Anyone ever used SIP panels?

[GMM]

Just pondering my extension project. Basically a lean-to design (6m x

4m approx) and 3 walls are already there so I need to renew the floor, build one long wall and add a roof. I was planning a conventional cavity wall but got to wondering whether SIP panels might be viable. Broadly speaking, they seem to be about similar overall on cost, replacing the inner skin of blocks and the insulation but should go up much quicker.

Is that really true though, or are there unseen buggerations in using them? Any experience would be good to hear.

Cheers

[Tim Lamb]

In message , GMM writes

No experience but some thoughts..

If you are building a blockwork outer skin, why do you need a structural inner?

Clearly the OSB inner skin will provide better fixings for wall hung kit than the plaster board faced PIR from Kingspan etc.

Nice not to need a 4" cavity but what about lateral water penetration? Will you need weatherproof cladding on the outer blocks?

[meow2222]

Quick to build, quick to rot

[dennis]

On most modern houses its the inner that holds up the floors and roof. Even with modern timber framed houses the inner is the structural part.

[The Natural Philosopher]

Having thought about this, I think you are in fact correct.

Conceptually, a modern house is a structurally integral inner, then insulation, and then a weatherproof covering.

And as little possible connection between inner and outer shells to avoid cold bridging.

If you make the outside structural, then you have to build a living space inside that, and that living space still needs to support the weight if itself - if not the roof.

And transferring loads to the outer walls means structural ties.

One can imagine a house built like an igloo, with lots of structural strength, inside which is suspended an insulated cocoon in which people live :-)

only cold bridging is by some steel cables..

[Hugo Nebula]

'Cos a 100mm brickwork wall isn't enough by itself to prevent lateral movement. It has to be either a) thick enough to support itself (i.e.,

9" thick), b) tied to another leaf of masonry, or c) tied to another structural frame.

Strictly speaking, with c), it's the frame supporting the building, and the masonry is acting as a weather resistant cladding.

OP: I'm sure you CAN use SIPanels for one wall of an extension, but what about design & lead time? I've only seen them used on large buildings or housing estates. Blocks have the advantage that they're quickly and readily available, and they can be cut to size. For one wall, I suspect it would be quicker for one brickie to build inner & outer leaves, than for your panel to be craned into position, a chippie to fit it, and then a brickie to build the outer leaf to it.

[The Other Mike]

Try uk.rec.models.engineering. One of the posters there buit a workshop the size of his garden with SIP's. It was fully documented online with loads of photos.

4th post down here has one photo

[The Other Mike]

Found the website

Week 66 onwards or thereabouts

[Tim Lamb]

In message , Hugo Nebula writes

Lots of garages still standing: with piers at 3m :-)

The OP was planning a lean-to so presumably single storey.

An architect came up with a single storey pitched roof extension for me which got past our local building control and was intended to have pb faced PIR dot and dabbed interior. In the event, the builder used cavity blockwork so we have a very narrow shower room!

[Hugo Nebula]

It's all about balancing risk, cost, etc. The risk to life is lesser in a garage than an extension, so the risk of a wall cracking or collapsing can be greater, hence it is allowed in small single storey non-residential buildings and 'annexes' (e.g., a garage).

As you point out, a half-brick thick wall has to have pillars at 3.0m maximum centres. If this was incorporated into an extension, there would look odd to have these thickenings at doors, windows and in the middle of a wall.

[Man at B&Q]

There was a Grand Design with daughter building with SIPs from Daddy's company (I think, or maybe he just put up the money). Should be available on 4OD but no idea when it was first broadcast (a few years ago).

MBQ

[GMM]

Well, the inner skin of a blockwork wall adds to its structural strength. I'm not (yet) convinced about the ability of two sheets of PSB on end to support the roof, but maybe that's just me. There's normally a membrane over the SIPs, then a cavity, then a brick outer skin.

[GMM]

Well, they come in 8x4 panels, all ready to fit together, so I would have thought it would be pretty quick to put them up and one panel shouldn't be any more than two people can handle between them (assuming I can ever get the lad out of bed this summer)

[GMM]

Well, that's no recommendation in terms of speed by the look of things - it was the work of years (literally). I assume that was more because it was an ooccasional weekend sort of job rather than a concerte effort though.

I wonder what the neighbours made of his little shed?

Elfin safety would have a field day with some of those photos!

[Andy Burns]

I was thinking "neighbour dispute", but still seems to be standing

[dennis]

The SIP also stops the brickwork skin falling over not just supporting the roof.

A "conventional" timber framed house supports the roof on a few 4x2 vertical timbers and a single skin that's there to stop the frame folding up.