Laying Oak Flooring Onto Joists

14th Apr 2016

Nowadays oak flooring is laid in a number of situations and environments. Probably the most traditional method of fitting is to lay oak flooring onto joists.

Whether you intent to lay solid or engineered oak flooring, when laying onto joists we recommend our 20mm oak flooring. Our 14mm solid oak flooring has been specifically designed for laying over either an existing wooden subfloor or a plywood subfloor, and so is therefore not recommended for fitting onto joists.

Choosing whether solid oak flooring or engineered oak flooring is most suitable for your area depends on a number of different factors. For example; if you intend to install an underfloor heating system or lay the floor in an area with changeable humanity - engineered oak flooring would be the recommendation. Due to its construction, engineered oak flooring is much more stable in changeable areas (compared to solid oak flooring). In more stable areas over joists, solid oak flooring is more often than not used.

Floor Joists

When fixing to joists, the secret screwing or secret screwing method is the preferred method of fitting. This involves driving a nail or screw 45 degrees into the tongue of the oak flooring board. For the secret nailing method a porter nailer is required. Whereas when using the Spax Screws only a cordless hand drill is required.

The great advantage of using Spax Screws is that no pre-drilling is required - meaning it will take half the time to lay each board. The CUT narrow head of the screws means the wood won’t split as the screw goes in. Once the screws are in, they wont rot the oak - they’re galvanised and yellow passivated. Regardless of whether you secret nail or secret screw, these fixings should be fitted at every joist.

When fitting wide solid oak flooring onto joists (boards wider than 160mm), our recommendation would be to combine the secret fixing method with the surface fixing method. Surface fixing involves driving a nail or screw through the surface of the board. When nailing, a traditional floor brad is used and the fixing is left exposed - creating a more "traditional" looking oak floor.

Surface Fixing Oak Flooring

For those who don’t like the look of exposed nails, the screwing and plugging method is available. This method involves screwing into the surface of the board using a suitable screw. The head of the screw is then concealed using an oak plug. Again, these fixings should be fitted at every joist.

If you would like to discuss fitting oak flooring onto joists with us further, please give us a call on 01538 304584.


Please can you advise whether the tongues should be glued?

Also I want to put solid oak over underfloor heating - how can we mitigate the risk of gaps.

Mike September 27, 2018 at 10:37am

Hi Mike,

When laying Solid Oak Flooring we would not recommend laying the floor as a floating floor. Solid oak flooring should typically be screwed or nailed down. When laying over underfloor heating we would recommend using Engineered Oak Flooring - which would be more suited and stable in this environment.

Peak Oak September 28, 2018 at 9:52am

Hi there Peak Oak
I'd like to use your engineered flooring to replace (not go over) old floorboards in an upstairs bedroom. This would therefore be going directly onto existing joists. There is no underfloor heating. Can you advise:-
Will it be OK to fix (secret screwing or nailing) your engineered flooring direct to each joist?
Sincere thanks and best regards

Jim Anthony November 16, 2018 at 9:03am

Hi Jim,

No problem, our 20mm engineered oak flooring would be perfectly fine for this situation. As for fixing, we would typically recommend secret screwing using Spax 3.5 x 55mm Screws.

Hope this helps

Peak Oak November 16, 2018 at 9:16am

I intend on laying an engineered oak floor directly on top of existing joists.
I’ve seen above the method of fixing I’m just curious I’ve there would be a problem secret fixing the boards on a 45 degree angle through the “tongue” of the board on each row, instead of having nail head/plugs on show?

Michael January 25, 2019 at 3:43pm

Hi Michael,

The surface fixing method you refer to is for solid oak boards which are 160mm or wider. This is because of the susceptibility to movement with wider solid oak boards.

For engineered oak boards, this surface fixing method would not be required. The secret fixing method of fixing through the tongue of the board would be sufficient.

Hope this helps.

Peak Oak January 25, 2019 at 3:47pm

Can 20mm engineered wood be floated over joists (with underlay) or should it be screwed/nailed? We have a 50mm screed between the joists for the UFH but this is only on Celotex/battens so is not structural.

Rob March 15, 2019 at 11:08am

Hi Rob,

When laying over underfloor heating systems we would never recommend floating an oak floor. Engineered oak flooring should be directly fixed (gluing or screwing) over underfloor heating, rather than floated.

Hope this helps

Peak Oak March 15, 2019 at 11:11am

I'm planning to fix 20mm engineered oak T&G boards directly to the joists. My joists will be oversize for the span in order to allow enough depth for battens, celotex and biscuit screed (for ufh). The span tables allow a spacing of 600mm for the joists, but will this spacing be ok for the 20mm floorboards? the room is a kitchen diner. I'll be ordering the joists in the next few days.

Paul August 14, 2019 at 4:14pm

Hi Paul,

When fixing onto joists, our recommendation for our flooring would be lay the joists at 450mm centres. This typically allows the insulation to be cut into thirds to fit between the joists.

Hope this helps

Peak Oak August 14, 2019 at 4:32pm

Thanks for the prompt reply. Yes, that makes sense regarding the insulation. If I do decide to go with 600mm centres can I assume that this is ok regarding the strength and flexibility of 20mm engineered oak boards?
Am I correct in assuming that I can mitigate the risks from any liquid spillages by using a waterproof glue on all joints.
Regards, Paul

Paul August 15, 2019 at 8:49am

Hi Paul,

It would be possible to lay the flooring at these centres. The point to consider is that because of the increased distance, you may find there is more "spring" in the floor in comparison to 450mm centres.

As for glueing the joints, as you are laying over an underfloor heating system, this is something we would definitely not recommend. The risks of liquid etc. is more down to the quality of the oak flooring finish.

Peak Oak August 16, 2019 at 2:53pm

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