How To Replace or Repair Rot Damaged Wood Siding

You have a well landscaped yard with beautiful flower arrangements placed carefully along your property, your window trim, porch and fence all look great! But there’s one problem, your wood siding on the exterior of your house is falling apart and rotting! Well, don’t worry because when you read on you’ll figure out how to fix rotted wood that has decayed and how to replace rotted exterior wood siding or repair it with epoxy.

How To Replace or Repair Rot Damaged Wood Siding

Materials That You Will Need to Repair Rot-Damaged Wood Siding


• Safety Glasses
• Chisel
• Paint
• Paintbrush
• Measuring Tape
• Replacement wood siding
• Nails
• Hammer
• Circular Saw
• Epoxy
• Epoxy Primer
• Utility Knife
• Acrylic Caulking
• Rag
• Pencil
• Putty Knife
• Pry Bar
• Borate
• Sand Paper


1. Patch Wood Siding


  • You may think that your wood
    siding should be able to withstand any kind of moisture and damage right? Just like any type of wood – there is a chance it can rot. If you have wood siding that has started to rot – you may be able to patch it – depending on how severe it has rotted.
  • Find a small part of the wood siding and remove the damaged section if it is visible enough to know the rot is in a specific place and not throughout. It is important to patch the wood siding as soon as there is evidence of rot so you can prevent the rest of your wood siding from being completely rotted through.
  • After you have removed the part of the wood siding, make sure you have clapboard that will fit in flawlessly with your existing wood siding so it won’t look out of place. *Use the removed rotted piece of wood siding as a template for the exact measurements for the replacement siding.
  • Use a paintable acrylic caulking around the opening on the side of the house and try to slide the thinner side of the clapboard underneath the board above the opening of where you cut from. Then carefully push the board in tightly. Use 8d nails into the wall studs ¾ inch up from the bottom edge of the replacement board and also the bottom edge of the piece above it. Do this carefully; you don’t want to split the wood.
  • You can then cover up the nails with the acrylic caulking and wipe away any excess with a rag. Then you’ll want to prime this patch and let it dry. Once dry,  paint it the same colour as your existing wood siding with two coats – dry overnight and apply a second coat.

2. Replace Severely Decayed/Rotted Wood


  • If you have found that your wood
    siding has rotted or decayed pretty severely, mark the start and end of the rot off with a pencil, put on your safety goggles and cut out the rotted wood siding piece using a circular saw. Use a hammer to get rid of any nails that hold the wood to the structure and, using a chisel, finish cutting the wood and detach it.
  • Now you’ll need your replacement piece that you have measured to fit in perfectly, and just like you would patch like the steps above, you will do the same thing. Slide in the replacement carefully and nail it together with 8d nails. Prime regularly, let dry and paint the replacement piece with the same colour as your existing wood siding with two coats – dry overnight.

3. Repair Rotted Wood Siding with Epoxy

  • Like the other two steps, get
    rid of any rotted siding either with a chisel, saw or hammer/pry bar and inject borate into the hole. Borate is a wood preservative and it can be drilled halfway into the wood to be sealed over with epoxy. Borate basically seeps into the wood and will minimize rot/decay in the future.
  • Using an epoxy primer – brush it on the wood that has been exposed. Allow a 10-20 minute dry time and then wipe away any excess with a rag.
  • Apply the epoxy with a putty knife and sculpt carefully overtop the primed area and allow to dry.
  • Prime with an acrylic primer, and paint over the epoxy with two coats of paint.



  • Smaller cracks or holes in your wood siding should be sanded and then filled with wood putty, sanded smooth again and primed and painted as well.
  • Sunlight will break down Epoxy, so be sure to paint it as soon as it has dried – if you are completing this project in high sunlight.
  • Use a two-part epoxy primer and paint for optimal results

Wow that was a lot of steps! If you’re a regular reader, you have become a pro D.I.Y repair man (or lady)! Replacing or repairing rot damaged wood siding may seem like lots of steps but you won’t be doing all of these, just the ones that apply to you. In most cases, wood siding does last awhile and you probably have started to see evidence of rot before the decaying got to be a horrible situation – and just a quick patch is all you need to do. But, if you have found your wood siding is rotted or decayed at a level you just don’t think your patience will tolerate – then give Home Painters Toronto a call and we’ll happily do it for you! Call us NOW at 416-494-9095 or sned us an email at