Levelling uneven joists

[pavsid]

Hi all, I'm replacing some floorboards which were damaged and sloping. The reason they are sloping is because a couple of joists in the middle of the room seem to have sunk in the middle.

So I'm trying to find the best way to pack them out and achieve a flat finish. I've been looking at strip wood but that only seems to come in minimum 6mm thicknesses, and the joists are out by about 4-5mm.

I've also been reading on here about firring (or furring) strips, but again can't seem to find anything online for the thickness I need.

Any advice? I have a planer by the way, if that's gonna help?

 

[oldbutnotdead]

First off- any visible reason why those particular joists have sagged. Are the ends rotten or this there worm in them? To be honest, 5mm isn't a drop I'd be getting stressed about....

2 choices;
1 Use cardboard or DG packers to varying depths across board width across each saggy joist. This is fine for 1 or 2 boards across 2 or 3 joists but will get really boring for a long run
2 Get some straight lengths of 3 x 1 or 3 x 2 (or even 2 x 1 would do for 5mm drop) that are long enough to bridge the sag. Fix them frequently (100mm centres) to the side of the saggy joists so the top edge is level with the top of the non saggy joists.

 

[ree]

As above (altho i wouldn't use paper packers).

You must find the underlying cause - have you ever been under the floor and examined the joisting?

Is there any movement in the two sagging joists or the nearby joists?

 

[big-all]

yes packers or rip down hardboard [3.2mm] ply[ 5.5mm] mdf [6mm] into strips

 

[pavsid]

Hi all, thanks for your replies.

I've done some further investigating, and took up some more floorboards. The two joists in question are actually up to 15mm out - and that's at the end of their run where they sit on a supporting wall below. That got me worried, but looking at the wall below (which is actually a doorway with a lintel above) it looks like the lintel has sagged somewhat, but not as much as 15mm. I've not been able to see where the difference is, but as the wall & lintel below seem to be in otherwise decent condition, i'm guessing this is just down to normal settlement?

As the joists are so far out, i'm guessing the best approach is to screw some 3x2 to the side of the joists to make them level.

Should I be more concerned about the wall/lintel below?

 

[ree]

Why not post pics of the joists above, and the lintel area below?

 

[oldbutnotdead]

It would be wise while you're at this stage (of presumably room empty and moderate damage permissible) to have a look at the ends of the joists where they go into the wall and the brickwork in that general area. Assuming the joists are in pockets in the wall, see how much fresh air is between the joist top and the top of the pocket, also see how deep the joist is into the pocket and what the joists are supported on (usually gash bits of timber that may have dropped out or rotted that may be your problem).

Are you sure there's a lintel above the doorway? And if there is a lintel, is it on decent bearings and is the lintel itself in good order. Any sign of this 15mm movement from outside?

There are all sorts of things that could be going on here- well worth a look and some pics (and run a straight edge across and up the area as well)

 

[pavsid]

Hi folks, OK, here are some photos. You can actually see the sag in the first photo, but the second photo is from the other side of the door and there doesn't appear to be any sag.

There are no signs of cracking anywhere.

 

[oldbutnotdead]

Looking at those, I'd be suspecting there's no lintel or not much of one above that doorway- the frame doesn't look that beefy but the 'drop' is on the inner skin of the wall where the frame isn't and timber is quite good at supporting dead load (much better than PVC). 15mm is quite a lot across 1900 mm or so

Hard to tell for certain- is that double doorway original or has a single door or window been enlarged for a conservatory/extension addition at some stage? Have you already fixed 3 x 2 along the dropped joists? (pic 3)

Difficult to determine presence or absence of lintel without knocking plasterwork off, you could try drilling with a long 3 or 4mm masonry bit and see if you hit metal, timber or concrete under the plaster. Or try a stud detector. End of the day, if it has been there for a while and not cracked then whatever structure is in there is probably going to stay there unless you do something major to disturb it. Me, I'd like to know.......

 

[pavsid]

Looking at those, I'd be suspecting there's no lintel or not much of one above that doorway- the frame doesn't look that beefy but the 'drop' is on the inner skin of the wall where the frame isn't and timber is quite good at supporting dead load (much better than PVC). 15mm is quite a lot across 1900 mm or so

Hard to tell for certain- is that double doorway original or has a single door or window been enlarged for a conservatory/extension addition at some stage? Have you already fixed 3 x 2 along the dropped joists? (pic 3)

Difficult to determine presence or absence of lintel without knocking plasterwork off, you could try drilling with a long 3 or 4mm masonry bit and see if you hit metal, timber or concrete under the plaster. Or try a stud detector. End of the day, if it has been there for a while and not cracked then whatever structure is in there is probably going to stay there unless you do something major to disturb it. Me, I'd like to know.......

That what you see there above the doorway is the actual concrete lintel (or whatever it is) - there's no plaster there.

We only moved in a year ago so don't know the history but looking at the paint around I'd think it's been a doorway for quite some years.

Yes I've screwed 3x2s to the sides of the joists to level them out - it's worked a treat, and so much easier than nailing stripwood to the top of the joists and planing down like I was planning on doing!

Problem now is that the ceiling below is gonna need levelling out too before we board over it

Thanks for all your help, will keep an eye on the "lintel" and cross that bridge if it moves any further.