Lately we’ve seen (DIY) forum posts, questions in our own inbox and even results by diy-ers and builders alike, about (and in the results missing): not leaving enough expansion gaps when installing wooden floors
Most know about gaps and leaving them around the perimeter of the floor – using the simple rule of thumb: 3-4mm per meter width of the room with a minimum of 10mm – but then go wrong at certain points in rooms or hallways.
You have to leave an expansion gaps ALL AROUND the perimeter of the whole floor, not just here and there or where you can cover the gap with skirting boards.
If you don’t have a sufficient wide expansion gap at one single place, like a doorpost or in front of the fireplace or staircase, all the other wide enough expansion gaps are rendered useless! You wood floor is not going to think: Oh, there’s not a gap so I won’t expand there. Believe me: it will!
A wood floor, specially a solid wood floor, will expand evenly. Most of the times that is: when it is stuck at one certain point it can’t and will raise its level at or around the point that is blocking its normal movement. For instance when glue has dripped out of the T&G and sticks the wood floor to the underlayment.
Or when you haven’t undercut your doorpost or laid the floor flush against the side of a fireplace or staircase. Reasons we heard: skirting board doesn’t reach that far; don’t know what to cover the gap with around the fire place or I don’t like to use a divider between the rooms where the wood floor is installed in two different directions anyway.
We cannot change the laws of physics – it’s as simple as that!
Leave expansion gaps all around the perimeter, there are various solutions – proper and aesthetically pleasing solutions – for all situations:
* Doorposts: undercut architraves and doorpost with handsaw as far as the height of the new floor and chisel out what is needed – making sure you chisel out enough for the floor to hide its edge and still have room to expand
* Fireplace: leave an expansion gaps around and when the floor ends lower pin down a flat solid beading on the floor – covering the gap in a neat and almost flush-way. When your floor ends higher use a so-called End-threshold to finish it off: giving you both the needed expansion gap as a neat very small ‘step’ from floor to fire-place.
* Stair: if the stair carpet isn’t thick enough to cover the gap (most professional carpet fitters will ‘double-back’ the carpet at the bottom of the stair, giving you twice the thickness of the carpet) you either install a flat beading on the floor or use mastic filler (curved stairs come to mind). In some (rare) cases you could even fill the gap with a cork strip – as long as you can reach the strip to lift it out when the floor threatens to expand!
Leave gaps everywhere – as said before: we mere mortals cannot change the laws of physics!
Don't use cork strips to fill your expansion gaps!
Some issues keep recurring: cork strips among them.
A few days ago we received the following email:
"I realise the importance of leaving an expansion gap around a wooden floor (oak parquet in my case) but can you tell me why we are told to insert cork strips around the edge? Surely the cork is only taking up valuable expansion room. Is it ok to just leave a 10mm gap all around?"
This was our (recurring) answer on this subject:
Thank you for your question. We are trying so hard do tell everyone exactly that: DON'T use cork strips to fill the expansion gap.
These were used many, many years ago to divide design parquet pattern and the block border and somehow ended up in the expansion gap.
So, you are absolutely right. Leave your expansion gap 'empty' to cater for any natural seasonal movement of your wood floor."
Many thanks, it's nice to be right for once!
Of course he was right, we still don't understand how the old-fashion cork divider strip ended up as recommendation to fill your expansion gaps.