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Hi Will, happy to help. On the primer, it depends on the membrane. Some self adhesive VCLs need primer over the whole deck to get a reliable bond, while others are made to go straight onto clean, dry OSB and only want primer at laps, edges or in cold weather. The other route is a loose laid or mechanically fixed VCL with taped laps, sealed to the wall airtightness line at the plate. That's quicker and cheaper on a big roof, and because the counter battens clamp everything down it works well as long as the laps and junctions are taped properly. Check the datasheet for whichever product you pick, as primer requirements and minimum application temperatures vary a lot. On slippage, you're thinking along the right lines. A continuous timber stop at the eaves, the full depth of the insulation and fixed back through the deck into the rafters, gives the bottom row of boards something solid to bear on. After that, the counter batten fixings do most of the holding, so the fixing design matters more than anything else. Get the screw manufacturer to calculate spacing, length and angle for your pitch, insulation depth and roof loads, including snow and the weight of the tiles or slates. Some systems use screws angled up the slope, others use crossed pairs. Stagger the joints between the two PIR layers and keep the boards tight, so the load is shared and there are no gaps for vapour or cold bridging. And fix the counter battens as you go rather than laying a big area of loose boards, especially on a steep pitch or if it's breezy. A timber stop at the verges and ridge is worth having too, so the edges are closed off and there's something solid to fix the trims to.

I think there is a base for this. Like a fence post socket but with a central rod that gets epoxied into the foundation. Your way will work but be a bit unsightly perhaps. You will need to keep the bottom of the timber dry.

Ive not read the whole thread but is there a reason you overboarded with ply? I thought p5 was good stuff.

Buy a bung, fill system up, extend all pipes to 1m above ground and brace. Fill up to top and time the water. What stage are you up to?

Our BC wants to witness a water drain test. @Caroline is there a website you went to to understand how to do it? We’ve found somewhere that hires the bing kit out for £40, so we’d like to do it ourselves if we can.

Yes, that's the downside - maybe don't park the car inside the carport April to September!

Very good point, thanks. I was thinking of Simpson Strong-tie with a four point fixing and chemical anchors but I will see what the SE says. I assume he will offer up a minimum lift resistance I have to meet which I could compare against the chemical anchor rating - might not need all 4 anchors in place to meet the requirement.

Hmm, I was thinking the self regulating PTC kind. Just looked at the link and this type is controlled by a thermostat. Might be a bit difficult with insulation then. TLC seem to sell the self regulating kind on the same page, but then looks like you need to do the termination yourself which is a bit more involved than normal domestic electrics.

Yes, that's how most were done.

And then insulate the pipe with the heating tape on the inside

Just put a trace heating tape on the pipe. Used to see loads of them on the taps on high rise roofs. Something like this: https://www.tlc-direct.co.uk/Products/BNPW01.html

Have you seen the plastic box that sits in the ground, the tap is underground as well as a roll of house pipe all enclosed in the plastic box.

I would dearly love to have a freestanding tap in the garden, but is it worth the effort required to stop it freezing. But I hate taps on the wall. Frostline taps have some self draining mechanism to stop them frosting up but still require a nearby valve in the ground. If I need to put a valve in the ground then I may as well just install a regular free standing tap and then a drain valve in a nearby box to drain it in the autumn. Bernard the builder is already rolling his eyes over this, what to do?

Gotcha, it's solid as in 22mm P5 with 6mm Ply glued and screwed. It says on the back of the container that it must be dry before adhesive, which is kinda the opposite to what I've read on here where it needs to be "tacky". I've just found a tech sheet from UltraTile SPES that says to apply it neat on plywood before adhesive as well, so that's 3 options! 🤣 Happy to go with professional plumber experience with this one though 👑

This is an external door installed onto XPS with EPDM as the DPM. The EPDM was left long on the inside. I turned it up at the sides in case it was needed. It's an ICF build with Waterproof concrete and no conventional DPC. It's an RK door with a skimpy low threshold, almost non existent upstand. The floor is Block & Beam, there is a 1200ga DPM under the PIR, this is what you can see in the image laying back onto the PIR. This is with the EPDM lifted. The inner threshold is 50mm below the door threshold, but still XPS. The screed needs to come up almost to the underside of the threshold, with 3-4mm Microcement as the final finish. How should this detail be finalised? Should these membranes just be taped together? Any expansion joint along the threshold? There's another 80mm of PIR to go on yet, this will bring it level with the blue XPS, with everything 50mm below final FFL. I have 2 more Norrsken doors following roughly the same principle. As always, your help is invaluable to me, and I'm procrastinating on it at the moment!

If it's a solid deck then you'll be good to just have a damp sponge in the dilute mix, and use that 1m2 at a time as you're laying, just to stop the surface from being 'dry' when the tile adhesive hits it.

I'm in exactly the same boat myself, so watching with interest. I figure a battery and AC inverter standalone, doesn't interact with my PV and the FIT meter which monitors them... So I hope not an issue!

@Gus Potter @ADLIan @JpManning @Stu789 Many thanks guys for the swift responses and warm welcome, much appreciated. Feels like general consensus is one's needed but with varying degrees of how critical it is by sounds. I reviewed some of the warm flat roof material and it makes sense to me especially when you have an impermeable layer of epdm above, I suppose the concern if I'm understanding correctly is that the pir could cause that issue albeit it the breather/waterproof membrane above pir would potentially let some of it out... I checked out the alutrix 600 and note it needs a fluid applied primer for it. Is there anything that doesn't require going over the whole roof with primer or is this just a necc evil? With regards to stopping the slippage...is there methods that you recommend? Id heard about creating a solid fascia type upstand which would essentially act as a stop for the pir boards. And screws being driven in at the correct angle....anything else worth thinking about? Thoughts appreciated Will

Does this still l hold true for tiling @Nickfromwales? I'm going for porcelain over 6mm plywood (which is over chipboard) already glued and screwed. I went over it with Ultra primer 3:1 mix last night, should I go over over it again just before I start to mix up my adhesive? Instructions on the container are ropey at best. Advice welcome.

probably 15 years. I'll give them all an airing, but generally it isn't a problem. This radiator did leak from a valve for a while so may also have been letting in air there or elsewhere.

I didn't explain myself very well. They put up the end frames and a couple of frames in the middle using muscle, braced them, and then used a crane to drop in the intermediate frames. We had some dormers, so some of the frames were odd shapes.

I like this approach and for me a most enjoyable part of the build. Myself and help from my Dad, 75 years old stick built my self build. This is half of it.

Often nails are structurally superior to screws. Think of them as bolts, just that you cannot adjust them with a spanner (but you can with a hammer). That is why they sold it to a Limey. It can seem strange to use that the VCL is on the outside.

Infill frames around where windows are? A requirement that could be designed out with some thought. I think I've seen (online) something done whereby you build every frame the same, stand them, brace them (even board them). Then come back and infill support structures around windows (cutting the required i-joists then adding lintel support in one operation). Do it that way and you get a protected shell in very short order and then cut in access. But it might be my memory confusing this for something else.

It's fairly common, and it usually tells you more about the system than about that one radiator. Pressed steel rads nearly always fail from the inside, and the top is the classic spot because that's where air or gas collects. Steel sitting in that pocket with a film of moisture on it corrodes much faster than steel below the waterline, and inhibitor does very little up there. So the real question is why there was a pocket at the top. A few things worth checking before you worry about the whole house: How often do the other rads need bleeding, and is it a long hiss or barely anything? Rads that need bleeding every few weeks point to air getting in, or gas being produced by corrosion. When you drain the old one, look at what comes out. Black sludge is magnetite, which is normal wear and manageable with a magnetic filter and a clean. Orange or brown water suggests oxygen is getting in somewhere, and that's what eats rads. If it's open vented, have a look at the feed and expansion tank in the loft. A ball valve that's constantly topping up, or the pump pushing water over the vent pipe, keeps pulling fresh oxygenated water into the system. If it's sealed, think about how often you've had to repressurise it. Regular top ups mean a slow leak somewhere and fresh water going in every time. Get a sample tested for inhibitor level rather than assuming it's fine. Most inhibitor manufacturers offer a testing service, and a cheap dip test kit will give you a rough idea in the meantime. If the others rarely need bleeding, the water is black rather than orange and the inhibitor reads OK, I'd treat it as one tired rad (how old is it?) and just replace that one. If several bleed often and the water is rusty, it's worth tracking down the air ingress first, otherwise the new rad will go the same way.