Ive customised the seatle master page in 2013 and set it as default in spd2013. This works fine for the current site collection. My question is how can i go about making this the default master page for any new site collections without having to upload the master page and style sheet to the master pages library and then setting as default in spd2013
You have multiple options:
- Provision a sitecollection -> create a new sitecollection template
- Create a stapling feature -> bind feature to an existing template
I would choose the stapling feature if it's only the masterpage that needs an update. If you need a lot more work done on the site, like creating fields, contenttypes, ... I would go for the provisioning.
(for a tutorial, see feature-stapling (this is SP2010, but it's almost the same)
I have not worked with SharePoint 2013 but in 2010 version you must turn on the Publishing feature for the Root site and in the Site Action -> Site Settings -> Master Pages you will see a screen like below: link