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Hi everyone, We're adding ~300mm external wall insulation and render to our 70s terraced house (looking to achieve EnerPHit, hence the especially thick EWI), and we're trying to find some information on cavity trays and weepholes. What we know: In at least one instance, we have a sloped lintel which acts as our cavity tray. There are no noticeable existing weepholes above any of the openings. Based on the "Weepholes" section of https://nhbc-standards.co.uk/6-superstructure-excluding-roofs/6-11-render/6-11-7-detailing/, we think that we don't need weepholes since we are in a moderate exposure zone (Stockport). Our questions are: If we have interpreted the above guidance correctly, would that mean it doesn't matter if our cavity tray doesn't have stop ends (we believe these may be missing)? Similarly, considering the questionable build quality, we're not certain if the meter boxes or if all the other openings in the external wall are fitted with cavity trays. Would cavity trays even be needed if we are installing EWI and render? Would appreciate some advice on the above, or if anyone has done similar work please tell us how you did it! Thanks all

Branching off from my Little Brown Bungalow thread, I am doing EWI which will probably be 90-120 EPS and a thin film render, to give me a U-Value for the wall of between 0.19 and 0.23. Good so far. But I have a number of questions about "how to do" to make sure I get the detail right, and I thought it would be a good separate thread so others can pile in their Qs in future. Over at the Green Building Forum (GBF) there is an extensive literature of scores of threads about this, but digging there is like excavating Troy with a toothpick. Hence this focused thread. These are my current queries: 1 - How to Mount things on the outside of the EWI There are three categories - a) - light things (say less than 5kg), b) heavy things (5kg+), (c) really heavy things (eg porch canopy). (a) might be something like an outside light, while (b) might be something like a satellite dish. What are the current suggested best practice for this? (a) used to be "drill a 25mm hole with a shovel bit, insert a piece of pipe, fill with a stronger gun-foam, and plug/screw into that". Or alternatively to "insert and glue a plug of stronger insulation, such as a different grade EPS or Extruded Polystyrene, and mount into that". I note that there are now "EWI Spiral Insulation Anchor" fittings, like large versions of plastic plaster spirals and claim 5kg capability. (b) used to be "accept the cold spot and drill into the wall with a long fixing", but I have also seen "insert a batten or sheet of plywood under the insulation when doing it". My preference is for an alternative - eg provide a 6" diameter 6" post elsewhere for a satellite disk and a precreated cable route inside. (c) has usually been "use lighter anchors and a post against the wall that passes the load into the ground" or "freestanding post" Clearly the more complex it is made at the beginning the more cost that will be added to the install up front, but that is probably worthwhile to avoid complications later. This is the best thread I have seen over at GBF: External fittings on EWI. 2 - Gas and Electric Meters Separate thread here.: Shallower Gas Meter Boxes. 3 - Ventilation via Ceiling rather than Fans On the "minimise holes in EWI" principle, I plan to take these out through the roof. Are there any difficulties or limitations on taking bathroom and kitchen extract fans (probably not the Hob Extractor Hood) out through the ceiling and a ventilation tile, other than length of duct run etc? I need a model of heat recovery fan that will do this (usually I use through the wall Vent-Axia Lo Carbon Tempra models). 4 - Gas flues I know nothing about this wrt EWI. My small bungalow does have an old flue which goes up to a chimney. Can I use this for my boiler exhaust etc? I suspect that it will not meet the modern inspection requires for Gas Flues (ie hatches everywhere). I think I can find a way around this reasonably easily. 5 - Controlling mad men with drills (Hello Virgin) This is tricky since my property will be rented. I need to stop the visiting driller killers from putting holes in my nicely warm and airtight walls. I can do things such as a clause in the rental contract, tenant education etc - that will work with longer term tenants. I suspect the best way will be that plus a pre-determined duct with a drawstring coming (eg) into an airtight, insulated built in cabinet in the appropriate location. Another option is to have the cable runs in place first. I would be most interested to here comments or variations on any of the above. Thanks Ferdinand