New house - loft conversion

[freddiemercurystwin]

They seem quite beefy and there doesn't appear to be any sagging so I'd guess there's a fair chance your roof is adequately supported however not only am I not an engineer but you will not glean an absolute confirmation from a Forum or a book or any other publication. The only way you will guarantee that the remaining structure has left the loft/roof structurally sound is by appointing a structural engineer. They will do a quick survey around an hour and then produce a report say another few hours. It needn't cost that much if you choose a decent engineer. You'll have to do this anyway should you decide to get Building Regulations Regularisation for the conversion. Having said that you could PM or message Static and see if he is prepared to advise. He's a fairly helpful chap

Guides are two a penny on the web: eg http://www.trussloft.co.uk/Downloads/Loft-Conversions-and-the-Building-Regulations.pdf
or http://www.constructionproducts.org...roducts Association Loft Guide March 2010.pdf

as are books: http://www.amazon.co.uk/Loft-Conversion-Manual-Ian-Rock/dp/1844254461/ref=pd_cp_b_0

Out of interest what's that odd timber board on the roof near the gutter? Get a lot of snow where you live?

 

[HammieUK]

I will definitely be appointing a structural engineer (and an architect and a professional builder) when I get this lot sorted, I intend to do a proper job without cutting corners! I'm just after an idea of the work required at the moment to decide whether to do it now or a few years down the line (won't be used until it's up to scratch I might add).

Those links are great, I'll have a good read through them

One last question, when they put in RSJs, is it common to remove the binders (once the celing joist load has been transferred to the new RSJs)? As without doing this, I think the new floor supporting joists would have to sit above the binders, cutting heavily into the room height. Hope that made sense.

As for the timber board, I think it's just there to catch loose tiles or something, there's a conservatory below (another Mr Bodge special, first conservatory I've ever seen with a toilet in it! Don't worry, there's only glass above you ), not sure to be honest though.

 

[freddiemercurystwin]

You can very likely remove the binders, make sure you specify this when you appoint your agent/engineer, the existing ceiling joists can be strapped to the new joists. Obviously the ceiling probably needs to be propped temporarily.

PS you can safely use a Technician for a lofty rather than a fully fledged Architect, they'll generally be cheaper.

 

[Static]

- The house is detached, 14 foot between gables, 16 foot wide.
- There are two steel beams in the attic , running from one gable to the other, these are separated by 12 foot. These are 4" x 4" angle section, 1/3" thickness.

These, in a typical lofty would normally be RSJ's around 180mm in height. spanning between them would be timber joists around 175 in depth. Your loft floor, apart from being very unconventional, sounds hopelessly under-engineered. Building control will, if they don't tell you to rip the lot out and start again, demand calculations from an engineer to prove they work. These will very likely prove the structure is under-engineered. Big-all has very likely hit the nail on the head.

As freddymercurystwin says I would also expect a couple of steel beams around the 180-200mm deep instead of the angle which are really undersized (not run any numbers on them tho)..
Chances are that whoever comes in to do the conversion will rip it all out and start again.. also the engineer may want to see whats hidden behind the scenes..

As you've mentioned the biggest unknown is what was removed from the roof that may be important to the overall structure..