For a 2"x 1" batten which from the sheds will be 44mm x 19mm you will need 19mm + the length of the plug, around 32mm, so 50mm or 2". Follow KIAB's chart and in imperial you need a 8ga or a 10ga or in metric a 4mm or a 5mm with a red or brown plug. Personally I would use a 8ga/4mm screw with a red plug which requires a 6mm masonry drill. This is just my opinion. In this game you have to learn to convert between imperial and metric but it's a lot easier than plumbing sizes.
Gotta add with red plugs,5.5mm drill bit gives a lovely tight fit, depending on what wall is made from, plugs may need a tap in with a hammer Soft blocks, may even get away with 5mm bit Now.......... what type of countersink head should the screw have ..........Arghhhhhhhh .........
Just to be awkward I'm going to say use 65mm screws and Brown plugs so you have nearer 50mm in the wall, curtains are generally heavy.
I have two different size wall plugs but I don't know which one's to use. Brown 45mm and 30mm. Red 35mm and 28mm.
2x1 from the sheds is generally only 18/19 mm and a plug is 30/32mm so anything longer than that is sitting in a void but this is all personal preference. The screw is in sheer rather than tension so you are trying to snap the screw rather than pull it out, there is a little cantilever action but I'm sure KIAB has a chart to show the forces involved. All I can really say is this is how I do it and I've never had a failure.
Tend to agree, but I am not going to overrule an expert. The most important thing is to ensure the batten is pulled tight to the wall to eliminate any movement. It's the movement that will weaken it.
I did a little search tonight and whist not entirely scientific or directly compareable a M4 bolt to 8.8 has a shear of 7KN http://www.tech.plymouth.ac.uk/sme/desnotes/boltb.htm These are bolts not screws but it does show you how strong a thin bit of metal is in shear. 7KN is roughly 700KG
I doubt if a standard wood screw is anywhere near 8.8 in strength. This shows the USA figures in LBs. https://www.screwdoctor.com/application/home/selection_guide/technical_data.aspx
Just an aside. I'm not a builder, but an engineer and I have been told that you shouldn't use self cutting screws, ie, turbos,as they cut into the wall-plug, rather than expanding it.
That is exactly what Fischer will tell you and they know fixings better than anyone. Lemonade: just remember that a NoXX or XXGauge screw is imperial and XXmm is metric and they are not the same. Have you thought about using some basic frame or hammer fixings such as: http://www.screwfix.com/p/fischer-nylon-hammerfix-6-x-60mm-50-pack/28374 or http://www.screwfix.com/p/fischer-nylon-hammerfix-8-x-60mm-50-pack/20746 choose the preferred size. You drill and countersink the batten, put it in place and drill through a hole into the masonry, insert the fitting and tighten but not fully. Then, adjust the batten to get level, drill through another hole, insert fitting and repeat. There is less chance of the holes being misaligned or the batten sloping.