riven versus bandsawn for wooden shingles

[Random Orbital Bob]

Lets suppose I wanted to build a small lean to type building to house wood in stickered form outside and that structure would have a wooden shingles roof. Lets say oak because cedar is hard to come by and expensive whereas oak is more available.

Now of course riven timber will be stronger because the grain isn't cut down the length of the tile. And we know that the corollary is that bandsawing it will cut the grain tubes inevitably, and the resultant shingle will be weaker.

What I'd like to know is how much weaker? Specifically, if a riven oak shingle roof will last say 30 years, how much less might a sawn shingle roof last? (Assuming identical dimensions).

 

[lanemaux]

Something else to consider Bob is that in riven timber you present very nearly zero open end grain. This may lead to some warpage issues which , in single shingle (hey , that rhymes!) would be negligable , over the course of hundreds might get significant. Just a thought amigo , not based in previous experience .

 

[woodpig]

I would expect it's more about water absorbtion than strength. Riven shingles should shed rainwater better than sawn as well?

 

[SteveF]

Lets suppose I wanted to build a small lean to type building to house wood in stickered form outside and that structure would have a wooden shingles roof. Lets say oak because cedar is hard to come by and expensive whereas oak is more available.

Now of course riven timber will be stronger because the grain isn't cut down the length of the tile. And we know that the corollary is that bandsawing it will cut the grain tubes inevitably, and the resultant shingle will be weaker.

What I'd like to know is how much weaker? Specifically, if a riven oak shingle roof will last say 30 years, how much less might a sawn shingle roof last? (Assuming identical dimensions).

when did cedar become hard to get ?

my whole shed is made from cedar i couldnt afford oak

Steve

 

[Random Orbital Bob]

I'm saying nothing other than that I own a large chainsaw and live in a rural location!

There are many oak trees (fallen) where I live and no cedar!

Individual church goers can draw their own conclusions from that.
But back to the original question...I don't mean strength, I mean roof longevity ie will it last "enough" time even if bandsawn....say 10 years?

 

[SteveF]

that makes sense
it did prompt me to read this
and look at the scary pictures

http://blog.lostartpress.com/2014/04/18 ... -shingles/

Steve

 

[Jacob]

As far as I know riven is best but if you google you find both are widely available.
Here is one site picked at random http://www.silvatimber.co.uk/shingles-s ... ngles.html
Oak is nowhere near as durable as western red cedar and isn't used a lot except on porches, lych gates etc, where maintenance is easy.

 

[RobinBHM]

I think cedar shingles are sawn rather than riven which are cedar shakes. The shingles Ive seen have almostn perfectly straight grain so even if its sawn, it must be carefully selected.

Im not sure if the grain of oak would be straight enough yield good shingles and free of knots. Oak can be prone to surface checking that may cause a problem as well.

http://tealjones.com/our-products/red-c ... cedar-cam/

This is a modern factory in canada, but doesnt seem very safe practice -is the guy wearing a chain mail glove maybe?

 

[paulm]

Interesting question Rob. Based on the lifespan of the average untreated oak bench or seat, and although the shingles would be of thinner cross-section, I would be hopeful of them lasting a good many years, particularly if used at a decent angle to help shed rainwater ?

Cheers, Paul

 

[Random Orbital Bob]

That's my thought too Paul. I just wanted to bounce it off the forum. I might even treat said sawn shingles (shakes) with clear cuprinol as a belt n braces approach for the end grain.

I reckon if it lasts 10 years its done its job.

 

[Sgian Dubh]

... riven timber will be stronger because the grain isn't cut down the length of the tile.

What I'd like to know is how much weaker? Specifically, if a riven oak shingle roof will last say 30 years, how much less might a sawn shingle roof last? (Assuming identical dimensions).

A 25 mm (1”) thick riven oak board is as strong as a sawn board 50 mm (2”) thick. You could estimate strength characteristics from that information if you know the typical strength characteristics of oak*, and have the formulae to hand to do some calculations. Knowing the strength of a riven oak shingle doesn't help with durability, it being primarily the ability to endure when in contact with soil, and to a lesser extent when exposed to the elements, because durability has very little to do with strength or hardness. But thicker will generally last longer than thinner simply because there's more wood to rot away. Slainte.

* European oak modulus of rupture: 97 MPa.
* European oak modulus of elasticity: 12,500 MPa.

 

[woodfarmer]

I am interested how you would split them? I split a lot of oak to make short planks for kindling. For this job I use my log splitter. Green wood is easiest. chainsaw the rounds to length selecting straight grained bits for planks. The rest goes as firewood lumps or bowl blanks

 

[Random Orbital Bob]

... riven timber will be stronger because the grain isn't cut down the length of the tile.

What I'd like to know is how much weaker? Specifically, if a riven oak shingle roof will last say 30 years, how much less might a sawn shingle roof last? (Assuming identical dimensions).

A 25 mm (1”) thick riven oak board is as strong as a sawn board 50 mm (2”) thick. You could estimate strength characteristics from that information if you know the typical strength characteristics of oak*, and have the formulae to hand to do some calculations. Knowing the strength of a riven oak shingle doesn't help with durability, it being primarily the ability to endure when in contact with soil, and to a lesser extent when exposed to the elements, because durability has very little to do with strength or hardness. But thicker will generally last longer than thinner simply because there's more wood to rot away. Slainte.

* European oak modulus of rupture: 97 MPa.
* European oak modulus of elasticity: 12,500 MPa.

Thanks Richard.

 

[Random Orbital Bob]

I am interested how you would split them? I split a lot of oak to make short planks for kindling. For this job I use my log splitter. Green wood is easiest. chainsaw the rounds to length selecting straight grained bits for planks. The rest goes as firewood lumps or bowl blanks

The idea is to use a froe Larry. You're right about the need for very straight grained timber because it splits evenly then.

 

[Sgian Dubh]

The idea is to use a froe Larry. You're right about the need for very straight grained timber because it splits evenly then.

It's always easier to split most wood species radially (but especially oaks) following the lines of weakness inherent in the radially orientated medulla, although I assume you know that already.

It's reckoned by some that one factor leading to oak's historical popularity as a wood to build things with was the ease with which it could be cleaved or riven back in those times when sawing technology wasn't developed enough to convert logs into boards successfully. In Europe (it's been reckoned) that nothing was converted into boards using saws until at least the 11th century. I suppose it's possible that other cultures in other continents may have had such technology available to them earlier, but I'm not aware of anything that indicates this. Slainte.

 

[Random Orbital Bob]

I would concur with that from a practical point of view too. Oak is an absolute joy when hand riven radially and its truly amazing how even you can get a slice off it. In fact, it splits so easily it almost belies how dense and strong it normally feels in other applications. When riving it seems almost brittle.

 

[RobinBHM]

Maybe an electric log splitter could be used for the splits, although I dont know how controllable they are.

Certainly oak is quite weak in shear, judging by those irritating bits that flick up and wont stick back down well.

 

[owenmcc]

http://www.spab.org.uk/advice/technical-q-as/technical-q-a-35-shingles/

This quote might be of particular interest: "Riven oak or chestnut shingles normally have a lifespan of 80-100 years, which can be twice that of those made from cedar." Might make those hard hours of hand splitting worthwhile.

I've done a few 'shingle' roofs with imported cedar of the 'handsplit and resawn shake' variety which basically means split/riven on one side and bandsawn on the other. Very easy to lay, with the consistency of the machined surface and then the look and drainage benefits of the traditional. Both were laid within the last few years, so I can't offer a concrete answer to longevity (min. two Scottish winters!)

As ever some great things on popular video site:
Traditional: https://www.youtube.com/watch?v=NZreNpDlRQ4
Resawn: https://www.youtube.com/watch?v=ahZz1E1GFsk

Should be a fun project, whichever way you go about it.

 

[Random Orbital Bob]

Interesting...thanks chaps.

 

[Random Orbital Bob]

So for arguments sake lets say I've settled on the notion that band sawn shingles are sufficiently long lived to choose that option over riving them. After all I'm only talking of a lean to roof against a brick wall that can house air drying timber, turning blanks etc to get them out of the garage.

It will be oak that's used (and green at that). What thickness should I go for? My minds eye keeps alighting on 1/2" for some reason though I've done no research on this. I'm thinking too thin and they'll be likely to split etc, too thick and they'll be difficult to lay. 1/2" seemed a sensible compromise but it's entirely possible I'm talking out my ...