Advice please - Solid Oak flooring direct on joists

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Hi,
I am hoping to get some advice:

I would like to have solid oak (20mm) flooring installed in a bedroom directly onto the floor joists. I don't want to put down a chipboard floor first as the house is old and has restricted head height.

Have spoken to a few flooring supply shops and whilst most said there would be no problem (as long as the wood is left for 2-3 weeks to acclimatise and that a gap is left around the outside), one shop plus one builder have said that they shouldn't be installed directly onto the joists.

Has anyone got any information that may help?

Cheers
 
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i wouldn't advise it. You can get load bearing floors which its o.k to do it with but i like to put down plywood 18/22mm first. Main reasons being- if you get crooking in the planks while fitting you can get a gappy floor. Also you can get alot of bounce across boards where ends of planks dont hit joists if fitting random plank. You will also get draughts through joints if not a tight tongue and groove. I dont think 18mm extra height should cause you much problem. Get people to take there shoes off, this should bring your height lower :LOL: . And dont use chipboard, when you nail into this it tends to blow a large hole in the back of it causing cleats/nails to work loose making your floor unstable. You should also check air bricks under floor that they are clear and correct amount of air flow is present. And yes you must acclimatize floor for at least 3-4 weeks if you dont have wood moister testing equipment and expansion of approx 18mm around all walls and under door frame is needed on a room approx 4-5 meters wide.
 
Rather different opinion here, Matty, sorry.
Draft on second floor will be much lesser than on first floor (presuming that bedroom is on second floor?). Also T&G will cancel most of the draft if the board shrinks. Only item to really check is the distance between joists: not wider than 30 - 35 cm otherwise the boards may bend and wobble.
Minimum thickness of floorbards is 18mm so 20mm should not be a problem. Use thick enough nails (50 - 60mm).

Proper quality floorboards acclimatise within 4 - 5 days. Minimum expansion gap of 10mm, plus 3mm per extra meter if room is wider than 3 meter (4 meter wide = 12 - 13mm gap)

For other info see this FAQ blog post
 
true, if fitting above ground floor the draft/air brick part is not as important but dont agree on the acclimatizing in bit. Sorry woody! For instance if the house contains a high moisture content and lets say the joists sit at a moister level of say 14% and the floor you buy has been stored in a area of low humidity, the floors moisture content is lets say 5% there will be a few weeks for the new floor to take in the moisture and stabilize. But like a said if you have a meter to take the readings between the joists and the new floor and they are within 4% of each other you can lay the floor when you want. Guess you wouldn't have a meter tho so i would be safe and leave for as long as possible to acclimatize.
 
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Thanks so much for the very helpful replies. : :D

I now think I know what we should do. I'll discuss with my wife and post what we decide to do and how it works

Thanks again.
 
Just to add on, if the floor do bounce then put in herringbone structure or straight noggins and if some of the joists is high or low using a straight edge then pack with timber fillet or shave it off with a plane
 
Both make good points. I advise asking the manufacturer or supplier how long the product should aclimatise. Acclimation can take a minimum of 7 days for solid wood that is prefinshed to 3 weeks for unfinished. Make sure you leave the expansion gap as suggested by woodyoulike. 14% moisture content in joists is OK but I would always recommend sisalkraft paper (building paper with bitumen backing) when installing any solid wood strip or plank to help prevent moisture causing problems. The 4% difference between subfloor and wood is a good rule but if you do get a floor dried to 5% moisture I would be concerned. Normally manufacturers dry wood to 8% - 10% in UK with 6% for underfloor heating, at 5% your floor will need more than 10mm expansion and cause problems when seasons change. Your main problem is spacing between joists, 30 - 35mm centres are required any wider and movement can cause problems with fixings. Use 50mm nails minimum as suggested. Your supplier should be able to give you all the advice you need and supply the manufacturers installation instructions. Good Luck
 
Thanks again for the advice.

I have measured the gap between joists - it is 40mm, not the 30-35 that is recommended :(

Your advice shows that this may be a problem (with bounce and fixings coming loose). How can this be overcome?
 
Your boards are 20mm thick so you might get away with it. How wide are your boards?
Make sure the every board connects with at least 3 joists.
 
No, these widths are fine. If in doubt, you could add some small battens to the joists first to narrow the gap.
 

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