Diagonal Bracing

[Boulder Block]

Hi everybody! I've enjoyed lurking here for a while but now I'm ready to add a question. I'm about to re-clad a very old tin roof. The section I'm working on is the steep-pitched part of an old miner's hut, it's above the two main rooms that made up the original house.

I'm all set to do the job but I've noted a lack of bracing. At either end of this roof there are gables with queen posts, everything else has no kind of bracing between the top and bottom chords. There is one timber diagonal brace running from one end of the roof to the other. So a few questions arise:

Is this adequate?

Would there have only ever been one diagonal brace?

If bracing needs to be improved would it make sense to add something like strapping or speedbrace for diagonal bracing at this re-cladding stage, rather than timber inside the roof later?

About the roof:
1919 Miner's Hut
100 year old jarrah framing
Wind Class - N1
Span - 3.77m
Length - ~8m
Pitch - 40 degrees
3ft between 1 3/4" thick rafters

If this is a bit too specific and technical for a forum, does anyone know where I could get some advice? I'd be especially interested in advice specific to old homes.

I'm looking at buying the NCC volume 2, but I'm not sure I'll get the answers I need out of it anyway.

[rambunctious]

Is what you have adequate ?, yes, by the standards of yesteryear but not by today's standards, which seem to change at the whim of the public service (govmint)
And fwiw I have not looked at standards in a lot of years.
Strap it for your own peace of mind.
But be warned, at some point while screwing the roof you will hit the strap and have fun getting the screw through.
Best to drill a hole in the strap (should you be so unlucky to hit it) to get the screw through.
Hope you are using an insulation blanket under the sheets, well worth it.

[r3nov8or]

Yes, you should add bracing. It's cheap insurance. It needs to be attached to rafters, so run it under the battens and you won't have any hassle hitting it with roofing screws. You may need to lift the batten where it crosses a rafter here and there, but choose a run which minimises that hassle. Fix the brace at each rafter crossing.

[Boulder Block]

Thanks for the advice guys. Yes, I will be adding some insulation to bring that up to scratch. Also yes, I would be putting the bracing under the battens, since I need to replace the battens anyway, some are pretty tired. Cheers!

[jack620]

I would be putting the bracing under the battens, since I need to replace the battens anyway…

In that case I’d be using speedbrace. Just a moment...

[Boulder Block]

Yes, I was looking at a different brand of the same thing. I'd have to get whatever the local building place stocks, Bunnings don't stock anything suitable here.

[ian]

Boulder Block
A number of questions for you:

is the 1919 miner's hut heritage listed?

do you have a requirement to bring the roof of the building up to the current building code?
If yes, it would pay to know what the current code requirements for the roof are before you begin working on it.

will the building you are working on be insured for risks that a roof not up to code would result in the insurance being voided?

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Yeah, I know PITA type questions

[Boulder Block]

Thank you for the PITA questions Ian, they are the exact sorts of things I've been thinking about.


No heritage listing on this property. I've recently discovered it's probably a fair bit older than 1919, but there are so many old properties in our charming time-capsule of a town the heritage folk are spoiled for choice and this example is not flash.


What I want to achieve is to replace old roofing iron with Colourbond (it's so old some of it is literally iron, not steel). I've read the following and it's pretty straightforward:


https://www.commerce.wa.gov.au/sites...er_web_0_1.pdf


https://www.commerce.wa.gov.au/sites...adding_1_0.pdf


What is less clear to me is what my opportunities might be at this stage to improve things to prevent future problems.

So to answer the question, no I don't have any particular reason to bring the roof up to code. Only the new covering has to be installed to current standards.



My overall goal for the house is improvement, not perfection. She's a very cheap house that has already been vandalized by previous owners (and squatters on meth!). Some of it I can undo, some of it I'll have to put up with, and some of it I'm unsure about.

[ian]

Thank you for the PITA questions Ian, they are the exact sorts of things I've been thinking about.

No heritage listing on this property. I've recently discovered it's probably a fair bit older than 1919, but there are so many old properties in our charming time-capsule of a town the heritage folk are spoiled for choice and this example is not flash.

What I want to achieve is to replace old roofing iron with Colourbond (it's so old some of it is literally iron, not steel).

given that steel making was industrialised in the 1860s, I would be more than most surprised if the original "wriggly tin" roofing was NOT originally galvanised steel.

I've read the following and it's pretty straightforward:

https://www.commerce.wa.gov.au/sites...er_web_0_1.pdf

What is less clear to me is what my opportunities might be at this stage to improve things to prevent future problems.

So to answer the question, no I don't have any particular reason to bring the roof up to code. Only the new covering has to be installed to current standards.

as I read that "changing your roof cover reference, what you must do with the old building is
1. ensure the roof is tied down to the building frame in accordance with the requirements of the current building codes, and
2. ensure the building frame is properly tied down to the building's foundations in accordance with the requirements of the current building codes. Doing the later might require the construction of new foundations, or the driving of ground anchors strong enough to resist the building being plucked off its foundations in code specified winds.

[jack620]

Doing the later might require the construction of new foundations, or the driving of ground anchors strong enough to resist the building being plucked off its foundations in code specified winds.

As if anyone is going to do that for a resheet of the roof of a 100+ year old miner’s hut.

[Boulder Block]

I see things like straps tying rafters down, and I'm unsure how old they are. There has been a time where some professional-looking roof replacement has been done on a portion of the roof, so it's possible there were some upgrades then. That's the sort of thing I need an engineer/builder to have a look at in person. It's also another reason why I don't want to change anything like weight, pitch, profile, etc.
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There is quite a story behind the wriggly tin, if you are interested...

I went to see the council to find any information about my house. They had 1919 as a date for the building and nothing else. The councils of Kalgoorlie and Boulder amalgamated in 1989, and they lost all the records for Boulder in the process. I've since found the original homeowners advertised a boarding situation at that address in a 1901 newspaper. With that, and other observations, I think the original home was two-rooms (and a verandah or two) built between 1899-1901, and had an iron roof and hessian walls, like many at the time. I think 1919 could have been the year it was clad with fibro and extended.

The oldest-looking iron on the roof has a Redcliffe trademark on it. A researcher who has written about the history of the brand has identified different versions of the trademark stamp. The version on my roof corresponds to corrugated iron manufactured between 1881-1895 at the Redcliffe Crown Corrugated Iron Company in Bristol. This company sourced its materials from iron mills with the same owner.

The owner of these companies, Joseph Tinn, was focused on expansion by buying up and leasing old iron mills in spite of the impact of emerging steel technology. From 1893-1895 there was a depression, and at the same time, 1884-1885, the sheet trade transitioned to steel. Without enough capital left to modernize he was forced to file for bankruptcy in 1895. When assets were sold off, only the goodwill and trademark of Redcliffe was purchased by John Lysaght Ltd. in 1895. They had no interest in buying any of the physical assets since they were old ironworks, and they'd already invested in a state-of-the-art facility at Newport, which opened that year. They manufactured corrugated sheeting, marketing Orb as the premium, and Redcliffe Crown as the economical second choice. Although the newer product is a different one the Redcliffe stamp they used looks very similar to the old ones, so it looks like the same thing at first glance.

If anyone is interested in the paper I got all the information from it's available to download here:
Just a moment...

[ian]

as I read that "changing your roof cover reference, what you must do with the old building is
1. ensure the roof is tied down to the building frame in accordance with the requirements of the current building codes, and
2. ensure the building frame is properly tied down to the building's foundations in accordance with the requirements of the current building codes. Doing the later might require the construction of new foundations, or the driving of ground anchors strong enough to resist the building being plucked off its foundations in code specified winds.

As if anyone is going to do that for a resheet of the roof of a 100+ year old miner’s hut.

Boulder Block essentially asked what he needs to do to when replacing the sheeting on his miner's cottage.
The reference BB supplied requires that when replacing the roof material, the person doing the resheeting must ensure that the roof structure (rafters and such) is tied to the building frame in accordance with the current building code.

My recollection is that the current building code (post 2020) require that not only the roof structure be tied down to the building's frame, but the building fame itself be tied down to the building's foundations [and that the foundations themselves be structurally sound].
This requirement -- tying down to a structurally sound foundation -- is to prevent the building being lifted off its foundations in the design wind.
Doing this later bit, tying down to the foundation, often requires a number of ground anchors be installed.


The difficulty of doing all that is a major reason why old buildings like Boulder Block's miner's hut typically fall down through neglect or are demolished rather than restored.

[ian]

I see things like straps tying rafters down, and I'm unsure how old they are. There has been a time where some professional-looking roof replacement has been done on a portion of the roof, so it's possible there were some upgrades then. That's the sort of thing I need an engineer/builder to have a look at in person. It's also another reason why I don't want to change anything like weight, pitch, profile, etc.

good thinking.

[jack620]

My recollection is that the current building code (post 2020) require that not only the roof structure be tied down to the building's frame, but the building fame itself be tied down to the building's foundations [and that the foundations themselves be structurally sound].

That's not just a requirement of the current edition of the National Construction Code, it was required in the old BCA for decades. That's not in dispute.

Doing this later bit, tying down to the foundation, often requires a number of ground anchors be installed.

My reading of the documents Boulder linked is you are only required to obtain a building permit and upgrade the roof tie-down (in WA) if you are changing the type of roof cladding. Replacing metal with metal should not require this. A call to the local planning authority will clarify that. Of course, it would be prudent to upgrade the tie-downs where feasible, but with a metal-for-metal replacement, I don't believe it's a requirement.

[r3nov8or]

My reading of the documents Boulder linked is you are only required to obtain a building permit and upgrade the roof tie-down (in WA) if you are changing the type of roof cladding. Replacing metal with metal should not require this. A call to the local planning authority will clarify that. Of course, it would be prudent to upgrade the tie-downs where feasible, but with a metal-for-metal replacement, I don't believe it's a requirement.

The documents also says...

Even if you are replacing an aged roof covering with a like-for-like material, it is important to check the roof condition.

Need to remember that the metal sheet today is thinner, so lighter, than what it is replacing, and the screws, will provide far better hold than (presumably) the original capped nails, all leading to a greater possibly of losing the whole roof, rather than a sheet or two. The tie down starts at the battens, which may simply have been skewed nails in the old days.