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Rotten Plywood Under Siding: Everything You Should Know

Did you just find out that the plywood under your siding is rotten? We can understand your worries as a homeowner. But you can try to solve this issue by yourself.

Probably, you’re confused about how to remove the rotten plywood under siding

Firstly, you must detect the problem, by applying the screwdriver method. Check if the screwdriver can make a hole through the plywood. If yes, then you’ve to replace the rotten section. This includes removing, finding studs for nailing, and replacing the new layer.

This is just the tip of the iceberg. Now we will dive deep into this. Spare us some time. You’ll get a complete idea about this by the end of this read.

Reasons And Effects of Rotten Plywood 

Rotten Plywood Under Siding: Everything You Should Know 1

Builders use a plywood layer before installing siding to strengthen the structure. The plywood is also laminated with waterproof material. So it can work like sheathing too. 

Even if your wall has a flashing inside the siding, plywood is suggested. As it can provide better resistance against water damage. 

Rotten plywood can happen for several reasons. Firstly, continuous contact with water and moisture can cause damage. Another reason could be a moth or pest attack. This is the indirect result of liquid contact.

The rotten layers aren’t exposed to the outer world. Unfortunately, it takes a while for the owner to understand that the layer has been rotten. In most cases, it comes to their concern during remodeling. By then, huge damage has already been done to the house.

The effect of rotten plywood is unimaginable. It can cause structural damage. It can even make your house very prone to disasters. As a consequence, it can lead to serious mishaps. Which can end up costing you a hefty amount of money.

You can additionally look into Dutch lap other than vinyl siding. If you are interested in changing your preference.

How To Detect Rotten Plywood

As we already know, plywood rotting is an extremely serious issue. It needs to be addressed as soon as possible. 

This problem however isn’t an easy one to detect. Luckily we know of some locations in your house more prone to this. 

Places that have sidings without sheathing or flashing between pavers are riskier than others. Also, locations that are more exposed to outer surroundings can get affected easily.

Check the following locations to make sure your house is in the right condition:

  • Damaged Roof
  • Windows
  • Basement
  • Wetrooms
  • Exterior Deck
  • Doors 

These places have a higher chance of rotting than usual. So, you better be concerned about them. 

Now, let’s move onto detecting the problem. Firstly, try to notice the color-changing or paint peeling near the siding area. It indicates water damage and the presence of moths, fungi, and pests. 

Look for noticeable water spots on the siding area or behind it. Put your finger in between,  to feel the moisture or swollen wood. If you can, the rotting has already started. 

You can try inserting a screwdriver into the wood as well. If it can make a hole, your plywood is problematic. As it’s not supposed to be this soft. 

Now you can start replacing the rotten plywood!

Safety Measures Before Installing Plywood

Before replacing the rotten part, take some safety measures beforehand. 

Here are some important precautions that you must follow:

  • Try using gloves and goggles. Rotten plywood has moths and pests growing on it. Thus, try to keep your eyes and skin away from them. 
  • Using a safety mask will be a good decision. Crumbling wood will create a lot of dust and shattered wood pieces. This dust can be harmful to your respiratory system. 
  • If your plywood layer is largely affected by pests, contact a professional pest controller before. You shouldn’t start your replacing project before getting rid of them properly.

Step-By-Step Guide to Replacing Plywood

We have already discussed the problem and its adverse effects. We’ve also got prepared to start the problem-solving part. 

Let’s start the step-by-step solution process:

Preparing The Toolbox 

Before going straight to work, let’s go over what you’ll need. So that you can concentrate on your work properly. We’ve made a list of the must-needed things:

  • Small Pry Bar 
  • Drill machine
  • Jigsaw
  • Nails and nailer
  • Plywood
  • Hammer

Get your tools in your toolbox so we can start. Let’s not waste time and jump to the next part.

Removing The Siding 

Firstly, you need to take off the existing siding. Use a small pry bar to take off the nails. Then you can easily remove it.

It’s better if you have a helping hand with you. In some cases, the siding tiles are too heavy. Sometimes, you even need to remove the whole plywood layer. So, it’s better to have someone around to assist. 

Finding The Stud Edge and Removing The Damaged Part

You need to cut the sheathing plywood from stud to stud. Then drill a couple of holes to find the stud edge. There is no certain amount of holes. Keep drilling holes until you find the stud edges. 

After finding the edge, cut out the damaged section. You can use a jigsaw for this. Jigsaws can cut anything from metal ductwork to various kinds of siding. 

We can understand your concern about finding a suitable jigsaw. Therefore, we listed our best picks for you here:

Product 1
Product 2

Hopefully, you can easily select your tool now. It’s time to cut the rotten part out. Then take it off. 

Attaching The New Plywood

Now you’ll cut the new plywood to replace the cutout portion. Create holes for nails with a nailer beforehand to drive the new portion. The nails will get inserted through those holes. 

Nail this part carefully. Otherwise, they might fall off the stud. As a matter of fact, wood and plywood are different in many ways. Thus, plywood needs more nailing than other wood. 

You’ve successfully installed your new plywood layer. Now just reinstall the siding layer. Hurray, we’re now done with our tiny renovation project. 

In case you are interested in a new type of siding. You can look into Dutch lap and Clapboard siding for further revamp.


Question: Do you put plywood under siding?

Answer: Putting plywood under the siding is always a good idea. You use other types of water protection under your siding. But we would still suggest a layer of plywood in between. It’s even better if you use exterior grade plywood for this purpose. 

Question: Can Plywood be waterproofed?

Answer: Plywood are layers of wood put together, and laminated with waterproof material. So, theoretically, it’s supposed to be waterproofed. But in reality, they are vulnerable to water damage. Especially if it’s exposed to moisture for a long time. 

Question: How long does it take for plywood to rot?

Answer: Plywood are supposed to last forever. But the prerequisite is keeping it dry. If it comes in contact with moisture, damp or water, it will get rot. The more it’ll be exposed to liquid, the chances of rotting earlier will increase.

Take Away

That’s all you need to know before replacing rotten plywood under siding. Now you can easily proceed to your mission. 

Don’t waste more time and put on your handyman cap.

Our best wishes are with you!