How do I fix bouncy joists & splitting T&G Floorb

[davidn1]

Hi All

Looking for some ideas to sort a problem with a 20 year old ground floor extension combined Kitchen and dining area floor.

Floor details
Floor size 29f 6 inch by 10f 6 inch
Room split with a breakfast bar with 2 legs so a light load
19 mil TG floorboards stained and varnished running the length of the room
all (sanded at least twice so thinner now)
Floor joists running the width of the room are 9 by 2 at an estimated length of 10f 8 inch with a centre to centre gap of 23 inch.
There is only 1 noggin in the centre of each joist
There is a vapour barrier stapled to the under side of the joists with insulation laid on top

The problem is that there is a lot of movement in the floorboards when you stand on them especially between the joists so much so that some of the boards have split along the TG with the upper part of the grove snapping off this is not helped by the fact that the boards have about a 5 mil gap between all of them and there is a noticeable bounce in the joists.

I did replaced about 6 boards last year as a temporary fix but more boards are starting to go so as a result I'm going to be doing a kitchen refurbishment next year as there is a long list of problems with this kitchen things like there was no separate ring main installed for the kitchen and units and worktops are not installed properly and its time I got it sorted.

I know that the floor movement is mainly caused by the floorboards being over sanded and by the poor joist spacing with this in mind I have a number of options to strengthen and repair the floor listed below that I would be grateful for you feedback on or if you have an alternative idea please let me know

Option 1
Remove all floorboards
Level the joists (at least 2 are high)
Remove centre noggins and glue and screw another joist to the old joist
Install 2 new noggins spaced evenly over the length of the joist
Relay new floorboards

Option 2
Remove all floorboards
Level the joists by removing about 18mm from the top of each old joist
Remove centre noggins
Glue and screw another joist to the old joist
Install 2 new noggins spaced evenly over the length of the joist
Board the floor with 18mm plywood sheets
Then relay new floorboards on top

I could lay laminated flooring instead of T&G floorboards and remove lees material from the top of the old joist but I’m not sure laminated flooring would be a good idea in a kitchen?

Option 3
Remove all floorboards
Level the joists
Remove centre noggins
Install new joist in-between the old joist
Install 2 new noggins spaced evenly over the length of the old and new joist
Relay new floorboards

Also
Any tips on how best to insulate the floor
And to minimise shrinkage/movement in the new floorboards and gaps appearing between the floorboards do they have to be stored in the same room they are going to be installed in or just in the house?

Thanks in advance
David

 

[davidn1]

Any thoughts on the best way to fix this ?

Cheers
David

 

[masona]

Do you know what the joist centre measurement is, normally 400mm / 16" centre.

Joist size?

what is it resting on, sleeper wallplate? and how far apart etc ?

Any sign of rot?

new or old timber?

 

[big-all]

have i read this correctly your joist are at 23" centres and your flooring is 17mm

you need probably 8x2" joists at 400mm centres and idealy 20mm flooring definatly 18mm minimum

 

[davidn1]

Hi

The joists are 2” by 9” and are 23” centre to centre
Don’t know how much space there is under the length of the joists as the vapour barrier is in the way
There’s 1 noggin in the centre of each joist
No signs of previous damp problems or rot
I don’t know how they are attached to the wall as all the information I have is from notes I took when I did the temporary repair

I'm thinking the best option for the joists would be

Remove all floorboards
Repair any lose or damages joists and level them all
Remove centre noggins
Install new 2” by 9” joist in-between the old joist giving a centre to centre joist spacing of 11 ½”
Install 2 new noggins spaced evenly over the length of the old and new joist

Insulating
At the moment there is a vapour barrier (polyethylene sheet) stapled to the under side of the joists with fibreglass insulation laid in-between the joists and supported by the VB. After installing the new joists my intention is to keep the installed vapour barrier (if undamaged) and pack on top of the VB and in-between the new and old joists with fibreglass insulation.

Would this be expectable or should I replace the polyethylene sheet vapour barrier with netting stapled to the under side of the joists and then install the fibreglass insulation on top of the netting

Or would I be better using something like celotex solid insulating boards laid between the joists?

The floorboards are now about 15mm thick due to sanding by us and the old occupants.
As a result I’ll definitely be replacing all the T&G floorboards or boarding and installing laminated flooring.
As I'm still unsure as to the best option anyone got any feedback on using laminated flooring in a kitchen

Thanks again
David

 

[ajrobb]

Your mention of a vapour barrier under the insulation sounds all wrong. What little I've read and talked with local building control suggests mineral wool insulation should be held in place with netting and no vapour barrier. Spills should be allowed to drain right through.

 

[drummerbod]

Hi

Insulating
At the moment there is a vapour barrier (polyethylene sheet) stapled to the under side of the joists with fibreglass insulation laid in-between the joists and supported by the VB. After installing the new joists my intention is to keep the installed vapour barrier (if undamaged) and pack on top of the VB and in-between the new and old joists with fibreglass insulation.

Would this be expectable or should I replace the polyethylene sheet vapour barrier with netting stapled to the under side of the joists and then install the fibreglass insulation on top of the netting

Or would I be better using something like celotex solid insulating boards laid between the joists?

Thanks again
David

Vapour barrier should not exist. Replace with something like chicken wire mesh.

Celotex board is very expensive and in this instance not required. Stick with normal wool\fibre insulation.