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Kingspan.. for a dummy.


zoothorn

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I'm just about to jump in & fit 140mm kingspan into my new timber frame walls. My bco has specified full 140mm (sigh). I've fitted 25mm celotex before in 2x kitchen walls, easily cut with a sharpie.. but this is behemoth thick in comparison so I'm a bit daunted by the prospect of the job.

 

Are there any tips? or is it only a case of measure, saw, stuff it in? I have approx (25x) 2300m H x 500mm W sections/ gaps between my 140mm timber verticals to do. Electric wiring all done, & generally pushed/ clipped at the back or in corners: navigating around cables I could do with a few tips on.

 

Any help much appreciated- zoot.

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Your going to find it a challenge to keep a straight cut with the 140mm.... it gets easier after you get into the swing of things. If I have to do any angled cuts I run the big circular saw through it first as it leaves a perfect angled cut, I them follow the cut through with the hand saw. If your struggling just do the initial cuts with the circular saw and go the rest of the depth with hand saw. Wear overalls, hat, mask and goggles if working overhead, strip of every time you go back into the main house as the dust is unforgiving on your lungs. Remember to take the mask of last. It’s a pitiful job. Decide early on if you going for tight fit or foam fit and cut accordingly. If foam fitting I always jam the insulation boards in place with either plastic window spacers or pre made wooden wedges before foaming it in, the jamming will prevent the sheet from moving and help maintain an even gap round the board. Personally I think your best going for a tight fit as foaming 140mm boards with any accuracy is very hard and will use a lot of foam, but it’s all down to how good you can cut the boards.   

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Use two layers (unless you’ve bought it already) and it’s easier to fit around wiring etc. 70mm is standard thickness board - Seconds & Co isn’t that far from you and they deliver and will be cheaper than the merchants. 

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1 minute ago, scottishjohn said:

hot knife?

or a pupose made foam cutter blade for a reciprocating saw

 

I did try making one with kanthal/nichrome wire. Certainly had merit but a bit smelly. I kept breaking the wire though. No dust is a bonus.

 

Table saw with a really good dust extraction system is imo by far the best and most accurate.

 

The slightest gaps defeat the object. Some advocate cutting 5mm or so shy of the gap if doing by hand and foam filling. 

 

I think we mulled on here making a bfo manual / push one based on a giant, super sharp/ thin pizza cutter type wheel.

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4 minutes ago, Onoff said:

 

I did try making one with kanthal/nichrome wire. Certainly had merit but a bit smelly. I kept breaking the wire though. No dust is a bonus.

 

Table saw with a really good dust extraction system is imo by far the best and most accurate.

 

The slightest gaps defeat the object. Some advocate cutting 5mm or so shy of the gap if doing by hand and foam filling. 

 

I think we mulled on here making a bfo manual / push one based on a giant, super sharp/ thin pizza cutter type wheel.

 

Thanks alot chaps. The Onoff YouTube clip is ideal info (Id never have found such a good eg/ chap seems a boss), using the timber for a straight edge, marking with the tape (ace tip), friction fit I'm going for & if needed fill any gaps after with sudal LE foam.. & I too have a magic pink saw. I just can't face attacking with a circ saw/ dust & noise too much.. & I dont have a tablesaw. Handsaw it is.

 

Ok that's a basic plan of attack. Ideally as PeterW says 2x 70mm would have been wiser now, but £more (& PIR bought before xmas before £hike in january.. saved £80 alone).

 

Great help- zoot.

 

I'll keep reading the replies before I wade in though.

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8 minutes ago, MJNewton said:

A bread knife can also be handy to trim thin slithers off if/as required without virtually any dust. 

 

 

That's a good tip MJN.. got the ideal one for job (I use it for bread, & for cutting turf last spring too!) so its now a multi-tool-bread-knife then.

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10 minutes ago, scottishjohn said:

Iwould make an extrra large base plate for jigsaw --so it keeps it sat right angle to foam -bit of ply fixed to std jigsaw base.

 

Jigsaw is an interesting idea.. I was just mulling on that (going along a straight edge-?). The depth would only get me halfway is the only thing.

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45 minutes ago, PeterW said:

Hot wire won’t cut PIR as it won’t go through the foil. Bit of straight timber as a straight edge - floorboard or an offcut of a chipboard floor panel - and a new handsaw. 
 

 

My hot wire cutter did cut the foil on Celotex...but not for very long...

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