Adding a 2nd brood box

[enrico]

or often, especially if the original brood box is well filled - they will ignore it and swarm rather than work down and draw it out.

I would suggest that is pure coincidence. They were going to swarm anyway. They normally build comb down for brood so why would that trigger a swarm?
Moving a couple of frames as suggested by Eric B will help if you feel you need to

 

[jenkinsbrynmair]

I would suggest that is pure coincidence

I would maintain it's not - as many others seem to agree, you are talking of bees having to skip down over a beespace gap (plus what they've already chewed off the bottom bar) to a lower frame then draw comb in the coldest spot in the hive - not extend a comb downwards, whilst already overcrowded, I've seen it happen in colonies that are not overcrowded, they still go.

 

[enrico]

I would maintain it's not - as many others seem to agree, you are talking of bees having to skip down over a beespace gap (plus what they've already chewed off the bottom bar) to a lower frame then draw comb in the coldest spot in the hive - not extend a comb downwards, whilst already overcrowded, I've seen it happen in colonies that are not overcrowded, they still go.

fair comment. I never have!

 

[SWEET]

I always add the second box on top, if the original box is rammed you're too late anyway and they will swarm (you can create as much space as you like in the original box and they still swarm anyway (but will delay them for a bit though)). I've found the best way is moving a couple of sealed brood/open into the new top box and add the second box when into 5/6 frames of sealed brood. Regards new box filling with honey, just move them into a super above and they soon fill the second box with brood. You do need to use one size box though, not for everyone. PH is right regards Q-cells in bottom box but it's rare so have to ponder time v's risk, reading the state of the top frames will give you clear clues on hive state most of the time anyway. Slim queen/no eggs etc etc.

 

[Ian Morton]

It's an option that converts nest shape from a pumpkin to a rugby ball and achieves the aim to expand the nest in both directions.

First time I put another box of foundation on top they filled it with honey; now I transfer three or four frames of open brood upstairs, close up combs below and add foundation or comb either side in both boxes. Add a super to make sure nectar goes above the broods. This works with multiple brood boxes; thirds can be put in-between the first two.

Not tried putting a new box underneath, but I imagine it would be drawn and filled more slowly as temps are lower, and comb may not be made quickly enough to avert congestion; a solid floor may speed up work.

Thank you Eric. Exactly the question I needed answering, having never used doble brood before. Just shows that it pay to search this website for the answers to simple question before bothering anyone else. Will pop out this afternoon and do precisely this.