Feedback on timber extension structure

[JackOfNoTrades]

13 hours ago, Redbeard said:

I take your point, but if you look at it in the context of a whole-house plan enacted over a very long period (possibly finished by the person(s) after you), there's still logic in getting the best you can from each element that you do 'enact'. 

Fair point. I am now considering including 150mm insulation (costs and extra £130 for this build to beef it up) particularly because I need to lay some telescopic vents in that space to ventilate the suspended timber floor in that part of the old house. 

 

 

2 hours ago, stu w said:

Looking at you drawings you are doing 600 centres ? If so BC may require noggins on load bearing walls also doubles at the existing walls.

 

Doing 400 centres on this one. To be honest, I do prefer including noggins, even though I know at 400 the OSB should do the job, but it just doesn't feel right. I did noggins on my last build but here I am trying to reduce the amount of timber bridging because of the required size of jack studs elsewhere. 

 

 

2 hours ago, stu w said:

Hardie Plank rather than VL ? 

I'm using VL on the boundary facing side (no access so once that wall's up I want it to be up and maintenance free until after I'm dead. A slither of it will be visible by the neighbour so I'll want it to look nice for them too). But then I'm using open slat Siberian Larch cladding on the rest of the build. I just like wood. 

 

2 hours ago, stu w said:

Are you going to fix through your dpc for sole plate fixings , or try and fix it down externally/internally ? 

Still working on this. The TRADA publication on it says that shot fired is most common method with masonry nails going at least 25mm into the blockwork - not comfortable with shooting nails into blockwork - and regardless I have the thermoblock in the way. Other options: 
Straps - pros: not going anywhere on a windy day. No penetration of DPC. Can extend below the thermoblock easily. Cons: at risk of corrosion externally? 
U-shape or L-shape anchor - Pros: can bolt deep down through marmox and into the blockwork. No penetration DPC.  Cons: Would need long expanding bolts to get it through marmox and into the blockwork. The thickness of the anchor on top of thermoblock stops the surface from being 100% level for the sole plate. [EDIT - but could obviously use mortar to level it]
Just bolt it through - Pros: simple, all self contained within wall. Cons: Need to squirt something down to seal the DPC. Bolts need to be long. 

Think I'm leaning towards anchors at the moment. 

Thanks for all your thoughts and comments. I really appreciate it loads.

Edited April 12 by JackOfNoTrades

[JackOfNoTrades]

1 hour ago, Russell griffiths said:

With your gable ladder type arrangement 

would you not be better taking the smaller, flying rafters internally an extra rafter gap, so you get a counterbalance effect on them. 
depends if you need extra support if your soffit is large. 

Good point. And actually I don't really need that extra joist by the side of the wall, so I can extend the flying rafters to the next joist. It's only a 68mm extra overhand on that side, but it also removes the (unnecessary) weight of the extra joist on that wall. 

 

Edited April 12 by JackOfNoTrades

[stu w]

2 hours ago, JackOfNoTrades said:

Fair point. I am now considering including 150mm insulation (costs and extra £130 for this build to beef it up) particularly because I need to lay some telescopic vents in that space to ventilate the suspended timber floor in that part of the old house. 

 

 

Doing 400 centres on this one. To be honest, I do prefer including noggins, even though I know at 400 the OSB should do the job, but it just doesn't feel right. I did noggins on my last build but here I am trying to reduce the amount of timber bridging because of the required size of jack studs elsewhere. 

 

 

I'm using VL on the boundary facing side (no access so once that wall's up I want it to be up and maintenance free until after I'm dead. A slither of it will be visible by the neighbour so I'll want it to look nice for them too). But then I'm using open slat Siberian Larch cladding on the rest of the build. I just like wood. 

 

Still working on this. The TRADA publication on it says that shot fired is most common method with masonry nails going at least 25mm into the blockwork - not comfortable with shooting nails into blockwork - and regardless I have the thermoblock in the way. Other options: 
Straps - pros: not going anywhere on a windy day. No penetration of DPC. Can extend below the thermoblock easily. Cons: at risk of corrosion externally? 
U-shape or L-shape anchor - Pros: can bolt deep down through marmox and into the blockwork. No penetration DPC.  Cons: Would need long expanding bolts to get it through marmox and into the blockwork. The thickness of the anchor on top of thermoblock stops the surface from being 100% level for the sole plate. [EDIT - but could obviously use mortar to level it]
Just bolt it through - Pros: simple, all self contained within wall. Cons: Need to squirt something down to seal the DPC. Bolts need to be long. 

Think I'm leaning towards anchors at the moment. 

Thanks for all your thoughts and comments. I really appreciate it loads.

Had mine delivered this morning 💴💴.

Wouldn't be any issue with corrosion with stainless steel straps and fixings