Just discovered purlin barely supported on a corner of a brick -HELP

[datarebal]

Jacking might lift the lower part of the roof off the wall plate.

Correct

 

[noseall]

If it's been like that a while, the rafters may have undergone a permanent set (known as 'creep', which timber is prone to long-term).

Agree - hence my 'memory' remark in my first post.

Once the tiles are off, it might be easier to sister the existing rafters with new 75 x 50 set to give an even slope.

The problem is that the existing rafters are bowing downwards. If a new purlin is fitted, either along side or as a replacement, then the existing rafters will either have to be straightened or replaced. Your suggestion would only work if no purlin were involved.

@ the O.P. - I would also get the chippy to fit a thickening piece to the hip blade, at the point where the two purlins meet, so as to collect the whole depth of the purlins. I'd also strap/fix the purlins together once this is done.​

 

[tony1851]

If a new purlin is fitted, either along side or as a replacement, then the existing rafters will either have to be straightened or replaced. Your suggestion would only work if no purlin were involved.

I'm not sure existing rafters would need replacing, particularly if the purlin was just extended by bolting a piece on; the modified purlin doesn't have to be perfectly horizontal.

 

[noseall]

the modified purlin doesn't have to be perfectly horizontal.

Eh?

 

[tony1851]

Eh?

The. Modified. Purlin. Doesn't. Have. To. Be. Perfectly. Horizontal.

 

[noseall]

The. Modified. Purlin. Doesn't. Have. To. Be. Perfectly. Horizontal.

Are you suggesting replacing a faulty purlin with a bent one to deal with the curved rafters? How will that go with the new straight sistered rafters you suggested? They wont meet the curved purlin. Or are you suggesting the new ones should be bent as well?

You don't have to be a patronising coont.

 

[tony1851]

Are you suggesting replacing a faulty purlin with a bent one to deal with the curved rafters? How will that go with the new straight sistered rafters you suggested? They wont meet the curved purlin. Or are you suggesting the new ones should be bent as well?

No. What I'd suggest is;
1. temporarily prop the purlin near the end;
2. cut back the end of the purlin sufficiently to chop away the projecting brick and bolt a short piece of timber to the brickwork to form a better ledge for the purlin.
3. extend the purlin on to the ledge by bolting a short length (4ft?) of 9x3 on to the end, and bridging on to the timber ledge - this means the purlin stays in its present position, but is better supported.
4. (assuming tiles are being removed) sister the rafters with 3x2; - where they sit above the level of the purlin where the roof dips, just pack between each sistering piece and the purlin with timber offcuts to make sure the load is carried on the purlin.

 

[noseall]

No. What I'd suggest is;
1. temporarily prop the purlin near the end;
2. cut back the end of the purlin sufficiently to chop away the projecting brick and bolt a short piece of timber to the brickwork to form a better ledge for the purlin.
3. extend the purlin on to the ledge by bolting a short length (4ft?) of 9x3 on to the end, and bridging on to the timber ledge - this means the purlin stays in its present position, but is better supported.
4. (assuming tiles are being removed) sister the rafters with 3x2; - where they sit above the level of the purlin where the roof dips, just pack between each sistering piece and the purlin with timber offcuts to make sure the load is carried on the purlin.

Alternatively, have a brand new straight purlin with straight rafters. Seems like you are forgetting your oath.

 

[catlad]

Usually once the load is off the roof you can straighten the roof without the need for more timber. But it is sometimes nescessary to sister to the old to new to get the roof back level.

 

[noseall]

chop away the projecting brick

Have you given thought to the other end of the brick doing a mirror image of what we see, on the neighbours side? Bonkers - yes, but so is resting a purlin on a corbeled brick.
I'm concerned that this may be the scenario....

Partyw

• noseall
• 2 May 2020

 

[noseall]

Usually once the load is off the roof you can straighten the roof without the need for more timber.

Only if the rafters behave themselves. They (the rafters) may want to stay in the shape they are in. A new purlin will want to go in a straight line from the hip blade to the party wall. Any dipping rafters will interfere with this.

 

[catlad]

Once the roof is undone the normal 3x2 rafters can be straightened and re-fixed as long as they are not like a bow.
If the purlin has lost its shape then the rafters can be packed with lead strips were it lands on the purlin using a string line as a guide and then re-fixed.

 

[noseall]

If the purlin has lost its shape

That's the thing - I don't think the purlin has. And I would want that purlin up where he belongs, i.e. up tight against the rafters and in his original position.

This possible scenario bothers me more regards remedial work and the party wall..

Partyw

• noseall
• 2 May 2020

 

[catlad]

Yes I understand, not going to know unless you are onsite.

 

[stolonsi]

That's the thing - I don't think the purlin has. And I would want that purlin up where he belongs, i.e. up tight against the rafters and in his original position.

This possible scenario bothers me more regards remedial work and the party wall..

Partyw

• noseall
• 2 May 2020

What would be the concern for the scenario in your diagram? Would it be better to rest the purlin on a metal bracket or plate which is bolted to the brickwork?