Joist Levels on Suspended floor

6 Jun 2008
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United Kingdom
So have I opened a can of worms. In a nut shell I am planning to have a parquet floor installed in my lounge. Its a suspended floor which seems very solid and dry. However even though the boards are in good condition the plan is to lift these and install new flat and level chipboard or ply to create a level surface for the
new floor.

Having lifted a few of the boards I have noticed a few a few issues.

1. From left to right the joists are not level. They seem to be higher in the middle with a drop of around x to the left.

2. The joists are resting on sleeper walls, whose mortar seems to be crumbling.

So my questions are

1. Can I just screw and glue the new chip board as is.. will this create any major issues to the new floor.

2. Should I sister the old joists

3. Should I be building new sleeper walls and installing new joists.. if I do this would there be old footings or something I can lay the new bricks on.

Would appreciate a few ideas and thoughts.

I have attached some pics
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Just a diy response here...
The sleeper walls look ok to me - I can't see them going anywhere, so I wouldn't worry. The joists look dry and sound.
I'd be inclined to use packing pieces under the joists to level them up.
If you have the height to keep the floorboards in and lay the board on top, then do so - it's less work, less damage and will be stronger.
Once you've finished, accessing the void would be a bit tricky, so if you ned to check underfloor vents or run any cables that you might want at a later date, now would be a good time to do so.
Sadly I can't lay board on top as the height will exceed our fireplace hearth.

I am thinking about packing.. would that be strong enough. What type of wood should I use.. or should I use some plastic shims or something.
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Packing shims should be fine, screw through them into the joists if you can.

..would these work.

.are they OK to lift the joist by 1cm or more
In theory they are non-structural, i.e they are designed for items such as window boards door casings, etc. Under load they can compress, especially the rectangular glazing packers which are made from a more brittle plastic and have recess on the underside. At work we are supposed to use hardwood shims or folding wedges to meet the requirements of the BCO. If using any packers in a load bearing situation do make sure that they are made from solid material with no voids (in other words the horseshoe type are more suitable). Try to avoid using big packs of them shims and use the minimum number of shims you can - a single 10mm or 2 no. 5mm Is much more stable than 10 no.1mm shims - and if you exceed 10mm consider cutting thickers from either hardwood or exterior grade plywood.
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My preference for packing between joist and wall plate is either solid timber or plywood.


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