It may seem like a numpty question, but I’m looking to build a bike with Alfine gears and I’m wondering what drop outs I would need?

Does it have to be a single speed frame?

The plan was to get an old road frame and build it into a commuter/quick nip down the shops type bike

Also, if I get an old frame, will I have problems with fitting new headsets and chainsets etc?

Alfine will work in horiz or vert dropouts, you just need the right no-turn washers. Different colours for different setups.

you will need some way of tensioning the chain

The Alfine works with all/ dropouts, as bri-72 said, it just uses different ‘no turn’ washers – these prevent the axel from turning and come as part of the fitting kit.
There are blue/green ones for virtical dropouts and,iirc,grey/white ones for horizontal and i think theres another couple of colours, yellow and silver?for other dropouts.
The Alfine will work in ‘standard’ frames with a chain tensioner – or idealy in a frame with some sort of inbuilt tensioner, horizontal dropouts, EBB, Slot dropouts etc.

You can use either drop-outs, but need to consider how you’ll tension the chain. They make a tensioner if you need it.

You’ll more likely have trouble finding forks than a headset, so it would probably be worth sticking with 1 1/8″ headset and fork steerer tube.

Chainset will depend on what bottom bracket type you decide to use.

take a look at this page from sheldon: the font of all bicycle knowledge, scroll down to the dropout pics. you can use anything that looks like the horizontal dropouts, anything that looks like the ‘stamped dropouts’ of any kind, or the trackend. you can also use a sliding dropout system, or a eccentric bottom bracket for tensioning, but no ‘old road frames’ are likely to come with they.
otherwise you get in to tensioner territory.
HTH.
edit, also you have to consider OLD ( look it up on sheldon ), but mostly a steel frame will cope, unless using proper track stuff, in which case the spread for an alfine might be asking a bit much…

As above the 135mm oln of an Alfine may be hard work with an old steel frame. Plus an old roadie won’t have disc mounts which may mean you would be better with a nexus hub. Or even better do what I did and use a 3 speed sturmey archer if it’s just your nip to the shops bike.

If you really want the Alfine you can make your life a lot easier by getting a kaffenback, pompetamine, roadrat etc frame.

Thanks for the help

I just have it in my mind to build something old and classic looking, maybe getting the frame painted or powder coated, and get some chrome bits, bars rims etc

The alfine idea is because its far too hilly around here for a single speed to be practical, and I want to keep it as clean looking as possible