here to advise you.

 

[tony1851]

Almost any roof space can be converted 'within regs'. But to be compliant, it would involve far more than 'upgrading' the floor.
You don't mention access to the loft (ladder? stairs?); and if it is a two-storey house, protection from fire spread and means-of-escape come into the mix.
In terms of Planning; if it is currently a two-storey house, the council might have something to say about the cabrio with side-facing windows.

 

[PULLMYFINGER]

Hi,

There will be a stair case up to the loft and i understand there is a lot more to gaining regs approval than what i have mentioned above. I just need to know what sort of timber sizes i would be expecting to have installed for floor and upgrading of rafters if needed so i can work out if the loft conversion is even feesable for head height without any major works needing done.

 

[John D v2.0]

Well someone on here had a newish big house with a trussed roof,I can't remember the exact span. Anyway he gave the info and everyone said no chance. Then he bought two huge steels in about 5 sections each and fitted them himself, and did the floor conversion and rafter support between those.
So yes it's possible, but we can't suggest how based on your situation

 

[Greenfingaz]

I called my LPA yesterday as also considering a velux loft conversion (I own a fuirst floor flat and the loft space above.

The planning officer I spoke with said that it would most likely need planning if adding skylights. I also asked about whether lowering my ceilings to gain more height in the loft was an issue and he said no as it was an internal thing. Obviously PWA applies and building regs.

I later saw this on the planning portal in relation to the question: I want to build a loft conversion in my top floor flat. The guidance mentioned this "Permission is required where you extend or alter the roof space".

By lowering the ceiling directly below the loft space, would this then be classed as altering the roof space? What does roof space mean in this context? Is planning permission required if lowering a ceiling in order to make loft space larger?

Any advice will be greatly appreciated