I live at the top of a mid-rise block of flats and the top flats are inset slightly such that each has a balcony/terrace area. I'd like to put some sizeable planters in this space (175 litres). However, I don't know if this would be too heavy for the terrace.

How could I find the maximum pressure / load I can put on the balcony? Do you this could cause damage to the property?

Some extra info:

  • The flat is in london and construction finished last year.
  • We have had parties were we've had 10+ people in this space. However, the load there was obviously temporary.
  • I think each planter should weigh ~100kg.

2 Answers 2


As I see it, you've got two choices: hire a structural engineer to calculate it or get with the builders and check the plans. If the building is only a year old, plans should be available. You could also try to track down the architect if it was done locally. They would have the plans. Building and zoning departments would have plans and the weight limits might be on them.


In the U.S. we have a Building Code that stipulates the minimum load allowed that decks and balconies must support. Not all jurisdictions (cities, counties, etc.) adopt this Code or they adopt it but modify it by increasing or decreasing certain issues. So, it’s important that you go to your local jurisdiction and ask what they require. (Seldom do builders increase required minimums, so you’ll be able to determine what they used.)

Here is what our Code requires and it will give you an idea of what is allowed. 1) Live Loads (the greater of people loads which is 60 lbs. per square foot (psf) for balconies and 40 psf for decks or snow loads which is usually around 20-25 psf.) People loads are often considered impact loads, because they don’t stay on the balcony very long… like furniture, planters, etc. I’d use 60 psf. 2) Dead Loads: include all the material used to support the deck or balcony. Usually that’s about 10-15 psf.

You can calculate what your balcony can support. If your balcony is 6’ wide and 20’ long (sorry you’ll have to convert to metric) then the maximum allowable weight is:

6’ x 20’ x (60 psf + 25 psf) = 10, 200 lbs.

Now, that number needs to be adjusted down if they used preservative treated lumber , if it’s a deck instead of a balcony, etc.

In recent years there has been a problem with balconies falling off walls because of improper connections. If you add a planter it’s considered a “point load” and may need extra support where it sits and may need extra connections. I’d definitely have an architect or structural engineer (not a civil engineer) review your situation. (When you load that planter with water it will weigh a ton. Sorry, that’s an American expression that means it weighs a lot.) I’d think about wher all that water will drain. Neighbors don’t like that dripping on their balcony.

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