Thread: Setting out a hip roof

It would be handy for a DIYer but probably not for a chippy

Originally Posted by echnidna

It would be handy for a DIYer but probably not for a chippy

Why not? "True positioning" is a superior method of setting out measurements. Point-to-point is prone to error by accumulation of tolerances.

Cheers,
Joe

Looks handy to me. The cutting angles make it useful. I have always dragged a rafter up on the roof, marked in place, take it down to cut, back up to check, back down to use as a master. After making myself crazy figuring stairs, the stair section looks good.

Thanks Echnidna, Joe and Paul

I've added running measurements to the metric roof calculator
http://www.blocklayer.com/roof

Check the 'Running Setout Points' box above the Calculate button and it will display the 3 sets of running measurements, Ridge, Wall and Hip

It could look a bit complicated at first glance, with odd looking measurements, especially how the hip run starts at the side cut, and that if you mark out the spacings on the hips, at one end of the roof the hip and wall points will be on opposite sides of the creepers.
Also, if you select 'Exact Spacing', which adjusts both end ridge spacings to suit, it notes this in the running results, with these measurement points in bold.

Do the descriptions and 'alerts' in the results explain it clearly enough?

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Originally Posted by Blocklayer

Do the descriptions and 'alerts' in the results explain it clearly enough?

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I think so, but I got peculiar results on the example with 'Exact Spacing:' The ridge is listed as 6050 long, but has a tick at 6150 - beyond the end. Might be an arithmetic error in your formula.

Aside from that, for exposed framing, perfect alignment might look best. But framing accessories work best with a slight offset to prevent interference of fasteners from both sides. If the accessories have multiple fastener holes, that probably wouldn't matter.

Cheers,
Joe

Thanks for picking that up Joe. Fixed now.

Could you explain a little more about the 'slight offset' you mentioned?

"Blocklayer" - Mate you've done it again - great enhancement to an already great site! No doubt Joe will answer himself, but US timber frame construction varies quite a bit from what is done here so that's a 'gotcha' to just be aware of. Some things they do are better and ahead of us (in modularisation and time saving using fixings and tools especially) and others aren't. They do use timber much more - brick and brick veneer is uncommon although there are pockets where they are seen more. They are way ahead on good insulation practices.

We use a lot of framing accessories made of folded sheet metal to attach members in sequence. Google [simpson strong tie australia] indicates they're used in Oz too. If the fastener holes are anti-symmetric with respect to their opposite numbers, all is well; if not, a wee offset would prevent fasteners (longer than the half-thickness of the receiving member) from poking their partners on the other side. I suspect the manufacturers have considered this - at least I hope so. I haven't used them directly, but I'll want to check them out later today when I replenish some bandsaw blades. Thanks for jogging my curiosity.

Who's on first? Each of our countries are ahead of each other in many categories. Or something like that.

Cheers,
Joe

Unfortunately, some of my hopes were dashed.

I photographed 3 sets of framing accessories at Home Depot (a business model for Bunnings) to illustrate the problem of offset fastenings. The first and third pair employ outboard fastening flanges; the second pair has the flanges inboard of the meeting member. They're all arranged with the far side element on the far side of the main member, flipped about a vertical axis to represent its final position.

The first pair, US part LUS28Z, has symmetric fastening holes, requiring offset positioning. So does the third pair, US part H16S; this is very curious, because I think the smaller holes on this one could just as easily have been made in the same pattern on both flanges, so that the near and far holes would have escaped fastener interference.

Only the second fitting, US part LUC210Z, has the holes themselves offset vertically enough to prevent fastener interference.

These are three of many varieties, and products available in Australia may be different. Also, newer versions of these fittings may satisfy the dual objectives of uniform locations for the meeting members, and deliberate mis-alignment of the fasteners for better purchase in the supporting member.

All of this is part of a larger problem still awaiting resolution.

Cheers,
Joe

Originally Posted by joe greiner

We use a lot of framing accessories made of folded sheet metal to attach members in sequence. Google [simpson strong tie australia] indicates they're used in Oz too. If the fastener holes are anti-symmetric with respect to their opposite numbers, all is well; if not, a wee offset would prevent fasteners (longer than the half-thickness of the receiving member) from poking their partners on the other side. I suspect the manufacturers have considered this - at least I hope so. I haven't used them directly, but I'll want to check them out later today when I replenish some bandsaw blades. Thanks for jogging my curiosity.

Who's on first? Each of our countries are ahead of each other in many categories. Or something like that.

Cheers,
Joe

Joe - yep we use many of the same types - in Oz mostly by the major manufacturer under the Pryda brand http://www.pryda.com.au/ - actually a part of Illinois Tool Works Inc http://www.itw.com/.

I was not intending to be nationalistic or exclusive at all, but I have been to school, lived and worked in the USA, have long-time friends there and visit often, so really just making sure that forum members reading are aware there are differences. We get posts from the UK and elsewhere too - and although much is the same a lot is different too. It is easy to read a post without looking at the location of the poster and perhaps being led astray - just as often we re-open an old thread because the topic interests us now when the original might have been years ago!

As to the fasteners - most I have used have offsets in the pressed metal fittings so that no adjustment has to be made to the timber components. Makes sense, but that doesn't always factor in design!

Thanks for all that info Joe and Bloss. With all the math, geometry and adjustments in roof framing, it's a wonder any roofs come out anywhere near square

If you were using an offset, would you still mark each side (or top) to exact, and just add a small offset one side and subtract the same from the other? As in, could you still use the running measurements from the calculator?

And could/would you attach the brackets before you lifted and positioned the ridge?

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Originally Posted by Blocklayer

Thanks for all that info Joe and Bloss. With all the math, geometry and adjustments in roof framing, it's a wonder any roofs come out anywhere near square :

That's why most use trusses designed and cut by computer! And even then quite a few don't come out square - at least when they are put together!

Originally Posted by Blocklayer

If you were using an offset, would you still mark each side (or top) to exact, and just add a small offset one side and subtract the same from the other? As in, could you still use the running measurements from the calculator?:

As I said I would use the calculated measurements (in my case from my trusty old roofing square and roofing table book - I find the laptop awkward on the building site!!). I would were I building for money anymore that is!

Originally Posted by Blocklayer

And could/would you attach the brackets before you lifted and positioned the ridge?:

I've done both - depends a bit on how complicated is the roof and the ridge access etc. Mostly I do in situ work and install brackets as I go as that allows flexibility if things aren't quite what they are meant to be. If I have done the marking up and cutting out then would feel better about pre-fitting brackets. But I have had to re-jig too many truss components supposedly 'computer-perfect' to trust measurements of others. I know it will surprise you to hear it, but I too get it wrong occasionally!

Originally Posted by Blocklayer

Thanks for all that info Joe and Bloss. With all the math, geometry and adjustments in roof framing, it's a wonder any roofs come out anywhere near square

If you were using an offset, would you still mark each side (or top) to exact, and just add a small offset one side and subtract the same from the other? As in, could you still use the running measurements from the calculator?

And could/would you attach the brackets before you lifted and positioned the ridge?

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IF I were a chippy, I'd use the running measurements from the calculator to set out the centre lines of the meeting member on the receiving member. The amount of offset, if any, would depend on the fastening accessories in hand. I see you've specified the zero point for the hips as the upper end - good, because it's a better purchase point for a tape.

Like Bloss says, it depends; mostly on access, I reckon. Also, the level of production. In a factory situation, more complicated calculations would probably be developed anyway.

Cheers,
Joe

Originally Posted by Bloss

As I said I would use the calculated measurements (in my case from my trusty old roofing square and roofing table book - I find the laptop awkward on the building site!!)

What do you reckon about this for an idea:

I sort of thought, especially up on a roof or scaffolding, that the mobile versions of these calculators would be handy. If you have a (newer) internet enabled phone (like an iPhone), you'd have access to these calculations wherever you take your phone.

But the screens are tiny, and hard to read in daylight. So, just to experiment, I've added the running setout points to the mobile hip roof calculator, with buttons next to each run list. When clicked the measurements are displayed in HUGE font size, with Next and Previous buttons to step through the list.

The mobile site displays ok on a desktop browser, so you can see what I mean at http://blocklayer.mobi/Roof.aspx
(the Running Setout box is checked by default, so just click Calculate)

So, do you reckon this sort of thing could ever be handy?

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