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Expansion gap - solid oak flooring - cork strip

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Nordic Pine
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Is cork strip OK to put in an expansion gap for solid oak flooring? I have done so, but having second thoughts. Cork compresses under pressure, but it doesn’t compress to zero, so it must be equivalent to reducing the size of the expansion gap.

I’ve left 1/2” gap all the way around the floor. The cork strip is also 1/2” and sold specifically for putting in expansion gaps including for solid wood floors. The wood is well acclimatised, being in the space for 14 months before laying. The floor is laid directly on top of existing floorboards and is floating - no fixings, no sticky underlay.

The motivation for putting the cork in was to provide just enough constraint on the floor that walking on it wouldn’t open gaps or cause it to shift.
 
When I install solid wood flooring of the tongue and groove variety it is always nailed down with an expansion joint at walls which is covered by a shirting board.
If using an engineered hardwood flooring which locks together there is no movement but I do leave a small gap at the walls.
You are defeating the purpose of an expansion joint by filling it with cork, with seasonal humidity changes the floor can expand and buckle and shrink and leave more than desirable gabs at the joints.

Are you using engineered hardwood flooring or a locking type of solid wood flooring?
 
I’m using solid European oak 20mm thick x 187mm wide tongue and groove, no interlocking (slight friction between tongue and groove). Laid directly over an existing wooden floor.
 
What are the install instructions for the floor?
There usually is a slight friction fit.
I understand your reasoning for the cork , is it a large area you have?
Does the cork manfacturer state the amount the cork can be compressed and will it swell back to normal size after the floor boards have contracted?

I have never used the cork expansion product maybe someone on this site over your way has experience with it and will hopefully chime in.
 
These are the install instructions from the supplier: https://www.britishhardwoods.co.uk/media/flooring-guide/Hardwood-Floor-Fitting-Guide-2021.pdf

They talk about floating a floor over adhesive sheet on a solid subfloor, so I’m going off script a bit.

Recognising this, I’m fine with gaps opening up and having to adjust later, but I definitely don’t want gaps at the wall completely closing or permanent damage.

The strips are these: https://www.wickes.co.uk/Vitrex-Expansion-Cork-Strips---Pack-of-18/p/922302#

Available from multiple retailers. The manufacturer site doesn’t have much info.

The area is about 20 boards wide.
 
Welcome back....long time no see !

It's an excuse to buy a multi-tool like a Fein or a Bosch. Place a floorboard offcut plus a 2mm spacer for wiggle room against the skirting board and run the Fein along thus cutting a strip off the skirting board. That means you can slide the floorboard underneath.
 
RogerS said:
Welcome back....long time no see !

It's an excuse to buy a multi-tool like a Fein or a Bosch. Place a floorboard offcut plus a 2mm spacer for wiggle room against the skirting board and run the Fein along thus cutting a strip off the skirting board. That means you can slide the floorboard underneath.
Click to expand...
Watching out below any plug sockets, etc ...
 
Thanks Roger! I recall you’re not a fan, but I’ve already got scotia cut and ready to attach. The cork won’t be visible (if it stays). I did undercut the architrave at the door, but I used a ryoba and chisel for that. (I have a Bosch green multitool, but I don’t really get on with it - maybe I keep using the wrong cutters or some other form of user error.)
 
Many, many years ago I used cork expansion strips like yours around a parquet floor in a conservatory. The floor moved so much it compressed the cork and moved the wall of the conservatory.

I always leave my expansion gaps completely clear for expansion now! If you think about about it, a 20mm cork filled expansion gap isn’t a 20mm gap because it only allows about 6mm and a solid oak floor will probably move more than that.
 
Thanks for the direct experience, Stuart. Think I’ll ditch the cork before I put the scotia on.

While we’re on the subject of expansion gaps, what size hole are you all putting around 15mm radiator pipe? The British Hardwoods instructions says drill a 20mm hole. But isn’t that only equivalent to a 2.5 mm expansion gap? I’ve gone for 32mm holes.
 
This has always perplexed me. Solid Oak t and g and screwed down to a plywood base stays put, yet the forces are still there, where do they go, or are the movements small enough that they can be contained? Perhaps it’s because a lot of our guidance and knowledge comes from countries that experience vastly greater movement, perhaps the same floor screwed to the same 18mm ply in Southern America would be buckled up like an upturned ship.
Yes you can use an adhesive sheet like Elastilon, and it will keep the boards tight together but it can expand as a very wide piece of wood, whereas screwing with those thin floorboard screws through the tongues at an angle will give a floor that pretty much stays where you put it. Especially as you have acclimatised the wood so well.
 
Cabinetman said:
This has always perplexed me. Solid Oak t and g and screwed down to a plywood base stays put, yet the forces are still there, where do they go, or are the movements small enough that they can be contained? Perhaps it’s because a lot of our guidance and knowledge comes from countries that experience vastly greater movement, perhaps the same floor screwed to the same 18mm ply in Southern America would be buckled up like an upturned ship.
Yes you can use an adhesive sheet like Elastilon, and it will keep the boards tight together but it can expand as a very wide piece of wood, whereas screwing with those thin floorboard screws through the tongues at an angle will give a floor that pretty much stays where you put it. Especially as you have acclimatised the wood so well.
Click to expand...
I agree entirely re expansion gaps Ian. And using Tongue-Tite screws
 
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