Loft conversion to give double-height living space

[GB]

I can't see how they do the power supply?

[Jim K]

and collect dust and give the spiders somewhere to weave....

How old's the house?

Jim K

[Bert Coules]

That's the best reason yet for getting rid of them.

Early sixties.

[Bert Coules]

Now that is an intriguing notion and it certainly would be less intrusive visually. But imagine the temptation to reach up and try to twang them...

[Bert Coules]

Each fan needs an individual plug-in 12v DC transformer.

[The Natural Philosopher]

yes. the things that tie the rafter ends together. In one place I visit, they replaced (half) those with steel rods. They hang lights off those. A compromise is what I have here. joists are BOLTED to the rafters halfway up, and take the spreading loads.

THis works well with a steep pitched roof - like an old thatched one - and you can either put a ceiling under them or leave them exposed.

[The Natural Philosopher]

yes, or steel rod. That's a bit cheaper. That's what those S and X plates on old buildings are spreader plates for threaded steel rods that go throught the walls are torqued up to hold the walls from bowing.

[Bert Coules]

That's similar to the existing work in my place, except that there are cross-timbers (sub-joists? secondary joists?) fixed to the rafters almost at the height of the ridge board. These were, I think, put in to replace similar but much longer lengths originally fitted halfway between the ridge and the actual joists. Does that mean that the proper joists don't play any significant part in stopping the spreading?

[John Williamson]

I've seen a Victorian roof that used iron rods to take the horizontal tension with a vertical hanger from the peak to hold the mezzanine floor up.

The building is over a century and a half old now, and is still standing.

[Bert Coules]

Well, if I can keep this place standing for even half as long as that, I shall be well satisfied.

[charles]

In primary school physics (c1950) we learned that these steel rods and plates were used to "pull in" bulging walls by heating the steel, tightening up the spreader plates and then allowing the steel to cool.

[Martin Bonner]

They were still teaching that in the 60's. I suspect it's bullshit.

Iron has a coefficent of thermal expansion of about 10^-5/K. So if you heat a 5m rod by 50K, it would expand by 2.5mm. That means you'd have to heat and cool it ten times to get it to pull the walls in by one inch.

Heating it up would be tricky too. What do you do? Play a blowtorch along the length? How do you get access to the whole length? How do avoid setting fire to the joists.

I'm not saying it's impossible - just that I would have thought a fine thread and a bloody long spanner would be much simpler.

[Tim Lamb]

We have *raised tie* ceiling joists in our single story *West Wing*:-)

Mostly they are plaster boarded under and certainly make the rooms feel more spacious.

For the hall, I arranged to have stronger timber used at alternate rafter spacings and the plaster follows the rafter undersides.

Photo here, hopefully.

[Bert Coules]

Tim,

Thanks for the photos. It's a very attractive effect.

[Hugo Nebula]

If you cut through the rafters you will get wet too, as you will have no roof. I presume you mean cutting through _trussed_ rafters? If so, then, yes, this would seriously weaken a roof. However, many houses do not have trussed rafter roofs.

But back to the OP's question. Simply removing the ceiling joists (or in the case of a trussed rafters, the bottom chord and struts) can lead to roof spread, but it can be overcome by ridge beams, purlins, etc. You would also need beams or walls to support the new floor. All of which should be designed by a structural engineer.

If the floor area is less than 50% of the room below it, the total travel distance to the stair should be no more than 7.5m, the stair should discharge within 3m of the door to the room, and there should be remote from the stair (or enclosed within fire resisting construction). Otherwise it is a storey requiring its own means of escape. This can be an escape window. The remaining aspects should be designed as per a normal loft conversion to a single storey dwelling (i.e., smoke detection, stairs, insulation to the underside of the roof, etc.).

[jgh]

I can't make myself not believe that they would just pull the bricks under the plates out of the wall, leaving the rest of the wall where it is.

JGH

[harryagain]

It willbe expensive to do, you will need a new bigger boiler and it will forever be prone to roof leaks. If there are any felt roofs, they will look shit and need replacement every

10-15 years. If not done well, it will spoil the appearance of the building (ie look shit) detracting from the value and making it hard to sell.

Better to move house if you need the space. Or if you are wanting a spare time project, buy a house that is a wreck and do it up. (More profitable) Nopoint in f***g up a perfectly good building/roof.

[harryagain]

You need to remember, if you convert the building into something weird, no-one will buy it when you come to sell. And you will. You will loose a lot of money (twice over). And if it is as extensive as you seem to be talking the BI will want you to employ a structural engineer. More expense.

[polygonum]

I remember someone "explaining" that they would get the blacksmith in to build a fire. But my impression was that that would only be done when the building was dilapidated and had no roof!

Funny what we get taught.

[John Williamson]

In most cases I've seen, the walls haven't been pulled back to the vertical, and the rods are only there to prevent further movement.

If they tried to pull the walls in on a point like that they would, as has been pointed out in this thread, probably fail catastrophically. The materials used to make a brick wall are strong in compression, but relatively weak in shear and tension. This is why the Tudors used to put massive great lumps of brickwork at the top of their chimneys. It kept the stack under a compressive load at all times, and stopped it falling over in a high wind, when the mortar jpints failed under tension on the windward side.