# What is optimal bottom for top bar hive?



## blist (Jun 15, 2010)

I am in south Texas and I build my hives with a solid floor...it seems a lot of people build screened bottoms thinking about ventilation, however, that my actually be counter productive (in regards to ventilation)...with a solid floor, the bees can regulate the temp. to their liking, with a screen floor, they can't do that...however, I have top bar hives with end entrances, so using a barrel hive may be a bit different


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## PatBeek (Jan 13, 2012)

blist said:


> I am in south Texas and I build my hives with a solid floor...it seems a lot of people build screened bottoms thinking about ventilation, however, that my actually be counter productive (in regards to ventilation)...with a solid floor, the bees can regulate the temp. to their liking, with a screen floor, they can't do that...however, I have top bar hives with end entrances, so using a barrel hive may be a bit different



Very interesting.

The entrance on mine will be on the end also, through the barrel cap. Just curious, why would the entrance point be a factor?


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## blist (Jun 15, 2010)

well, I'm thinking in terms of bees moving air...I will see my bees line up across the bottom entrance on the end and cool the hive all the time, they line the whole width...if it was a side entrance, not sure how effective the air circulation would be


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## PatBeek (Jan 13, 2012)

Yeah, and I wonder if a raccoon or possum could swipe their little paw up into the hive through the screen and try to help themselves.


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## Michael Bush (Aug 2, 2002)

When Huber did his experiments on hive ventilation he concluded that the maximum ventilation was with one opening and more openings made LESS ventilation. I think the point is the bees can manage a limited opening. Too many and they can't manage it and it can get away from them. They have to COOL the hive on a hot day and you making a lot of ventilation is like running the air conditioner with the doors and windows open... they need to control it. I do think some on the bottom and some on the top in a vertical hive can be helpful in the midst of a flow as SOME of the ventilation will happen by simple convection or chimney effect relieving some of the work. But if there is too much they the bees are fighting to control some of what is naturally happening in order to maintain the cooler temps inside than outside.

In a horizontal hive I find the bees are in less of a battle with gravity as all the air flow is more horizontal so heat and humidity are not driving the air up and the bees trying to force it back down. I like a solid bottom in a Top Bar Hive.

http://www.bushfarms.com/beestopbarhives.htm#ventilation


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## PatBeek (Jan 13, 2012)

Michael Bush said:


> I like a solid bottom in a Top Bar Hive.
> 
> http://www.bushfarms.com/beestopbarhives.htm#ventilation


Hmmmm.....Well maybe I should then turn that into some sort of bottom observation window by placing a strip of plexi-glass on the outside and then some sort of unlatching cover for it. But I'm sure there'd be too much debris covering it anyhow after awhile.

Thanks, Mr. Bush. I'm not really sure how I should proceed at this point. I suppose I may consider just sealing it back up completely.

.


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## Michael Bush (Aug 2, 2002)

You could rig some way to put a tray under it and then adjust it and see how they respond. There are a couple of tipping points though. A big one is when the outside temps exceed 93F.


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## blist (Jun 15, 2010)

what is interesting is I didn't have a single comb collapse last year and I'm in south Texas...most days were over 100 and we had an extreme drought last year

however, I'm thinking some of it has to do with heat transfer on the roof of the hive as well...the cover on that hive only made contacts on the ends, then it had an attic (air space) and a "roof"

I just put a new hive in and the cover directly contacts all the bars...I'm actually thinking I want to build some air gap on top of the cover so it doesn't get as much heat transfer to the bars


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## mrobinson (Jan 20, 2012)

All that I know is what I _did:_ I put in a solid bottom.

My rationale (if there was one) is simply that a bee-tree doesn't have a screen floor. If the bees drop something (like pollen, for instance...) they ought to be able to just go right down there and pick it up, whatever it is, without having a well-intentioned screen barrier in the way. Since it didn't make sense to me to put such a thing in, I didn't. 

Ask me in six months or a year if my bees decided that I was right. I've no way to know until then.


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## blist (Jun 15, 2010)

I highly doubt your bees are going to tell you it was a wrong decision. Your rationale is good IMO, there aren't too many trees out there with screened bottoms. 

I would think a screen would actually create more work...i.e. the bees will fill it in with propolis (if you are trying to harvest propolis, perhaps you want that). Michael already pointed out the logical and more scientific data about it.

I don't think you will get a definitive answer in regards to an absolute good or bad because there are people doing it successfully both ways. I have noticed that nearly all the designs I've seen with screened bottoms do have a cover that actually slides under the screen (or something similar) so that it isn't always completely open without any way to close it up.


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## PatBeek (Jan 13, 2012)

Someone today told me I should place 8-gauge hardware cloth there. Isn't that the size where it's 8 squares per inch? And isn't that what is in the bottom of Langs?


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## Michael Bush (Aug 2, 2002)

>Someone today told me I should place 8-gauge hardware cloth there. Isn't that the size where it's 8 squares per inch?

Yes.

> And isn't that what is in the bottom of Langs? 

When they have SBB usually. Betterbee uses #6.


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## itscbiz (Mar 5, 2012)

I am not so sure a ventilation slit in the bottom would do anything for ventilation. For air to move on it's own you need ventilation holes/slit on the bottom AND on the top. This way hot air can escape through the upper hole and cooler air will be drawn in through the lower hole. I have not yet tried screened bottoms, but I do have ventilation holes just below the lid on the opposite side of the entrance. I use holes so I can close them with a cork in winter.We get very hot days in Arkansas and some beekeepers had their combs melting or getting soft enough to drop off. Climate and even just the location of your hive needs to be considered. I would suggest you just build another hive (one with and one without screen) and do a comparison. And share more of your pictures.


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## Keefis (May 4, 2012)

Your best option is just that, options... I mean, I have a screened bottom board for summer use as well as pest control.(small mites etc fall through the screen rather than attaching to another bee. Then I slide the solid board in there when winter comes. Then you can truly see the differing effects on YOUR hive. 
So make it removable and your set no matter what.


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## tomohern (May 7, 2012)

So I built my TBH with solid bottoms based on Michael Bush's plans. The bees seem fine so far but now I am wondering about mites. 

How do you monitor for mite levels without a screen and a removable bottom? Are the mites that get groomed off able to just climb back up and reattach to new bees?


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## Keefis (May 4, 2012)

mites can and will climb back up and attack again, if they don't fall out the screen bottom.
I say make two interchangeable bottoms one closed and one screen,to better suit whichever situation you have.


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## tomohern (May 7, 2012)

Well, my bees are already in the hives, so I think it is too late to make design changes.


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## Michael Bush (Aug 2, 2002)

Screened bottoms are nice for monitoring mites. I don't see that they make any difference in the numbers.


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## tomohern (May 7, 2012)

And that was my question: How do you monitor for mite levels without a screen?


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## conifer (May 5, 2011)

tomohern said:


> How do you monitor for mite levels without a screen?


You can do an icing sugar shake if you don't want to kill bees, or an alcohol wash if you do.

Do a google search for the details, I am not sure what the thresholds for treatment (ratio of mites per # of bees) are offhand.

*Edit: Here is a link with info on various detection methods and info on thresholds for treatment http://www.agf.gov.bc.ca/apiculture/factsheets/222_vardetect.htm


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## conifer (May 5, 2011)

We use a screened bottom, along with a solid wood bottom board which we can open, close and remove as needed: 

http://thehoneybeat.com/2011/07/our-top-bar-hive-bottom-board/

I can't say that the screened bottom is the main reason, but we haven't needed to treat for mites in the 3 years we've been using KTBHs. We have done the occasional icing sugar dusting as a precaution, and we do drone trapping when we find full bars of capped drone brood.


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