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Algae and Moss on Greenhouse floor

I had a 6x8 aluminium greenhouse erected 18 months ago. It's on a new concrete base specifically made for it. The base is level and smooth.

I employed a professional greenhouse engineer to put it up.

Since then the floor floods whenever it rains hard and the wet floor is covered in soggy algae . I Have 3 automatic vents so it's not coming in through the roof [I've watched it!] The water seems to seep under the base and sit on the floor - when it gets warm again then the film of stagnant water grows moss and algae and I have to keep scraping it off.

Should I somehow seal the tiny gap between the base and frame to stop the water creeping in? Should this have been done when the structure was put up? 

Thanks for any information!


  • Singing GardenerSinging Gardener EssexPosts: 1,214

    My greenhouse is sealed around the edge with a tube of waterproof outdoor sealant/adhesive from the local DIY shop which was applied after the greenhouse was installed - and can be reapplied as necessary.Think about leaving holes for water to drain out if necessary though - we initially forgot to do this and ended up with a flooded greenhouse because of the automatic watering setup!

  • Allotment BoyAllotment Boy North London Posts: 5,829

    If you do as above & you still have a problem you may need to use an angle grinder & cut one  two small drainage channels in the concrete. You would have to use a masonry drill to cut under the frame. It won't be easy. Ironically though the standard advice is for a level base you really need a very slight fall to one direction, but as you can't really do this retrospectively you are stuck with the above suggestions.

    AB Still learning

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