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How To Install Hardwood Floors Directly Over Joists

Hardwood floor joists

What Are Floors Made Of?

Let’s take a quick look at the structure of the floors in general:

  • First, we have the joists. They are an essential structural element forming the base upon which rest all the other flooring components. All houses have joists, except those with a concrete slab subflooring.
  • Next is the subfloor. It is installed directly on top of the joists and provides more overall stability as well as a certain amount of moisture protection. The subfloor is typically made from plywood or oriented strand board (OSB).
  • The underlay is the third element and is only a necessity when you are having a floating installation. (A method of fitting where the planks or boards are attached by snapping, glueing or nailing them together without securing them to the subfloor.) However, such an underlay can work on all types of wooden floor and provide additional benefits like cushioning, sound or heat insulation and an additional level of moisture protection.
  • Finally, we have the finish or top floor. This is the visible surface upon which we do our everyday activities. It can be solid hardwood, engineered, parquet, laminate, vinyl, etc.
    This is the typical structure of a floor. However, is it possible to install our finish floor directly over the joists without a subfloor in between?

Wood Floor Fitting Over Joists

Wood flooring nailed down over joists

To answer directly the question – Yes, it is entirely possible to install hardwood flooring directly on top of the joists. Both solid wood and engineered can be fitted this way. The main concern you should have with this method is just how large is the space between your joists? In general, they shouldn’t be more than 45cm apart. If the gap is bigger than this, it’s possible to use noggins and braces for support or simply install a plywood or oriented strand board subfloor first before laying the top floor.

Truth be told, having a subfloor is just better overall. A subfloor helps limit the effect of draughts and moisture, ensures better insulation, provides a more stable base for your finish floor and any installation or additional fixing will be much easier to perform on top of it. Also with this, you don’t have to worry about the maximum space between joists. It won’t matter anymore.

Few Tips on What You Should Consider

Underfloor insulation

The Joists

The most important factor if you consider the direct installation is the condition of your joists. You must make sure that they are stable, relatively dry and properly levelled. If you find that your joists are not dry, you should find out what could be the cause of this. If you suspect that moisture problems can appear in the future, we suggest that you avoid fitting right over the joists. Consider a proper subfloor instead since it absorbs some of the excessive moisture that could otherwise be transferred directly to your finish floor. This, combined with a good underlayment can ensure that the top flooring layer lasts longer and looks better!

The Boards

Wood floor over plywood

Keep in mind the subfloor also helps spread the weight of everything on top of it more evenly. This means that without it, you can expect more pressure to be put on the planks or boards and you need to make sure that they are thick enough to take it. We recommend a width of no less than 20mm and a length of around 6ft for a hardwood floor.


A small detail people can easily forget about. Imagine having installation over the joists on the second floor of your home. No cushioning, no insulation of any kind. Every sound, every footstep will be heard. If privacy is a concern, you may want to stay away from this method of installation for certain parts of your house, especially bedrooms.

Underfloor heating

The fact that you lack a proper subfloor doesn’t mean you cannot use underfloor heating as long as you have engineered hardwood. The heating system can be installed between the joists with little trouble.

FlooringFirst! Services
158 Coles Green Road
London, NW2 7HW
T: 020 88309782