Caring for A Polystyrene Hive or Nucleus

Polystyrene Nucleus Hives – Cleaning and maintenance.

I was preparing to clean 3 association poly nucs and thought it may be worth sharing how I go about cleaning and caring for them.

Firstly a bit about poly nucs.  Anyone beginning beekeeping in 2020 would be forgiven for thinking that poly nucs were the only game in town, most suppliers now have either their own brand or sell one of the other makers. This was not the case 10 years or so ago when I started, then the arrival of Paynes poly nucs and their rapid approval and adoption was big news.  I now have 4 types of poly nuc from 3 suppliers, they are not all equally useable.  However the main issues of maintenance and care are the same.

What is a Nuc or Nucleus Hive?

Most hives designed to take frames can manage 10,11 or 12 frames in each box depending on:

  • Hive type,
  • Who built it
  • Beekeeper preference for spacing!

A British National hive ought to take 12 Hoffman frames at about 32mm spacing, but 11 is more usual, with the gap being filled by a Dummy Board.

A Nucleus Hive is simply a cut down hive with boxes taking 3, 4 or 6 frames. They are usually used for queen rearing, but are also useful for:

  • swarm collection,
  • isolating queens during inspections,
  • bait hives
  • over wintering small colonies
Thornes poly Nuc

To name but a few.  Traditionally these were made of various timber products, Cedar being the Rolls Royce, but plywood being a close second.

They advent of Polystyrene as a material for hives and nucs improved the improved lightness and thermal properties meant that the functionality also nucs improved dramatically.  The range of additional boxes, brood, supers, ekes, and feeders has increased over the years and they are have become indispensable as part of the beekeepers standard kit.  In fact if asked about beginners kit a nuc would be high on my list.

To Paint or not to Paint?

The first and continuing debate is whether to paint or not to paint, and if so with what!.  Polystyrene is a thermo plastic and is resistant to water absorption, however when it is foamed there are of course bubbles of gas which create the insulation effect, they also increase the possibility of some liquids getting inro the surface.  The other issue is dirt and mould, which also impact on woodedn boxes of course, but on unpainted polystyrene mould appears to get into the top surface and can be difficult to remove.  Probably this is of little consequence to the bees and if chemical sterilised will not increase future mould growth in future.  However it looks unsightly, is difficult to clean, and may increase permeability and mould growth if unpainted.

Painting is designed to improve all of these:

  • Improves the aesthetics of the hive, choosing different colours is supposed to help bees recognise home!
  • Seals the surface of the polystyrene, maybe improves water resistance, especially useful on the inside surface of feeders.
  • Makes the box easier to clean dirt, propilis and mould do not stick quite as much.

I have settled on Dulux Weathershield masonry paint.  Good range of colours, (if that’s of interest) covers well and wears reasonably well.  More importantly it dries well and does not weld parts together unlike Garden Shades.  It should be said that like paint on any material bees seem to like chomping it off, so it will need touching up, also paint wears off especially near entrances remember each bee should have six feet and there are thousands of bee journeys per day!  Don’t be surprised to find wax with a hint of colour!.

Others use water based gloss paints especially on the inside of feeders. 

Below is an unpainted nuc, near the entrance the staining remains from black mould after soaking in bleach and scrubbing.  The shape of the removed entrance disc can be seen indicating the bleaching effects of the sun.  Paint will seal the surface, give some protection against the sun and give a smoother surface for cleaning, in theory at least!  It also looks better and gives the opportunity for the artistic beekeeper to express themselves, which is recommended by some on the entrance surface to help bees find home!  I would recommend painting the inner surface of feeders at least as this can be prone to black mould, and anecdotally some feeders have been suspected of leaching food.  Any split food will attract bees, wasps and other critters with a sweet tooth and they will munch the polystyrene whilst trying to get the sugar.  More of repairing that damage later.

After a while you will notice many edges and any painted surfaces the bees are exposed to become worn and chewed, no matter what the material the hive is made from maybe with the exception perhaps, of hard plastic.  Not sure if paint attracts or offends bees, but either way they like to remove it and on occasions artistically incorporate into wax,  I have wood entrance blocks with all the edges nicely rounded and paint removed.  You may also notice on some nucs the entrance being opened up, this maybe down to mice on some occasions but I suspect bees and perhaps wasps are also involved.  My first Paynes poly hive was probably 6 years old before it became chewed once they had decided it was worth chewing, they seemed to attack all surfaces including the inner edge of the roof.  I cannot imagine what they find of interest.

Mouse damage?
More damage, Mouse, Bees or Wasps who knows!
Entrance damage

The Kit

Here is my collection of cleaning kit.

  • Tray big enough for nuc and able to hold sterilizing liquid
  • Bleach
  • Commercial Hive clean
  • Pressure sprayer, makes life easier
  • Paint scrapers for removing wax.
  • Screwdriver to remove entrance disc and mesh
  • Scrubbing brush and old manual toothbrush (I’m sure an electric one would work just aswell!)

The process.

  • Strip down the nuc as far as possible, the latest Maisemore design has a mesh held by screws, lots of screws! Still best to remove this as it overlaps the floor and the hive detritus collects here.  Bees don’t seem inclined to clean this up and wax moth love it, should be said polystyrene is not wax moth proof.
Maesmore Nuc: Ne floor. Rubbish trapped under mesh
Wax moth heavean!!!
Mesh removed
Underside view. Unpainted nuc
Plastic entrance disc removed: Note staining and sun bleaching of plastic
  • Scrape off any wax and propolis and any squished bees using the scarpers, remember to keep the angle as low as possible to avoid digging in.
  • I wash the nuc just with water if it looks very grubby and have a bit of a scrub to assess the depth of dirt.
  • Next I either spray with Hive Cleanse and leave for at least 20 minutes, perhaps scrubbing very dirty parts, or I place the nuc in a tray of diluted bleach.  Ideally the container would be deep enough to immerse the whole nuc, but I haven’t found a suitable container, so I keep turning the items and weighing them down if they float off!
  • Drain and leave to dry

NOTE: although Hive Cleanse clearly states not to be in contact with bees! and I assume the same is probably true of bleach I do not think it necessary to rinse down after use.  You can be your own judge.


Since creating this article I have tried out using a steam cleaner on poly hives. Success…..which I had done this earlier. So process is as outlined above but now I use a steam cleaner to sterilise and melt off any wax and propolis. Works really well and so far not melted the poly. I suspect any hard plastic parts might be subject to warping if the steam claening is over done. As with flaming a wooden box keep the flame/steam moving is the best advice!

Next I assess the nuc and its parts and decided if the paint needs touching up or holes and dings need filling.

Warped plastic disc
Maesmore Nuc with Replacement metal disc

Damage Repairs.

Inevitably any hive can become damaged.  Boxes are dropped, hive tools are sharp and many animals will attempt to gain entry into a hive, Green woodpeckers can be a particular problem.  These will destroy wooden hives including plywood when determined, but polystyrene puts up less resistance.

Small dents and nicks can be filled with a good exterior grade filler and then sanded back.  If the hole goes all the way through then it maybe necessary to place something such as a block of wood covered in cling film or sheet of plastic, to prevent the filler falling through.  If the hole is particularly big then adding a piece of mesh will reinforce the fix.  Make sure the filler is proud of the surface as most tend to shrink.  I have tried using spray foam on large woodpecker holes, whilst this filled the hole the one I chose was a favourite with the bees and the chopped it all the way through!

I have also used Duct and Gorrilla tape to strengthen or protect vulnerable edges and seal off the feeders on Paynes nucs. 

Finally reassemble.  We recently tried to move a nuc of bees and were horrified to find the entrance disc had warped to the extent bees were able to get out with it fully closed.  Duct tape to the rescue!  I have since found stainless steel discs available from Simon the Beekeeper for £2 so giving them ago.

Now would be a good time to repair any damaged paint.

One of the joys of polystyrene hives and nucs is that they keep on developing and changing and sometimes improving!  Unlike commercially made wooden designs which have been largely unchanged for years though some of the peripheral parts have developed.  For instance Maisemore which is my preferred nuc at the moment, has a new mesh floor and roof.  The mesh floor now screws in and can be removed, the previous design could not.  Though as pointed out above this now traps muck which need attention.  The roof is now much deeper and thicker, so it has storage space or will cover a pack of fondant, and is more thermally efficient.#

Maesmore roof: Old style on the left, new style onthe right.