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Can You Put Thinset on Plywood? (Quick Answers)

When we are renovating or building a new home, tiles become a crucial part of the interior design specially when it comes to the kitchen or bathroom. However, installing tiles to walls or floors requires mortar such as thinset. 

This article explores the use of thinset with plywood tiles for flooring or walls.

Thinset on plywood

Although using Thinset is not the best choice for using with plywood because it gets affected by humidity and weather conditions – thus making it difficult to stick plywood tiles using Thinset. However, using appropriate Thinset made for plywood will get you satisfactory results.

Thinset is a type of adhesive mortar consisting of cement and sand which is used as a binding agent in flooring and walls. A thin layer of Thinset is effective at sticking tiles to surfaces in situations where the tiles cannot be directly attached to the surfaces. 

Therefore, Thinset is an effective compound of bonding tiles to floors or walls and withstand the weight of the tiles for a long period of time.

Thinset on plywood floor: 

Thinset is an effective compound for bonding surfaces to tiles whether the tiles are made of stone or ceramic – forming a strong permanent bond between each other. 

However, the surface on which the Thinset is going to be applied needs to be compatible as well – generally plywood floors don’t work well with all types of Thinset. 

Therefore, you need to make sure you are using the compatible Thinset before spreading it over the plywood flooring, otherwise it could lead to cracks and bump formation on the tile floor. 

In the case of choosing tiles, you can choose light or heavy tiles for flooring – since weight is not a crucial factor in flooring unlike walls.

Thinset on plywood wall:

As specified earlier, not all Thinset are suitable for use with plywood because of some of the properties of plywood – such as its vulnerability to humidity and weather conditions. 

This would result in the plywood swelling up and distorting its shape which would in turn affect the durability of the Thinset layer. 

In order to put thinset on plywood walls without compromising its bond strength, you need to choose a Thinset that is suitable for use on wooden surfaces. 

Another crucial matter in case of wall tiles is the weight – you need to choose lighter tiles because they would put less stress on the bond between the plywood and Thinset layer. 

Will mortar stick to plywood?

Mortar is a strong compound that is used to bond substances together specially mineral-based materials such as walls and floors as well as brick and concrete. But apart from those, different variants of mortar can also be used to stick objects to plywood. 

Since they stick well to plywood, Thinset mortar is commonly used to stick tiles to plywood floors and walls. 

Modified vs unmodified Thinset; What type of mortar to use on plywood?

There are various types of mortars available on the market but not all of them are suitable for use on plywood. Thinset mortar is used on plywood due to its high latex content that forms a bond with plywood. 

But there are two types of Thinset – Modified and Unmodified Thinset, the latter one is more suitable for use with plywood and the reasons are listed below:

Ease of preparation:

Although both types of Thinset are applied the same way by mixing in small batches and working in a number of stages, modified thinsets come in pre-mixed packages. 

Which means you don’t have to make any additional modifications to the mixture – this may seem like an advantage in most cases but for plywood, you need strong adhesive properties in the Thinset. 

In order to achieve that, you need to get an unmodified thinset and manually do the mixing to maximize its retention properties and be highly adhesive to plywood. 

Therefore, unmodified Thinset is more suitable for plywood which makes up for its difficulty in mixing.

Durability and Longevity:

Since humidity is one the key factors in determining how durable a plywood would be, it is essential that the Thinset applied is best suited to keep humidity or water out of contact with the plywood. 

In cases like these, unmodified thinset is the best choice to use due to its waterproof properties and durability in humid conditions which would protect the plywood from absorbing any moisture.

However, modified thinset is also a strong contender due to its flexibility which holds the plywood from shrinking or expanding. 

But unmodified thinset comes off as the best choice because they do not allow moisture to enter at all, thus keeping the bond durable and have great longevity.

Can you put Thinset directly on plywood?

Thinset is a compound made of cement and sand which is used as a binding agent between surfaces and tiles. It is used with a wide range of materials such as concrete, ceramic and plywood as well. 

Placing tiles directly on plywood wouldn’t be durable since the tiles would crack from the expansion and contraction of the plywood due to weather conditions. 

Therefore, you need to put Thinset directly on the plywood to form an intermediary layer between the plywood and the tile in order to create a strong bond between each other.

How do you use Thinset over plywood?

Using Thinset over plywood is no easy task given how the properties of the plywood don’t match with the best working state of thinset. Therefore, you need to be extra careful on how you use Thinset over plywood and some of those methods are listed below:

Using Inner Layers Of Plywood:

Instead of directly applying thinset over plywood, you can use intervening sheets of plywood over the plywood floor and place the tile on top of them. 

The intervening sheets should be thinner and lighter than the plywood floor itself in order to minimize the effects of expansion on the tile.

Use Exterior Grade Plywood:

Just like picking the right thinset, it is necessary to choose the right type of plywood in the first place. 

Between exterior grade and interior grade plywood, exterior grade should be used as the substrate because interior grade plywood such as Veneer forms an unstable base for the tile due to its hardwood top and bottom layer. 

Exterior grade on the other hand does not give rise to such instability and thus is appropriate for use with thinset.

Use Thinset with High Latex Composition:

Latex is one of those components of thinset that determines how strongly the mortar would adhere to the surface and that is more important in case of plywood since it is subject to deformation depending on the weather condition. 

Therefore, you need to choose a thinset that has a higher latex composition in order to have a stronger bond between the tile and the plywood. 

Unmodified thinset is the best fit for such cases since you can mix additional latex additives to it to increase the latex composition.

Allow Gaps For Expansion

While placing the plywood, make sure to keep in mind to keep enough space for the expansion and contraction of the plywood. 

Keep at least a 1/16 inch gap between adjacent sheets of plywood so that they don’t end up pressing each other and forming a crack when they expand. 

Can you use Thinset to level a plywood floor?

Thinset is an adhesive mortar used to bond tiles to different surfaces such as floors and walls. The layer of thinset is effective at sticking tiles to surfaces such as plywood floors where tiles cannot be attached directly. 

However, this does not imply that thinset can be used to level a plywood floor because as the name suggests, thinset is to be applied in thin layers. Once its thickness exceeds the maximum thickness specified by the manufacturers, the thinset begins to lose stability. 

If a layer exceeds ¼ inches in thickness, it would stop adhering to both surfaces as effectively as before. Even if the thinset is layered after the previous layer has been cured, the new layer would bond with the old layer and make the entire structure unstable.

Final thoughts

Thinset is not the ideal material to use with plywood since it is susceptible to changes in humidity and weather, which makes it challenging to attach plywood tiles to Thinset. However, using the proper Thinset designed for plywood will produce results that are satisfactory.