New Porch Questions

[Micky Dripping]

Hi all,

I've started building my new porch and have a few questions before going any further. I have the foundations poured and block work up to DPC, but I am wondering about the best way forward for a couple of areas.

1. How do I install a vertical DPC if the outside door is only fixed to the external skin and there isn't an internal skin to tie to? If I cut a cavity break, the door will not be fixed to anything other than a thin column of Reformite blocks and would most likely fall out.
2. I am also at the point of installing insulation as I start upwards and this also seemingly has various options. Full fill 75mm cavity? The remainder of the house/bungalow has a 50mm cavity, now cleared awaiting refill, but I could also get beads blown in at the same time as the rest of the house, or is it better to build in slabs? Blown insulation would be full fill, so I suppose that's one question kind of answered.
3. Wall ties. Which course should they start at and regarding spacings, how many, as there is not going to be much room for more than a few. One returning wall will have a small window and the door will be in the front, so only one wall without openings and it's 1.5m wide approx.

I have a whole bunch of questions to ask, as it seems as although this is a small porch, it really isn't too different from a full on extension, except in size and although there is a lot of information and advice, quite a lot of it seems contradictory or perhaps just outdated.

 

[^woody^]

Ideally the new inner skin would be bonded into the house and this would mean the door frame is fixed to that. But that would be a loft of work and mess. So, you need to chop the render off and fit a steel wall starter tie and the external render should prevent damp from moving sideways into the new porch. There will be a cold bridge so you should line the bit of the old reveal with some thin insulation.

Use Dritherm or Rockwool full fill cavity batts

Ties go on the DPC course, below the DPC material

 

[Micky Dripping]

Thanks for the response, totally agree that ideally, toothing in would be the way forward, but given the construction I'm dealing with, not really possible.
I might try to find some offcuts of phenolic boards, they are supposedly very good, if expensive.
The render that is currently shown, was put on to try to level the wall a bit, as it's made of various sized split faced concrete blocks, 60's style and there isn't anything flat to fix to.
It's not going to be perfect without totally removing the part of the wall that the door fits into and rebuilding, but that isn't practical, so it's a case of making the best of a bad job, unfortunately.

 

[cdbe]

You have my sympathy, bit of a headscratcher- I just went for continuing the cavity round the corner but it's a messy job -you'd have to build that doorframe back in. If I recall correctly, ties are 600mm horizontally at DPC then 900mm horizontally and 450mm vertically and 225mm vertically around any openings, no more that 150mm in.

My dad's single skin porch has been butted up to the outer skin of the house since 1985 (connected by crocodiles - as they were known as back then) with no issues - although on paper I think I should expect some damp penetration it hasn't happened. Might be worth running whatever you do past your BCO.

 

[Micky Dripping]

Thanks again. I'm going to have to do whatever seems like best practice for each stage.

As it's a 60's bungalow (and not especially well built either) with untold bodges over the years, it's not exactly compliant with many (any current) regs, so the porch being as per current standards isn't going to matter really, as long as it is structurally sound and as warm and dry as I can practically make it.

I'll update this post as the project develops, which will be whenever I can grab some time to progress it.