Best way to handle roof wall plate over a wall offset?

[Digmixfill]

Hello everyone,

 

I've been dry fitting wall plates and have one niggle to deal with. It's an artefact of my wonky walls   When I built the new inner leaf it was stepped back from the existing walls to form the cavity. All of the other junctions are fine, but one junction across an internal wall has an offset of ~ 15mm. If I place the 75x100mm wall plate straight across here I get an overhang.

 

What is the best way to deal with this?

 

 

[Temp]

Silly question but why are you fitting wall plates?  Will ceiling joists be resting on them or new rafters notched onto them?

 

I think what you are doing might determine the best approach. If ceiling joist are going on top I would centre the wall plate on the wall. If rafters are being notched you really want them all to be identical so might be better for the outer edge of the wall plate to be in line.

[Digmixfill]

Re-roofing with new deeper rafters. They are going to be notched on to the wall plates.

[Oz07]

I've seen worse than 15mm overhang. If you want it looking neater put a half lap joint where that brick wall is and move the wall plate either side with a step there. The chippies might not thank you for it depending on how they measure and mark their rafters.

[Digmixfill]

I tried searching for details of allowable overhangs, offset joints etc, but didn't find any wall plate rules other than minimum 38mm deep, must be lap jointed and the 3m/3 rafter span minimum length. If overhangs and offset joints are acceptable I'll experiment and pick the option that is the least offensive

 

I'm going to be the chippie, I hope.  The new inner walls are equal heights, but with the building itself not being fully square they aren't parallel.  Only two birds mouth per rafter, but I won't be able to template and copy.

[Russell griffiths]

Don’t fix your plates down, leave them floating, as you cut your odd length rafters you can wiggle the plate in and out until acceptable, then after three or four rafters you will get a feel for the best location for the plate, fix it down and strap it then. 

[Digmixfill]

Bed and level the wall plates, but then knock them free of the mortar so that they are movable?

[Russell griffiths]

You won’t need to hit them much, soon as you nail the first rafter on they will come loose from the mortar. 

[Iceverge]

Centre each wall plate on the walls. 

 

Sit your ceiling joists on these. 

 

Sit a second plate on top of the ceiling joists. You can make it dead square to take any irregularity out of the roof. 

 

It also makes a very good junction thermally as you won't have to pinch the insulation at the wall roof junction.

 

 

 

This is a variation. You don't need the band joist and you will need to strap the top plate or the rafters to the wall. 

 

If you are tight for ridge height you can move the top plate further left to drop the rafters. 

 

Edited April 20 by Iceverge

[Digmixfill]

10 hours ago, Russell griffiths said:

You won’t need to hit them much, soon as you nail the first rafter on they will come loose from the mortar. 

That's good to hear.

 

5 hours ago, Iceverge said:

Sit your ceiling joists on these. 

 

It's room in roof. Wall plate, ridge beam and rafter is all I have to play with. 

 

I cocked up one calculation leaving an additional 25mm gap.    I'll have to grab a 100x100mm wall plate for that section.

[Iceverge]

I would consider splitting the wall plate into say a 100x50 and a 75 x 50.

 

You could put the 100x50 directly onto he wall following the bricks and making it level. 

 

Then put the 75*50 on top of it. You'd have 25mm wiggle room to ensure the whole lot was square. You could lap joints easily too for more strength.

 

 

[Digmixfill]

Does having a narrower top section to a wall plate, that might not be flush with the inner face of the lower section, affect the fixing of the restraint strap?