Oz07

Take external skin right way up level with top of rafters, pro need to leave top course till rafters on so know where to set line. Take internal skin up and either sit rafters ontop or use a pole plate and hangers. If sitting rafters on blockwork probably need trimming to sit flat on the block and a bent strap hanging over end of blocks. Can you do this off your own back nowadays or do bcos want some kind of detail drawing

What if the other 3 walls of the garage 4" brickwork

Yeh but if the other walls of the garage are 4" brickwork with pillars what would it be achieving. Logically it wouldn't have any benefit?

So with a single storey garage adjoining a 2 storey house would you bother with the stepped tray or not. It's going to disrupt the continuity of insulation, im not even sure if blown insulation would overcome this. The garage wouldn't be integrated so would have good ventilation. I wonder if bco would make you put the tray in or in this case let you omit.

Have your building control or local council given you the address?

Low exposure area, midlands. I would say high exposure relative to the location. Opposite a park at the top of a small hill, no soffit overhang. Rain quantity high we had emergencies declared early in the year lots of local floods. Stretcher bond so average amount of joints. Height of wall only 2.5m. Has anyone ever actually seen water running down the inside face of a 4" wall? It probably does happen in more exposed areas but I've never seen it. I've always used trays in the past just thinking out loud.

Crazy I'd never of thought so. I had a garage with a section of 4" wall and piers. Part of it faced south and was quite exposed. Never once had water streaming inside although the wall did look a bit damp after a prolonged period of wet weather. How do we explain that?

Found this on YouTube demonstrating the problem i suppose blown insulation avoids the problem IF it gets in around the trays ok. Probably best to avoid this type of abutment if the insulation can't be don't well and water really does stream down inside of cavity.

I just can't envisage that much water getting in. How many weep vents do you ever see dripping water. How do you know its running down the wall inside?

Is there really a need for cavity trays? When talking cavities 150 or 200mm how likely is it that moisture bridges the cavity. I'm thinking about stepped cavity trays where single storey garage abuts a house. Such a pain to do and if using cavity batts the insulation is never going to be as good around the tray detail. How likely is it any significant amount of water is making its way past the brickwork let alone getting to the inner skin.

Like I say I just used 100mm dpc. Bottom, up sides and onto stooling. Jointed in middle with standard mortar touch weaker if anything. No probs.

Did you literally have the firm commission your mhvr or did you buy any other products or services through them? I struggled to get a decent contractor to commission even after having used a reference from supplier. Maybe an easy fix to the door is a hidden key safe somewhere. We've had one on last 2 houses its good for cleaner and unexpected visitors.

I always thought the only reason for the dpc was so the brick and stone could move differently without cracking the stone. Wet cast stone doesn't need apparently much stronger the dry cast is weaker. You only have to look at them funny and they chip

I don't think moisture from weather during building brings mould later. Isn't mould more to do with humidity and ventilation once finished.

Nothing disastrous to me there. At least your floor deck isn't on. The insulation would surely dry out in time? Stopping the insulation at that dpc level is poor but nothing to do with being exposed to elements. Ideally you want it to overlap the level of pir insulation in floor so say going 225mm below dpc. Id consider having this area of missing insulation blown in with a machine as I think it would effect your real life performance. Any reason for traditional timber joists? It looks a smart job just not common on new build. Was there a big saving vs posi or I joists?