# Forum Home Renovation Pergolas, Gazebos, Strombellas & Rotundas  Coach Screws/Batten Screws vs Coach Bolts???

## chalkyt

Hi All
The Hexagonal Gazebo project is underway again after a delay waiting for earthworks. 
I would like some opinions regarding using coachscrews/batten screws vs cuphead bolts for fixing beams to posts. The builder that helped with our house extension was a great user of long batten screws, particularly when fastening a long laminated beam into place. Unfortunately he has left the district and gone interstate so I can't pick his brains.  
The tops of the posts will be chamfered/checked out at 30 degrees, down 190 from the top to take 190 beams so the beams are partly supported by the remaining "triangle" where the post goes back to square. The 30 degree face that the posts are fastened to ends up at about 190x50. 
The easiset way to fasten the beams to the posts is by several batten screws or coach screws (say M10 or M12). More conventionally (especially with a square structure) you would simply through bolt. However with the 30 degree angle, where the bolts come through the back of the post, it will be necessary to counterdrill a washer recess at 30 degrees so that the head of the bolt and the washer/nut are parallel. This in turn requires some fairly accurate drilling both horizontally and at 30 degrees... not impossible but a bit of a pain. The back of the post also probably ends up looking a bit ugly. 
So, using batten screws or coach screws means that the drilling can be a little bit "off" and no one will notice since the screws won't come through the back of the post. 
Any thoughts?

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## phild01

IMO, I have found batten screws seem to use a stronger steel than coach screws but a single M12 coach screw would be stronger than a single batten screw.  I reckon two batten screws to be better than a single coach screw but have not seen any technical data on any of this.  Bolting would always be my first choice.

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## barney118

I'd use S/S batens, especially if going into TP. I pulled apart a deck with bolts and screws and there wasn't much left of either after 6 yrs.  
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## Moondog55

Barney what about the new epoxy coated TP bolts and bugles?
Chalkt I asked this question of ITW last week and I'm still waiting on a reply

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## barney118

Moondog I don't know about them, but when you see what TP does to hot dipped gal bolts I couldn't imagine a coating of epoxy would do much, I'd rather pay more for S/S  
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## Moondog55

I hope they are much better as I just used the gold bolts and Bugles in the new roof structure. Supposed to be epoxy over the gal

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## phild01

> I hope they are much better as I just used the gold bolts and Bugles in the new roof structure. Supposed to be epoxy over the gal

  Don't know the gold epoxy (hope they are not the gold zinc pacv ones), but the other type for treated pine look green to me.

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## Moondog55

I think they look green too;  but "gold" is  what the salesman at Bunnys called them

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## Micky013

Its surprising how much holding power a few bugles have. I think the advantage over coach bolts is the fact you can drive them in without a pilot hole hence greater grip.

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## phild01

> Its surprising how much holding power a few bugles have. I think the advantage over coach bolts is the fact you can drive them in without a pilot hole hence greater grip.

  For batten screws I use a pilot hole, don't like overstressing the grain.

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## Micky013

We go straight in. Even on the ends the timber rarely splits but each to their own.

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## chalkyt

A lot of the above comments relate to things that have been rattling around in my brain. I guess that conventional wisdom suggests through bolting everything but I wondered if experienced builders have found that the holding power etc of batten/coach type screws is just as good. Although our area is rated N2 for winds, we do get the occasional "damaging winds" warning so I have been working on the basis of N3. On the basis of caution, I will probably go the through bolt route if I can't get any information to the contrary (but batten/coach screws has its appeal). 
I have been using Timber Queensland Technical Data Sheet 19 (Pergolas and Carports) for guidance. This has some excellent stuff on spans, connection methods etc. Timber.net.au also has two very good documents on timber joint design and suggests that many small connectors is better than few large ones (i.e perhaps four batten screws or coach bolts rather than two through bolts). There is a fair bit of technical stuff on loads, stresses etc in their publications but I really haven't delved into it.  
However, I imagine that such publications are often conservative and sometimes not up with improved methods that experienced building tradesmen are currently using especially as new products come along. Anyhow there is so much knowledge and wisdom rattling around the forum, I thought it was worth throwing the question out there. 
Like many others, when TP came on the market (1980ish???) I saw it as the solution to everything and so did some work around my place using zinc plated screws/bolts... didn't last long did they. The green TP fasteners hit the market and seemed to be a bit better, then gal became the answer... but I agree, if you take them out after a couple of years, signs of some deterioration do appear to be there. Not sure about the new "yellow" stuff. I have seen it but not used it.

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## Moondog55

I'm still waiting for my answer to these questions from ITW
But I'm thinking that a lot of it depends on the direction of the forces. Obviously the shear strength of a #14 bugle is greater than a standard 90mm nail because of the increase in shank diameter but is the pull-out resistance of a single #14 batten screw superior to two 90mm skew nails?
I just butt joined two 190*45s using 4 X 90mm bugles but also added a corner bracket using 6 X 10mm coach bolts on the inside because I felt that a direct force in line with the bugles would simply pull the small heads straight thru the timber, but perfectly strong enough in shear 
@ micky013: I think it depends on the timber. I have to pre-drill 90% of my holes for bugles as they will not drive into the old hardwood without splitting it unless I do that, it also save the battery in the percussion driver

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## Micky013

Agree 100%. Pine we go straight in. On the weekend i sistered some jarah joists (both ends supported) but bugled together. I had to pre drill as there was no way they were going in. Lately at work we have bugled a lot of porticos to posts - whether its better i dont know

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## intertd6

All the information you require is contained within the tables of AS1684, tables 9.2 I believe.
regards inter

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## chalkyt

Thanks for that. As we don't have a suitable library nearby I had been holding off spending yet another $100+ for a standard that I will probably only use once (and then only 10% of the information therein). However for "belt, braces and safetypins" peace of mind, I will probably go down that path and buy AS1684. It is a shame Standards Australia don't have an el-cheapo lookup service for occasions like this.

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## intertd6

> Thanks for that. As we don't have a suitable library nearby I had been holding off spending yet another $100+ for a standard that I will probably only use once (and then only 10% of the information therein). However for "belt, braces and safetypins" peace of mind, I will probably go down that path and buy AS1684. It is a shame Standards Australia don't have an el-cheapo lookup service for occasions like this.

  i wouldn't be paying for it, it can be found on the net at various times, links have been provided on somewhere in this forum.
regards inter

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## Moondog55

Found it with some help from the technical department  http://www.buildex.com.au/pdf/techni.../03125-PDS.pdf

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## chalkyt

Thanks for the advice. I have acquired a copy of AS1684.4 but it doesn't seem to help. Section 9 seems to deal mostly with nails and strapping. Moondog, good info from Buildex, it does seem as though batten screws are being used in all sorts of applications but nowhere can I find anything like "three batten screws equals one M12 coach screw" or something like that.

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## Moondog55

> Thanks for the advice. I have acquired a copy of AS1684.4 but it doesn't seem to help. Section 9 seems to deal mostly with nails and strapping. Moondog, good info from Buildex, it does seem as though batten screws are being used in all sorts of applications but nowhere can I find anything like "three batten screws equals one M12 coach screw" or something like that.

  No; for that information you need to do the comparison yourself and as most bolts are simple mild steel I'm still trying to find out myself. My supposition is that equal cross sectional areas should be equivalent but that is a very simplistic view on my part.
So 2 * #14 bugles should be equal to 1 * 12mm mild steel bolt but I wouldn't bet on it. And of course that is only for single shear, pull-out strength is more complicated

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## phild01

> No; for that information you need to do the comparison yourself and as most bolts are simple mild steel I'm still trying to find out myself. My supposition is that equal cross sectional areas should be equivalent but that is a very simplistic view on my part.
> So 2 * #14 bugles should be equal to 1 * 12mm mild steel bolt but I wouldn't bet on it. And of course that is only for single shear, pull-out strength is more complicated

  I am pretty sure you can depend on reliable higher strength steel from a batten screw than that of a coach screw.

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