Using extract to extend a BIAB brew length.

[Greendan]

So I've done a couple of BIAB brews. My hob can only handle boiling around 16 litres, giving me around 10.5 litres into the FV.
I'm wondering if I could add extract to the boil to up the gravity and then dilute it back down to around 20 litres? My BIAB og is around 1050 and I'd like to stay in that region. So if I used about 1kg dme would that be sufficient? Is my plan even on the right track? I assume I'd have to up the hops to balance the increased malt.

[Clibit]

Yes you can. You really want to use a brewing calculator like Brewmate, Beer Engine, Brewtoad, Beersmith, Brewersfriend, You can then calculate how much you need of everything to get the required OG and IBUs etc. Create a recipe for 20 litres, add grains and extract, and hop for 20 litres. I add the extract at the end of the boil.

[f00b4r]

You can also extend your brew length by using full volume variation methods (holding water back and adding after the mash and/or during the boil and/or sparging). If you grab a copy of the Biabacus you can get an idea of what your specific equipment would stretch to (it automatically calculates this for you). It will cost more in terms off grain/hops as your efficiency drops but not really any significant amount. The guys over at biabrewerminor will also sanity check for you to make sure you are not pushing things too far.

[Greendan]

Would adding the extract at the end of the boil affect the proteins in the wort? I thought boiling was important because of the "Hot Break". Or has that already occurred during the process to create the extract?

[f00b4r]

Would adding the extract at the end of the boil affect the proteins in the wort? I thought boiling was important because of the "Hot Break". Or has that already occurred during the process to create the extract?

It has already occurred during the extract creation process, hence why can kits just need mixing with hot water.