Loft Conversion - Rough Ideas

[FBP1]

Hi Paul

Send me your email and I'll send you my plans which will give you some pointers . I don't want my address/ plans all over the web otherwise I'd post them on PH

Basically yes the load for the roof including 3 new dormers is taken by the new steel ridge beam , the short eaves walls ( which pretty much replace the purlins and they in turn stand in the new bigger joists resting on the wall plates in between the old joist which now just hold up the 1st floor ceilings. The new joist fit between the old joists but are about an inch away form the floor/ ceiling below and protrude about 4 inches above the tops of the old joists.

Benefits are less height lost internally compared to having new steels above the existing joists and less buggering about with steels. I'll stick some photos in as well

Edited by FBP1 on Friday 7th November 15:06

[paulrockliffe]

Thanks John, that's great. I've sent you an email just now.

[Neil - YVM]

Alucidnation said:

Hate to be rude OP, but to me it seems you haven't got a clue what you are doing.

I suggest you get some proper plans drawn up by a decent architect and go from there.

Ouch.

[Triumph Man]

Little Lofty said:

You can use intumescent varnish but it's more like treacle than varnish. Fire rated glass doesn't need to be wired, you can get clear glass but it is pretty expensive. You don't need a fire escape from the loft, that's what the protected route is for.

Yeah it's pretty 'orrible stuff and can look ste.

[Little Lofty]

FBP1 said:

Hi Paul

John or Fat Boy here.

Send me your email and I'll send you my plans which will give you some pointers . I don't want my address/ plans all over the web otherwise I'd post them on PH

Basically yes the load for the roof including 3 new dormers is taken by the new steel ridge beam , the short eaves walls ( which pretty much replace the purlins and they in turn stand in the new bigger joists resting on the wall plates in between the old joist which now just hold up the 1st floor ceilings. The new joist fit between the old joists but are about an inch away form the floor/ ceiling below and protrude about 4 inches above the tops of the old joists.

Benefits are less height lost internally compared to having new steels above the existing joists and less buggering about with steels. I'll stick some photos in as well

I'd have to disagree, with steel in place you can hang smaller timbers off the steel beam. As the steel shortens the span, the joists are smaller so will create more headroom not less. The OP states the house is 10m deep so each timber will have to span 5.0, ( that's assuming there is a load bearing wall in the centre of the house) this is on the limit for even a 225x50, 150x50 could be used if steel is used so giving an extra 75mm of headroom. This may or may not be critical, but no matter, steel will nearly always allow more headroom. Also depending on the roof detail it's not always possible to have a joist resting on the inner leaf as it may have to be cut on too great an angle, greatly reducing its strength.
OP, I know a guy who lives in Chester -Le- street would do your plans if your stuck, also with the greatest respect to your brother, some of the calcs I've seen for lofts are outrageously over the top, make sure the couple of hundred saved by not using a structural engineer familiar with lofts isn't eaten up by over the top timbers and steels.

[paulrockliffe]

Little Lofty said:

I'd have to disagree, with steel in place you can hang smaller timbers off the steel beam. As the steel shortens the span, the joists are smaller so will create more headroom not less. The OP states the house is 10m deep so each timber will have to span 5.0, ( that's assuming there is a load bearing wall in the centre of the house) this is on the limit for even a 225x50, 150x50 could be used if steel is used so giving an extra 75mm of headroom. This may or may not be critical, but no matter, steel will nearly always allow more headroom. Also depending on the roof detail it's not always possible to have a joist resting on the inner leaf as it may have to be cut on too great an angle, greatly reducing its strength.
OP, I know a guy who lives in Chester -Le- street would do your plans if your stuck, also with the greatest respect to your brother, some of the calcs I've seen for lofts are outrageously over the top, make sure the couple of hundred saved by not using a structural engineer familiar with lofts isn't eaten up by over the top timbers and steels.

Thanks that's useful. I'll measure the spans at some point and put a diagram up. I suspect they're closer to 4.5m and I'd think there's room to get the timber to the inner wall without mitring the top edge too much, from memory there's a good gap to the underside of the roof there, I tihnk you can get your head in it. I'd have guessed bigger timbers would be available than 225 x 50 though?

The ground floor joists are 3" x 8" and span the same gap, though I appreciate the loading is different.

The spine wall in the middle of the house extends a little over half the width of the house, so I wondered if it was feasible to sister up the 8" x 3" joist that's part of the King Truss that extends front to back and is supported on the spine wall. From this I could then run run joists from this to the side of the house, these would all be a little under 3m wide. Would need a wall plate. Probably better with a diagram really.

Joists from front to back would be easier to support at the wall end, but would mean longer timbers. 5m might not be too far off the limit of what I can physically get in through the house. Would it be better to transfer load to all four walls or are the walls generally so over-engineered that it doesn’t really make much difference?

Steel wouldn't lower the floor height unless the king truss then came out because the floor will likely be raised to the height of the lower joist in this truss structure. Mind you, if a steel at apex level let me remove the king truss entirely without huge knock-on costs elsewhere it might be worth the cost as with the truss in place I'll end up with a smaller bedroom and a larger bathroom than I'd prefer.

You might be right regarding the level of calcs required, my brother designs commerical buildings, hospitals, bus stations etc, so I don't know how in tune he would be to the requirements of BC, but I would think I could get a list of everything they need to know and tailor his work to that. I'll bear your contact in mind when we get to that stage, though it may not be for quite a while!

I was going to measure up tonight as I've a free evening, but my girlfriends car conked out last night, so I'll be messing about with that instead.

[FBP1]

I wont argue with you LL as you're the professional here. I'm just saying it has worked for our set up very well and with my house being basically pretty much square at approx 9 - 10 X 10m then its not that different in pure plan, although I do have the benefit of spine walls to take some load running up the top floor alongside the central hall stairwell arrangement in my place. I also have a terraced house with shared flues in the party walls exactly where floor steels would normally run

The new floor in mine is rock solid and, including the finished 21mm screwed and glued T&G, is definitely no more than 75-100m higher than the top of the old joists - probably the same height as the old binders that ran across the old joists. Perhaps my old joists are deeper than the norm.

The OP should get some advice - I'm fully with you on that- as I went the whole architect/ structural calcs, full building regs drawings/ professional builder approach and all architects will give you a free introductory hour, but as a "lets have a think about it" session there's no harm in considering all options.

The structural engineer had no issues with our floor approach and most of the houses in my road have gone the same way so maybe there are just particular wrinkles in these houses.

OP one thing i found useful was snooping around the local authority online planning application site for my area as you can usually see all the planning drawings and building reg drawings so you can build up a picture of how its done with your sort of house in the area.

[Busa mav]

Little Lofty said:

, some of the calcs I've seen for lofts are outrageously over the top, make sure the couple of hundred saved by not using a structural engineer familiar with lofts isn't eaten up by over the top timbers and steels.

Exactly my thoughts on this ,

Any engineer not used to designing loft conversions could leave you with something like the pigs ear that has been posted up earlier.

[Little Lofty]

Busa mav said:

Exactly my thoughts on this ,

Any engineer not used to designing loft conversions could leave you with something like the pigs ear that has been posted up earlier.

One of the worst and most complicated lofts I done was down to the fact that the house owner got his friend who lived 200 miles to do the drawings and calcs, he probably saved £2/300 but I could have saved him £2/3k if I'd had the plans drawn. I stopped doing lofts for people who already had drawings, as most of the time they were complete crap and I was always the mug who had to sort it all out.
As I said OP no offence to your brother, but from experience very few architects can do lofts and most engineers just over complicate things. £1200 would cover the drawings, calcs and building regs, it may be a few quid more now but not far away.

[paulrockliffe]

All taken on board, thanks.

[Little Lofty]

FBP1 said:

I wont argue with you LL as you're the professional here. I'm just saying it has worked for our set up very well and with my house being basically pretty much square at approx 9 - 10 X 10m then its not that different in pure plan, although I do have the benefit of spine walls to take some load running up the top floor alongside the central hall stairwell arrangement in my place. I also have a terraced house with shared flues in the party walls exactly where floor steels would normally run

The new floor in mine is rock solid and, including the finished 21mm screwed and glued T&G, is definitely no more than 75-100m higher than the top of the old joists - probably the same height as the old binders that ran across the old joists. Perhaps my old joists are deeper than the norm.

The OP should get some advice - I'm fully with you on that- as I went the whole architect/ structural calcs, full building regs drawings/ professional builder approach and all architects will give you a free introductory hour, but as a "lets have a think about it" session there's no harm in considering all options.

The structural engineer had no issues with our floor approach and most of the houses in my road have gone the same way so maybe there are just particular wrinkles in these houses.

OP one thing i found useful was snooping around the local authority online planning application site for my area as you can usually see all the planning drawings and building reg drawings so you can build up a picture of how its done with your sort of house in the area.

Yes nothing wrong with your conversion but as I mentioned earlier I have done conversions using only timber, generally 9x3's. However I found it easer, quicker and just as cheap to use steel and 6x2's, you usually also gained some headroom, which when it comes to getting in showers etc every millimetres counts.
OP, 9x3's are about as big as it gets for stock timber. The spine wall ending just after the tie beam is quite usual, we usually tripled up the floor joists at that point, doubled up a trimmer that hangs off the triple joist and sits in the wall, the floor joists then hang off the doubler, probably sounds double Dutch but it's pretty straight forward, I'll try and dig out some old plans and post up some pics. As I mentioned, I'd be happy to look at it for you at some point.

[paulrockliffe]

Thanks, that's great!

I had a quick look earlier as I'm putting off going out in the cold to fix this car.

I think the issue with steels in the floor will be that to run them across the shorter length means removing that tie beambefore there's anything in to replace it. And the long length would require more steel and probably more than can be inserted without a crane.

The span from the tie beam across to the gable wall looks comfortable for wood rather than steel to my untrained eye.

If I can get a proper floor in first then it makes the rest much easier as I have something to prop the roof off while putting a steel in at ridge level and removing the king truss.

[Little Lofty]

The steel normally sits just above the tie beam, then we would bolt a timber into the web of the steel and use joist hangers to get the new floor joists as close as possible to the existing ceiling. A typical steel beam would be 5.5 to 6.0 long, spilt into three they are easy(ish) to get into the loft, as long as you you have three weetabix of course

[Gtom]

Busa mav said:

Exactly my thoughts on this ,

Any engineer not used to designing loft conversions could leave you with something like the pigs ear that has been posted up earlier.

You mean the one I posted up?

Explain because it's nearly done now and everything has gone just fine.

Btw the 'pigs ear' was my drawing that I sent to the architect showing him what I wanted.

Edited by Gtom on Friday 7th November 19:43

[Tony427]

Anyone ever used these guys as a solution to steel and flooring issues?

http://www.telebeam.co.uk/

Tony