Do you know what the actual clear span is from front wall plate to back wall plate? as this will dictate the size of beams you will require. The beams rest on the wall plates, are there any noggins in at present in the floor?
Thats what im currently looking for im just unsure on what i should be paying and dont want to be ripped off, a few firms have suggested a few differnt options i just dont know average prices, theres a beam across the bottom, a beam across the top or telebeams
Lets us know when you get back with the quotes. Although no necessary, a plan of all the house would be needed by the SE as well by BC. i/e plans existing and proposed (i.e with loft). Is there space for stairs? If you go steels route then an SE would need to calculate the sizes, so make sure that any quote includes this.
As Jit says 2.4m is not a lot of headroom especially if you're not having a dormer. Telebeams are an option and the guys there are really helpful: you get your design as part of the package but they are quite deep.
I've been on the website and they have 5 different beam sizes, all dictated by the span from wall plate to wall plate. My span was 7.2m so used the T7.0 beams which are 200x70mm. If his span is less the box sections get smaller: 6.2m (175x70mm) 5.8m (150x70mm) Noggins could be removed, but left my noggins is which were 50x50mm, and used a 65mm wall plate packer to clear the beams. So if he dosnt have any then he would get away with 20mm packer to clear the ceiling.
2.4m max, less 150 or more from the floor level coming up less 100 or so off at the rafter for insulation. You want (ideally) 2m headroom over stairs don't forget. adormer would give you much more useable space.
The finished head room in mine is 2.1m, had to put in ceiling collars. This is workable with a 34 degree pitch anything smaller would make the area harder to use, unless its for kids/storage. I was going to go for dormer originally but decided to leave it as would offer much more in the way of space. Insulation: BC allowed 50mm celotex in between rafters, retain, then superquilt over with double batten for air gap. I reckon the span will be small so he will be able to recover some space with the smaller beams. That's hoping that the current trusses would be doubled up using C24 100x50mm.
There are many ways around minimising the amount then floor level comes up. 2.4 m is not a bad staring height we have had to work with less in the past and still work out well
No way can you just cut out the bottom of trusses. They are in tension to stop the roof spreading. With no purlins, if you cut the bottom out of the trusses, there is virtually nothing stopping the weight of the roof trying to flatten out and pushing the roof off the wall plates. You need a structural engineer or a proper loft conversion company.
Liam, if you never done it before get a company to do the 1st fixings for you. If you are installing the beams and are not level it has a knock on effect to the whole floor...staircase..etc.e..etc... One of my ex collegues also thought better and did the whole loft himself and bodged up the steels and ended up spending a fortune correcting. Wiggy , stuctural engineers are a must for this type of work. At the end of the day it is common sense, but you need it in black and white signed off someone who has studied it for years. I see so many people thinking they know it all, then they realize they don't have the experience or skill or expertise to do a high level of finish.