What's wrong with a SIP extension (self build)?

[Apache]

My project really has two halves - an old stone 'barn' that will be converted to living accommodation downstairs with 2 en suite baths upstairs. I have a SIP extension planned. That will have a large kitchen downstairs with a few small rooms at the back. Upstairs will be two good-sized bedrooms for my boys. 

 

Spoke with a few people, local builder, 'architect' although he does drawings and planning he's strictly not. All were favourable. The builders' son (also a builder) lives in a SIP house. 

 

The appeal for me - doing as much as I can self build. In a short period of time a structure appears that I then finish off. Cost seems favorable. It feels like a much 'easier' method of building, for me, than traditional block/stone. Even having a solid surface of roof to clad feels appealing.

 

@Nickfromwales seems to think I'm mad.

 

Born and bred in Yorkshire, have a thick skin. Tell me how it is. 

 

Thanks

[Nickfromwales]

19 minutes ago, Apache said:

@Nickfromwales "seems to think I'm mad........

.....to not explore all of my options before parting with my life savings".

 

End quote   

 

19 minutes ago, Apache said:

Born and bred in Yorkshire, have a thick skin. Tell me how it is. 

Game on

 

[saveasteading]

1 hour ago, Apache said:

doing as much as I can self build

That to me is decent justification. A kit reduces risk for the beginner, just don't try to change anything from a proven form.

It depends on more than that though. Geometry, the ground and topography, how it links to the existing...and more.

[Nickfromwales]

Have you not considered EPS ICF if it’s a bolt on to an existing stone structure? 

 

‘Speed’ with SIPs is one plus, but none of the other systems are slow . Basing your use of a particular system for that reason alone may not be the best approach to this, just saying .

 

As said, a SIPs style roof isn’t the quietest option, but it depends on what is important ti you I guess, and have you looked at the build up of layers that need to happen to complete the spec inside and out?

 

Typical SIPs will usually come as thinner sections than is ideal, or the cost rises for point of sale (making them look expensive at the point of an enquiry) and then you have to add more PIR internally to get the roof, and sometimes walls, up to a good standard. 
 

I have clients building with SIPs and they’re going through this annoyance presently, having to add 40mm of PIR internally over service battens, so are not just dealing with the time / materials / cost, but are also losing GIA due to the >65mm of encroachment into the interiors.

 

This can be added externally, but that still pushes the whole wall inwards however you cut it.

 

Consider twin wall timber frame too, as you can also stick build this with good chippy’s and even use I beams to create the structure. Then blow the whole thing full of cellulose so the sound deadening matches that of the original structure.

 

If you make the extension so it can be highly insulated and airtight, then it shouldn’t take much to get the rest of the original better performing, but it’s early days and I don’t know if you had planned to do any work in the existing parts or whether this is ‘just’ an extension and then you’re stopping at that?

 

More info and the plan for the long game would help us advise you best.

[Redbeard]

13 hours ago, Apache said:

In a short period of time a structure appears that I then finish off.

 

The same could apply with a double-skin timber frame with much more choice of insulant and a more 'permanent' 'feel' (both of those 2 words pretty vague in meaning in this context, but clear to my old brain).

[saveasteading]

My concern on SIPS is my own ignorance. That to a large extent is because they don't seem to aim at the professional contractor market... which to me suggests that it isn't commercially  competitive.

I see the systems used in Architect led projects where the end result seems very expensive to me... so I (cynically?) suspect that they do target the public at self build exhibitions, and some architects who are , unlike designer-contractors, not so aware of the real cost.

 

Hence quotes I have seen on here and elsewhere will exclude steels that may be needed, interfaces, perhaps even insulation targets.

 

 Thus beware.

 

3 hours ago, Nickfromwales said:

More info and the plan for the long game would help us advise you best.

absolutely.

To know how it works out in real life the pros on here need to know more.

The self builders who have used sips may well be very happy with the results, but have probably not got experience of other ways. But they will advise of what, if anything, to beware of.

 

My gut feeling suggestion is to you, as a self builder who wants lots of hands on and economy , is 'stick build'.  It fits, and is sympathetic to newbies*... it offers second chances. But you won't see that at exhibitions.

* that would include theoretical me if without builder help.  Strip footings, stud build, timber cladding, timber roof, metal sloping roofing, or tiles.