How To Kill Moss On Your Garage or Carport Roof

A problem often faced by homeowners is the growth of moss on garage or shed roofs.  Moss is not only unsightly; it also harbours damp, which could cause long-term damage to the building's roof.  You can remove moss and prevent it from growing back by following these guidelines.

How to get rid of moss

Although you can buy moss-killing products from DIY and garden centres, it's actually cheaper and more effective to use the following tactics.

Plan 'A'

Mosses like conditions that are shady and damp.  If your garage or carport has trees or bushes overhanging it, they could be creating the perfect environment for moss to grow in.  Wherever practical, remove these shade providers and expose the moss to bright sunlight.  This will help to kill off the moss as well as preventing it from growing back.

Plan 'B'

What you'll need

  • stiff yard brush
  • hose pipe and running water supply
  • baking soda
  • warm water
  • large garden sprayer (available from garden centres)
  • ladder

How to do it

  1. Begin by using a stiff brush to knock any existing moss off your carport or garage roof.   
  2. Now hose the roof down with cold water to get rid of any remaining debris and moss spores.  If possible, hose the roof from the apex down so that you don't accidentally spray water underneath the eaves.  If you're using a ladder for this job, always ask someone to 'foot' it for you, in case it slips.  
  3. Make up a strong solution of baking soda and warm water, and fill up the sprayer reservoir with it.  Liberally spray the solution over all areas of the roof where moss has been growing.  
  4. Repeat this moss dressing process in the spring to prevent wind-blown moss spores from germinating on your roof, and again at the end of the summer to kill any that might overwinter there.

How NOT get rid of moss on roofs

Although it may be tempting, never use a pressure washer to blast moss off your roof.  High pressure water jets could cause damage to roofing materials, especially shingles.  

Also, don't try to scrape moss off the roof using a sharp-bladed instrument or shovel.  This is highly likely to cause cracking or other damage to the roofing materials and won't get rid of the moss permanently anyway.

In conclusion

You can remove moss from your garage or carport roof by following the guidelines above.  Dress your roof twice annually to prevent moss from returning.