epsilonGreedy

I will explain in simple terms. Having owned sailing yachts for most of my adult life I have picked up a lot if insight into grp hulls and their manufacture. I have never heard of moisture being a problem in a hull manufacturing plant. The patchy quality control, largely of British built yachts of the 1970 and early eighties has triggered much interest over decades as to what can go wrong when a grp hull is made. @JSHarrisas claimed moisture it is a major recognized industry problem that even the lowly laminators on the production line will consider moisture the main enemy of good grp. It is odd that such a concern has never entered the consciousness of two generations of yacht owners given that osmotic blisters, the most common failure, lead to a £9k bill to fix. Given that an exothermic curing laminate will drive off moisture I find Jeremy's claim very odd. I was once very interest in a fringe yacht design where the hulls were grp encapsulated plywood. After a decade or so it was recognized that once water got inside to the wood, the grp sheathing would progressively fracture as the wood swelled, this was a runaway process. I believe this is the root cause of the OP's roof failure and a more likely explanation than edge case science about moisture captured in grp during layup. It is a bit like saying if a shovel full of topsoil is thrown in a cement mixer to bulk up the load the house might fall down, well yes of-course but it is more constructive to discuss the probable than the unlikely.

British yacht construction suffered much worse than comparable manufactures on the continent. The mainstream UK yacht manufacturers Westerly and Nicholson (think Austen/Morris and Jaguar) had a terrible osmosis record, it became an industry joke and their business failed. There is no volume mid market British manufacturer of sailing yachts left My new yacht was manufactured in Germany by a company that is still the No.2 volume producer today. Defo no chopped strand there, infact the whole chopped strand debate is a bit of vintage discussion, I think a few budget brand powerboat companies in the US were the last to abandon that years ago.

100% wrong. I once owned a new yacht with a curious crack in the deck, after much head scratching the problem was opened up with an angle grinder at which point the experts went ah ha, the laminate had cooked on the moulding joint where resin was laid on thicker. I was then advised there is a constant juggling act in hull lamination between production targets that favours more layers of laminate per cure compared to quality control who want to avoid cooked laminate.

Let's summarize, you solved a £ billion manufacturing problem 30 years ago and the secret is still for sale. Hmm.

@JSHarris comprehended my point.

The boating world now uses vinylester or epoxy resins to solve the osmosis problem. The apparent randomness of the occurrence of osmosis in boat hulls perplexed the industry for decades, how did you solve the osmotic mystery all those years ago?

The curing of a resin is an exothermic process, laminators spend more time worrying about an excess of heat cooking the uncured laminate.

A boat can suffer grp osmosis even when hauled out for 4 months of the year but yes must less of a problem on a roof which is why I doubted your theory. Since the vast majority of grp fabrication takes place in a factory environment I doubt 1 in 10 grp laminators thinks about moisture at all. The vast majority of discussions on grp & moisture relate to osmotic degradation.

The problem you refer to is osmosis in polyester resins and takes 10+ year to appear. It occurs even when the original grp layup was done correctly in dry conditions. I suspect the OP suffered a mechanical failure and not a chemical one.

I reckon the original roof failed due to swelling of the OSB3 and present leaks suggest this process continues. If the current roof is prone to leaks why is the builder confident it won't release its existing captured moisture upwards into the new OSB overlay?

Below ground footing blockwork often looks messy and need not imply the same team will do the same higher up the elevations, though it does appear worse than mine. The mortar mix looks strong which is correct below dpc. I would be more interested in levels and how square the plan view is.

Room size and property style will also influence minimum ceiling height. When aiming to reproduce a heritage cottage style property 2.2m might be ok. A low ceiling in a large room will also be more noticeable. The default minimum is 2.4m on the ground floor for anything but budget low-cost homes and 2.3m or 2.2m upstairs. +2.6m starts to give a property an air of grandness. Given a ridge height limit you can steal some extra ceiling height by specifying roof trusses with a raised horizontal joist which introduces a foot or so of sloping ceiling in the bedrooms.

An interesting association which indicates how much we have yet to learn about climate change. Re. the weakening magnetic field, I am more concerned about damaging solar rays bringing down the worlds communication networks.

I spend a lot of time reading about the lack of climate change but did not respond earlier because I suspect contrarian material that doubts thermogeddonist culture would not be welcome. The actual present convulsions of the earth's weakening magnetic field and after that the issue of plastic choking the worlds oceans are issues I spend more time worrying about.

I thought gypsum was an old fashion term for a special manufactured cement sandwiched between cardboard sheets to create a composite, but I think you are saying it is different chemical compound to OPC. Anyhow my curiosity is satisfied, previously I had assumed the special disposal regs were something to do with the dangers of inhalation.

This seems like the right thread to ask a question which has bugged me for a few years. Why is plasterboard considered to be such a toxic material in skips or recycling centers? I would rank old liquid paints much higher.

Indeed and as photos posted here previously demonstrate, voids in fitted of cavity batts occur. Thinking about this some more I reckon the risk of voids in blown beads reduces in cavities wider than 100mm. How much faster would a brickie team work if not fitting insulation cavity batts as they go?

I am still tempted to go for blown beads but do not think a new build within 20 miles in mid Lincolnshire has been built with these. The standard response from builders (pro and amateur) is a confused face followed by "isn't that what they pump into older cavity walls"? A visiting EPC assessor commented, "you will get voids". Must been a regional thing.

In case anyone else is also wondering what a check reveal is. https://www.illbruck.com/en_GB/solutions/window-installation/check-reveal/

Call me a cynic but I interpret that as "once they have secured a mortgage for you they will then attempt to cross-sell other related financial products".

Fab detail there Ed. Since I am starting from scratch and want a low EMF house (i.e. as little WiFi as possible) are there wired alternatives for these sensors? My current plan is to wire the my house with an excess of POE capable Cat-6 cable in the hope this will accommodate future plans and technology trends.

No but now I am thinking... should I be considering mobility door threshold levels already? Flooring will either be some high-end ceramic tile that mimics a French limestone floor or something more sophisticated. I recall offending a retailer at a selfbuild show, "no sir we don't sell ceramic tiles, these are reconstituted stone floor tiles".

Non technical factors are encouraging me towards flow screed and from my reading on the subject 50 to 60mm is the norm for flow screed, hence I am looking for an unusual insulation depth of 160mm. 75mm of traditional screed feels like a better choice which I assume has a greater heat capacity hence it could soak up more KwH of cheap rate overnight electricity. Also putting aside flex strength concerns with flow screed at 50mm, I assume it would be more prone to hotspots that relate to the embedded UFH pipe network. Thanks for the tip, something else to research.

I am trying to finalize the proportions of insulation/screed on the assumption that FFL is a full block above the level of the infill blocks of a block & beam suspended ground floor. My architectural technician has unfortunately depicted a 200mm high first course of blocks above the B&B floor. Is there a combination of insulation sheet that results in 160mm of depth that could then be finished with a relatively thick 65mm of flow screed with UFH pipes embedded to bring me up a full 225m high block?

I think you have just claimed a microwave cooker offers no advantage over a conventional oven. If the objective of a house heating system is not to illustrate Newtonian conservation of energy or Victorian vintage laws of thermodynamics but is instead the objective is happy content humans then the company might be offering an "efficiency" gain. The notion of graphene coated walls glowing with IR rays bathing householders is interesting, though I suspect, as with any graphene based product, the promise will never be fulfilled.