Levelling upstairs floor joists

max 73

hi guys,

anyone know how to level the floor joists in an upstairs bedroom? or do i have to get in a professional?

cheers

antiskeptic

max 73 wrote: »

hi guys,

anyone know how to level the floor joists in an upstairs bedroom? or do i have to get in a professional?

cheers

What are you planning on putting down when it's level? Sheet plywood would mean it's a reasonably straighforward (if somewhat detailed) job. If wanting to put down floorboards though then it'd be a fair bit more complex.

max 73

just plywood, carpet going back down

Carpenter

How bad are they ATM pic might help

antiskeptic

max 73 wrote: »

just plywood, carpet going back down

Fair enough.

I'm assuming a square or rectangular room without chimney breast or other protrusions. You'll need three straight edged boards: one spanning the room diagonal, one the width and one the length. Kickboard would be good as it doesn't sag under it's own weight when held edge down

You'll also need a level, some packing wood (thin plywood 1/8" or thinner cut into squares about the width of a joist on a side, some panel pins (1 - 1.5"" should do), some short, flat topped screws - perhaps 5mm diameter chipboard screws, a (say) 3mm drill and a battery screwdriver and a savvy assistant.

In the 4 corners of the room, a couple of inches in from the skirting, drill a vertical 3mm hole in the middle of the joist. Screw a screw in until it's about 1/2" proud of the surface. Get them straight.

Place the diagonal board across a diagonal pair of screws (let's call them screw 1 and 2) and set your level on it. Adjust the screw at whichever end needs it to get a level - bit by bit. Don't touch these screws 1 and 2 until further notice.

Now place the length board from one of these two corner screws (let's say screw 1) to the screw length-opposite (screw 3) and adjust screw 3 until you get a level. If you've been precise, a board placed between screw 2 and 3 will also be level. So check that it is with the width board. Repeat the length board between screws 2 and 4 adjusting 4 until you get a level. Check between 4 and 1 with the width board.

Now you know all four corners are on the same flat plane.

Place the diagonal between screws 1 and 2 again and inspect the gap between it and the joists underneath all the way across. Is there space bwtween it and every joist? If so, then you need to lower the screws - all 4 of them - and all by the same amount. Repeat this bit by bit until the diagonal across 1 and 2 just touches a joist somewhere across it's span. Now check the other diagonal and the lengths and the widths to see you haven't gone too low. You're too low if any of the other boards fails to rest on it's screws due to contact with a joist - in which case wind all 4 screws back up a bit

It's a slow process but you'll end up with level reference points.

Is it understandable so far?

max 73

Carpenter wrote: »

How bad are they ATM pic might help

on closer inspection there's a bit of a bad dip alright particularly in one area, i'll have to put a straight edge across the whole floor area and dip to see how bad it actually is (a hairline crack in the ceiling underneath is getting bigger)

these are obviously connected

the room is about 3.00m x 3.00m

worst case i may have to get in a carpenter to correct the joist problem (flooring and ceiling replacement i can do)

max 73

antiskeptic wrote: »

Fair enough.

I'm assuming a square or rectangular room without chimney breast or other protrusions. You'll need three straight edged boards: one spanning the room diagonal, one the width and one the length. Kickboard would be good as it doesn't sag under it's own weight when held edge down

You'll also need a level, some packing wood (thin plywood 1/8" or thinner cut into squares about the width of a joist on a side, some panel pins (1 - 1.5"" should do), some short, flat topped screws - perhaps 5mm diameter chipboard screws, a (say) 3mm drill and a battery screwdriver and a savvy assistant.

In the 4 corners of the room, a couple of inches in from the skirting, drill a vertical 3mm hole in the middle of the joist. Screw a screw in until it's about 1/2" proud of the surface. Get them straight.

Place the diagonal board across a diagonal pair of screws (let's call them screw 1 and 2) and set your level on it. Adjust the screw at whichever end needs it to get a level - bit by bit. Don't touch these screws 1 and 2 until further notice.

Now place the length board from one of these two corner screws (let's say screw 1) to the screw length-opposite (screw 3) and adjust screw 3 until you get a level. If you've been precise, a board placed between screw 2 and 3 will also be level. So check that it is with the width board. Repeat the length board between screws 2 and 4 adjusting 4 until you get a level. Check between 4 and 1 with the width board.

Now you know all four corners are on the same flat plane.

Place the diagonal between screws 1 and 2 again and inspect the gap between it and the joists underneath all the way across. Is there space bwtween it and every joist? If so, then you need to lower the screws - all 4 of them - and all by the same amount. Repeat this bit by bit until the diagonal across 1 and 2 just touches a joist somewhere across it's span. Now check the other diagonal and the lengths and the widths to see you haven't gone too low. You're too low if any of the other boards fails to rest on it's screws due to contact with a joist - in which case wind all 4 screws back up a bit

It's a slow process but you'll end up with level reference points.

Is it understandable so far?

ya, i see what your doing (where the straight edge first touches the top of a joist - that is my datum level where all the levelling will be done from??)

antiskeptic

max 73 wrote: »

ya, i see what your doing (where the straight edge first touches the top of a joist - that is my datum level where all the levelling will be done from??)

That's about it - that first joist contact and the 4 screws are all at the same level. You'll probably find yourself a little low and having to raise the screws a bit after checking with the other boards. The point is to achieve a level plane that isn't too high above the highest point of the floor.

After that it's a question of spanning the diagonal between 1 and 2, inserting/pinning packing squares to fill the gaps between edge and joists. Then repeating for the other diagonal, the 2 lengths and two widths. You've now enough points filled to span in other ways and add more packing.

I imagine you'd want packing every foot or so along a joist - with longer packing strips to sit half/half under adjoining plywood boards. If I was doing it, I'd also add a dab of glue to each packer and between packer and joist to eliminate the chance of squeaking.

Seeing as your room is square you can do with just a diagonal and a length.


(From your other post it might be that your floor is really sagging in which case you either repair or insert something more stable that packers - it isn't intended that you pile 1/8" squares of plywood to accomodate a 2" drop )

max 73

thanks lads, i'll keep ye posted as to how things are going, thanks again

Carpenter

If you are stuck and are close to me I can have a look (No Charge)

max 73

thanks carpenter but i'm in cork

Carpenter

max 73 wrote: »

thanks carpenter but i'm in cork

CORK :eek: pics will have to do so LOL

Buford T Justice

Why are the Joists sagging so much though?

max 73

Fingers McGee wrote: »

Why are the Joists sagging so much though?

don't know but looking at it to try to find why, if it can be repaired by me or is it a bigger issue? hope it's the former

antiskeptic

max 73 wrote: »

don't know but looking at it to try to find why, if it can be repaired by me or is it a bigger issue? hope it's the former

Are the joists actually bending in the middle (which would seem a little strange given the small size of the room) or are particular joists dropping in one area of the floor?

Buford T Justice

antiskeptic wrote: »

Are the joists actually bending in the middle (which would seem a little strange given the small size of the room) or are particular joists dropping in one area of the floor?

Most serious is the Joists are rotting or you have a serious case of woodworm and deathwatch beetle.

How old is the house?

10-10-20

Or the load is excessive, or the joists are the incorrect width, or there is excessive moisture on the joist.
There could be more to this than meets the eye!

max 73

a quick update.....

on sat afternoon a portion of the ceiling collapsed :eek: (turns out its a lath & plaster ceiling so me thinks the problem is now going to be quite BIG) - thank god none of us were underneath it, especially our 2 yr old

i have a builder coming today to look at it

i'll upload a few photos later along with builder's opinion

fingers crossed that it's not a serious as i fear it may be!!

Buford T Justice

max 73 wrote: »

a quick update.....

on sat afternoon a portion of the ceiling collapsed :eek: (turns out its a lath & plaster ceiling so me thinks the problem is now going to be quite BIG) - thank god none of us were underneath it, especially our 2 yr old

i have a builder coming today to look at it

i'll upload a few photos later along with builder's opinion

fingers crossed that it's not a serious as i fear it may be!!

Some pics would be good.

If its a lath and plaster ceiling then its old, and so the joists would be older. At a guess, they could be past their sell by date and need replacing....

max 73

Sorry for not updating sooner

Stripped existing ceiling & floor to find that some of the existing joists were loose in the brick pockets of the wall and were crumbly.

So I retro fitted new joists to all existing joists and put in a row of bridgers along with 18mm wbp floor with a new plasterboard ceiling.

The job was dirty, tough but is now painted and back to normal, the week was hell as we had to move out for a few days & worked lonnng days but alls ready for Santa.

Thanks for all the advice lads & happy holidays to all