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Condensation causing large gaps


Hi @Stu_Anderson and thanks for your input, I’ve rebated the door and set a small piece of wood in place to close the gap but hopefully when I’ve resolved the condensation issue the gap should reduce as it was not there when I first built my hive. I’ve removed the foam now so the bees will be able to access the clean up area :+1:

I’ve removed the key slot caps as you suggest to help dry everything out but I’m not convinced my roof is leaking but I’m going to dismantle it and seal all joins just to eliminate that.
I’m due to check another one of my hives and the weather has just changed for the better so while I’m suited up I’ll open the Flowhive to check the strips you mention.
Thanks again for showing an interest and thanks for a great product.


As you can see I have removed the roof and there is indeed cracks where water could be getting in.

I also checked the packing strips and as you can see they are in place in all four corners.
This picture show (I hope) how wet the loft space is.

While the roof is off and I’m sealing the gaps I’m going to drill two holes in the apex of the loft as someone suggested.


Well thank heavens. While we were all yakking about insulation and ventilation the roof was leaking. A case of not seeing the wood for the trees.


Let’s not count our chickens Dee lol, the water/condensation did not seem to coincide with rain fall but I stand to be corrected. I have now done a lot of modifications, sealed all gaps, which may just shrink when it all dries out, added ventilation, rebated the door and added the wooden strip , fingers crossed and thanks for all the support.


I really hope it works. Maybe put on a regular flat roof?


Let’s put a few myths about condensation and ventilation to rest…

Q. What causes condensation?
A. High humidity air coming into contact with a cooler surface.

This is caused by the air temperature inside the hive being warmer than the surface temperature of the hive walls and roof.
Ok, how do we prevent it?
Two methods.

  1. Warm up the hive walls and roof to nearer the temperature of the internal air.
  2. Cool down the internal air to nearer the temperature of the walls and roof.

You do (1) by insulating the roof and closing off top ventilation.
You do (2) by adding top ventilation.
Both work to reduce condensation, but (1) results in a higher average internal hive temperature than (2).

For proper development of the brood, the bees need to keep the nest at a temperature between 32C and 35C.
Brood development may be total of a day or so shorter with warmer hive temperatures.

The slightly shorter cell occupation time for a developing bee has benefits for both decreasing varroa mite population AND increasing worker bee population, the female varroa not being able to produce as many offspring for each generation during the shorter capped pupal phase of the bee, and the bees having a quicker turnover of brood cells with the shorter development time. Bees raised in a warmer hive are also healthier and live longer.
(If a worker bee life is increased by just one day, then that’s a 2% increase in the work able to be done.)
The numbers might be low percentages in each case, but the advantages are exponential over a season and are there to be taken.




Dave…that looks really shaded to me. Are they getting morning sun and the afternoon sun being blocked? My mentor told us in our last meeting that with our high humidity the bees would need morning shade and afternoon sun…I would have to read back to see where you are located but I can tell you, here in Alabama the humidity has been tough!


Well, i have a problem with condensation and now mould, but not AFB or EFB. I am in Norther NSW, Australia, near Tweed Heads. I have a flat roof and have noticed condensation inside the hive, on the end of the frames and in the lid for some months, maybe. I’ve not done anything about it on the assumption that the bees would open and close the vents as needed. There were propolised closed. Now, the outside end frames are covered with what appears to be a black mould and all the other frames have ‘creeping’ mould.

I think my bees swarmed very early in August. Friends and I checked the brood last weekend, and all appears okay.

We’ve been in a drought for most of this year and water is not getting in from the roof, the endgrains of the flow hive are showing signs of water damage from rain last year, and i plan to swap out the flow box all together and sand 'n seal it again.

However it’s been so dry and I cannot understand this black mould or the continuous condensation. Any clues on what to do.



Since being on the forum & reading about condensation & mould, I’ve observed that the colonies with strong populations get very little condensation & no mould.

Anything that is completely covered in bees stays mould free. Anything that is void of bees eventually gets mould on it.


In agree Jeff my temp/humidity probes show the bees are able to regulate humidity between 50-70% when there is enough of them. When you have low bee numbers like an empty flow super in winter the humidity goes well above that and can reach 100%. If not full of bees take the super off.


Hi Jeff, well I now realise that the brood may have been a little chilly a over winter and even during late summer and I may have taken too much honey from the flow super. This combination may have stressed the bees. While our climate is warm, we live in a hollow and it is cool at night.

Unfortunately, I 've had to take off the flow super and put in a standard super. I’ve also changed over the bottom board and lid for a clean. I could never put the corflute on the top position in part because the bees were always hanging low in the brood, perhaps they were trying to block out the cold night air… I’ve now put the corflute in the top position and reduced the entrance by 50%. I thought I had a strong population, but obviously not. It’s not warm here overnight until December, so I’ll open the entrance then, and in January, move the corflute into the lower position.

So, the plan is let the bees populate the hive and make loads of honey in the standard super, and I have no idea as to when I will be able to put the Flow super back on. I certainly don’t want this happening again.


Hi Caterina, I don’t believe that removing the honey would have made any difference at all. It’s the lack of worker bees in the hive that would contribute to the mold & condensation.

I would leave the core flute in the top slot permanently. I’d also keep the entrance reduced to 50% during summer, however I’d place the reducer in the middle so that you have 2 smaller entrances. You could make them smaller during winter. In fact you could make them smaller now, while the colony is weak.

Your standard super will probably suffer the same fate if you put it on too soon. Wait until your colony numbers have greatly increased before adding the frames.

This is what I do, I place a hive mat, with an all around gap over the brood frames, with an empty honey super on top. Once the bee population starts to spill into the second super, I start adding frames after adding the QX.


Interesting comment Jeff. It appears that brood management is a delicate balancing act. A hive mat is a good idea. What can i use as a hive mat? I’ve read somewhere that lino will do the job, what do you think? I am sure i could buy them somewhere but it will take days for it to get here. It seems that I’ve underestimate the number of bees needed to keep a healthy hive, i’ve been focused on swarming as the biggest risk and understanding it. I don’t really want too many hives, two or three only.


Lino is a good option for a hive mat as is a piece of thin ply wood. JeffH has given you very good advice. You can bank on his information.


Hi Caterina, I don’t think you can buy them. Like Peter said, a bit of lino is all that’s needed. You can get some cheap lino from a carpet shop. One bloke gave us a roll end for free, so we took back some honey. He was pleased with that. Another carpet shop gave us enough for around 80 hives for $20.


Thanks. I’ll find some this afternoon and put it on first thing in the morn. Should I also take the QE out. It’s quite harmless (isn’t it?). I have a laying queen and there is comb and eggs on all eight frames.

I should say that my one 'n only nuc, which is in a small box with a flow hive lid flat inner lid and peeked roof is doing just fine.


I think I would leave the QX off for the time being. Make sure there is a gap all around the mat, so that the bees are able to spill over into the empty box. Also so that the bees include the empty box as available space to expand into.

When the nights start getting warmer & the bees are more populous, you can move two brood frames into the empty box & replace them with fresh foundation frames. In that case I’ll leave the QX off until the top box is 1/2 full of bees. I’d place those 2 frames together in the middle, flanked by fresh foundation frames.


I am resistant to removing the QE. I would like to keep the queen in the brood. I feel fine about the matt thingo although if the super is still on won’t the temperature difference still be an issue?


You place the lino mat on top of the frames in the top box of the hive. It works as a baffle to slow down the heat rising to the top and so it retains more heat throughout the hive.
I am not one to remove a QX either, I like the idea of knowing the queen is in the bottom box and laying eggs among existing brood frames…


Hi Stu, was wondering if you could suggest a bee safe product for use to seal joins?

Thanks, Macca