Going on from http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=7573&page=3#Item_3

Take a look at this http://www.parex.co.uk/Render_video (you may have to register with the Parex site) - trimming by crumble/hacking as a handsaw does, and frightening slappy gappy installation, in Parex's own 'best practice' (?) video. They think this is OK, incl no special care to keep cement (as alternative to fresh air) out of the joints.

I've just been taking to EWI installers, who say they hate to have the insul installed by the GC, for them to finish - they want to do the whole themselves. Well, if this is how the specialists do it, as approved and trained by the manufacturers, I'd sooner have an untrained but 'caring' chippy, cutting by hot wire and polyurethane foam adhesive gluing the joints as they go, or afterwards with long-nozzle squirty-foam. Why don't the manufacturers make the joints part of their system?

Tom, the solution to the ragged sawn edge is the appropriate insulation saw, mentioned on the forum previously, but whether most installers know of their existence I doubt, its usually whatever falls to hand. (or as you say the hot wire method but is this limited in thickness of insulation). The existence of gaps, be they full of air or mortar, is unforgivable and just poor site practice and should, in my view, be totally unacceptable, but then I'm a fussy so and so.

an02ew, interesting to see you can cut up to 225mm in thickness with the hot wire method. Have you had any experience of using a insulation specific saw on EPS ?

Hi Mike, thanks for this, I am hoping to apply a 300mm thickness of EPS to the outer walls (probably in 2 layers of 150mm, staggered joints) so it would appear the saw approach is not the way to go. Home made water jet anyone !

Brilliant pics Andy - and nice to see yr house coming on. How portable is that table, when not working at home?

Hopefully you wouldn't have to foam gaps afterwards if you'd cut neatly and bubble-glued as-you-go. The two are either-or's.

Posted By: spoonandforkif the sheets are tightly fitted, but cut with saws, do you think those gaps are significant? I can't imagine the air is moving around much in such a small space...

It certainly does and seriously degrades actual insulation performance - the prime reason why buildings traditionally have performed way below design assumption, and heating engineers have found the need to double calcd boiler size 'for luck'. It's serious. And still inherent in all cut-board and roll insulation methods, without scrupulous precautions that cancel their supposed low cost.

Posted By: Cav8andrewHave you had any experience of using a insulation specific saw on EPS ?

Yes, they are good and can be sharpened with an ordinary file. We use this for the man on the scaffold who can make minor adjustments when fitting. Also i have used an insulation blade for the alligator saw great for PUR although a bit fast and uncontrollable for EPS

Posted By: Mike GeorgeThe main advantage of the saws are the clean cut and minimisation of dust

I disagree the hot wire cutter has NO dust.

Posted By: fostertomHow portable is that table, when not working at home?

The table is made of some site 4x2 and 1 plywood; say £40, just but it new for each job. Then put your battery charger and re-enforcing metal T piece in the van, roll of wire in the pocket. How much more portable could it be?

Posted By: an02ew

Posted By: Mike GeorgeThe main advantage of the saws are the clean cut and minimisation of dust

I disagree the hot wire cutter has NO dust.

Ah, sorry, I wasn't clear. I meant an advantage over other saws, not a hot wire cutter

Posted By: Cav8andrewlove the idea of an alligator saw for cutting EPS, in my minds eye I see a veritable snow storm

The blade for the alligator saw is just a thin shape blade that heats up when used, there is little dust.

Posted By: Cav8andrewit looks as if a homemade hot wire cutter is in the offing if I want to cut 150mm.

Good idea if you have any quantiy to cut or shape.costs around £80-£90

I'm looking at EWI videos, to get a spread of what the manufs regard as best practice. The Parex one that started this thread portrayed appalling practice - but there's nothing wrong with Parex if intelligently applied. Same is prob true of all systems; but some manufs are more together than others, in the standards and practices that they themselves specify.

Here is a very informative video from Wetherby http://www.youtube.com/watch?feature=player_embedded&v=x0L5YjQ50Pc incl render, dash and brick slip work. It shows a thin (50mm?) insulation board so gives few clues about using the thick boards that we discuss here.

As seems universal, the board edge-joints get no attention - just 'must be tight butted'. Well, even with thin boards the joints look gappy in this video. AFAIK any gap even fag paper thickness is a bypass heat-leak route, with quite strong convection forces causing constant (if slow) circulation of air from wall to surface and back. Let alone 1.5-2mm as it seems here, or 5mm which may well be with unflat walls and/or thick boards (supplied with inaccurately-square edges).

Been talking with applicators, who are trained by the likes of 'pukka' Sto in this case, to think they have all the answers. On one hand they insist on a base rail, which is very expensive, to establish a straight flat starting line, and as DPC. On the other they won't hear that joints are a heat-leak. They must use XPS below DPC, and certainly below ground. All of these, my experience so far would dispute. As a result they cost 70% more than other applicators. They won't consider finishing on boards accurately cut, edge-jointed and fitted by chippys.

i'm trying to get a handle on what's important, and what is unnecessary elaboration, even counter-productive. Are we mesmerised by 'specialist' expertise when in fact EWI should just be normal builder's work?

And now I've just talked to a well recommended applicator who is very happy, in fact prefers, to just do the rendering, on board fixed by e.g. chippys, saying that most of the applicators' board fixing is rubbish, and there's a whole old mystique about it.

When you think about it, plasterers, masons, groundworkers just in the end apply gungy stuff and spread it out. They don't think precision, engineering-style. Chippys do. So when it comes to accurate board cutting and fitting, it's chippys work. After all, it's accepted that chippys fix plasterboard, not the plasterers. And there's always the danger that you'll get 'insulation fitters' who with all due respect are near lowest in the building industry.

It’s a very well made and convincing point Tom, had a meeting with Parex man today, he’s very impressed with our EPS installation (as chippys) he also mention that he has never seen anyone take the time to gap fill all joint with foam fix, and was also well impressed with the hot wire cutter and spray glue even took information on glue, he has no problem at all we me fitting and fixing all the insulation and echoed your points exactly. Also mention a spray applicator for the Parex top coat (DPR) that can spray up to 3mm grit for better finish and far better coverage per tub?

All i need now is a trowel for the mesh coat and I’m away, just got room for another line on the van“EWI SPECIALIST" should fit nicely between "ground works" and "Brain surgery"

Posted By: fostertomAnd now I've just talked to a well recommended applicator who is very happy, in fact prefers, to just do the rendering, on board fixed by e.g. chippys, saying that most of the applicators' board fixing is rubbish, and there's a whole old mystique about it.

When you think about it, plasterers, masons, groundworkers just in the end apply gungy stuff and spread it out. They don't think precision, engineering-style. Chippys do. So when it comes to accurate board cutting and fitting, it's chippys work. After all, it's accepted that chippys fix plasterboard, not the plasterers. And there's always the danger that you'll get 'insulation fitters' who with all due respect are near lowest in the building industry.

Ah but theres plasterers and then theres PROPER plasterers

But many a plasterer is longing to be allowed to do Brighton moulded work, East Anglian plaistering, simulated brickwork - very skilled, many of them. They must be bored stiff with flat work on a tight price.