Sparse paneling on unreasonably uneven rafters - disaster

[Rumpnissen]

Hello,

In our summer cottage, I am currently renovating the upper floor and have now reached the sparse paneling in the sloping roof.

The plan is OSB + plasterboard on the ceiling and walls.

The problem is that the rafters on which I am mounting the spars are extremely uneven, with a difference of about 35mm between the highest and lowest points, and the difference is also between the top, bottom, and middle, and everything in between on each rafter. From 0 to around 20mm up and down.

I am using a straightedge to measure back and forth and crisscross, and I also have a laser, but it doesn't help much due to the optical illusion caused by the roof angle. I've also tried setting the laser on a tripod and locking the line at 40 degrees (roof angle), but it's entirely impossible to keep the laser consistent along the entire length of the house without it drifting away.

I have shimmed and used adjustment screws, but I can still have differences between various sparse boards AND/OR between different points on the same board, possibly up to 3-4mm. Fixing one point affects another, and nothing aligns again. I'm starting to get tired.

My question is...

How tolerant is OSB to an uneven surface? Can this be fudged with the boards?

Reply to:
Frustrated_amateur_soon_without_hair

 

[Rumpnissen]

Hello,

In our summer house, I am currently renovating the upper floor and have now reached the lathing in the slanted ceiling.

The plan is OSB + drywall on the ceiling and walls.

The problem is that the rafters on which I mount the lathing are extremely uneven, with a difference of about 35mm between the highest and lowest points. But there is also variation between the top, bottom, and middle, and everything in between on each rafter. From 0 to around 20mm up and down.

I go with a straightedge and measure back and forth and crosswise, and I also have a laser, but it doesn't help much due to the optical illusion caused by the roof angle. I've also tried placing the laser on a tripod and locking the line at 40 degrees (roof angle), but it is completely impossible to get the laser to consistently follow along the entire length of the house without deviating further away.

I've shimmed and used adjustment screws, but I can still have differences between different laths AND/OR between different points on the same lath, maybe up to 3-4mm. Fixing one point affects another, and nothing aligns again. I'm starting to get tired.

My question is...

How tolerant is OSB to uneven surfaces? Can this be fudged with the boards?

Reply to:
Desperate_amateur_almost_bald

In hindsight, I obviously should have screw-glued the studs along with the old rafters and created new lowest levels, but that will have to wait until next time...

 

[fribygg]

In hindsight, I should have glued and screwed battens along the old rafters and created new lowest levels, but that'll be for next time..

How quickly you figured it out after the fact, for some of us it usually takes a week before we realize how we should have done it.

 

[Rumpnissen]

How quickly you became wise after the fact; for some of us, it usually takes about a week before we realize how we should have done it.

Well, I realized I should have done it when the fabric was already up, and I started with the first slat, but I couldn't be bothered to tear it down and especially tape everything again. A really tedious job to tape around all the support legs and collar beams.

All the slats are up now, and it's quite evenly done, but in some places, I really can't do it any better.

Hence my question.

 

[Dr Benz]

Can't you release the glesen and shim under the screws? That way you'll get the same holes but straighter gles? Tighten a string from end to end since the laser doesn't seem to work as well in this case.

 

[fribygg]

Can this be cheated with the boards?

No, if the surface is that uneven, you'll either have to redo it or use a panel ceiling, it's more forgiving.

The plan is osb + plasterboard in the ceiling and walls.

Why osb in the ceiling?

 

[Rumpnissen]

Can't you loosen the battens and shim under the screws? That way, you'll have the same hole but a straighter batten. Stretch a string from end to end since the laser doesn't seem to work as well in this case.

I have some shims of various material underneath where needed. String is a good idea. Haven't even thought about it. Will check tomorrow, the train hasn't left yet. The loose wool guys are coming in three weeks!

 

[Dr Benz]

I have some shims of various materials underneath where needed. String is a good idea. Hadn't even thought of it. Will check tomorrow, the train hasn't left yet. The loose fill insulation guys are coming in three weeks!

That sounds good. The plaster doesn't do well with too large deviations. I know….

 

[Rumpnissen]

No, if the surface is that uneven you'll either have to redo it or use a panel roof, it's more forgiving.

Why OSB on the ceiling?

Humm, okay. Bad news, but I understand. I'll see what I can do about the mess. Such a blunder...

The support beams are low, only around 80cm, so there will be a lot of ceiling. Who knows what you might want to attach there in the future. I also got a good price on 11mm OSB in 900 sheets, so I couldn't resist.

 

[Rumpnissen]

That sounds good. The cast doesn't do well with too large deviations. I know….

I know too 😬