Pocster Posted February 18, 2018 Author Share Posted February 18, 2018 (edited) 54 minutes ago, SteamyTea said: @pocsterI am a bit tied up at the moment, but shall come back and give my thoughts on how to do your layup. Any chance that you can post a picture or sketch up of the two run off areas and any these up stands. It may help clarify what you are trying to do. Basically GRP is easy to put into a corner/edge, harder to put over a corner/edge. Bondage on a Sunday ? Here's a *rough* site plan. The drainage channel's will be added after i.e sit on top the EDPM/GRP. 'Path" and the wall are 'outside' the below ground construction. Another issue (there are so many!) is I really need to gain height!. At the house from current slab to build is 38cm, at the front (entrance via gate) is 18cm. If OSB is required whether GRP or EDPM that looses another 18mm!!. Tempted (without telling architect!) to put zero insulation in (to save height). Would insulate underneath i.e. in ceiling with celotex or if ceiling height becomes an issue aerogel (ignoring the £££££). I *assume* that altering that insulation layer wouldn't be an issue (MHVR so presumably no condensation issues). Saves me 50mm 'moving it'...... Any views on that appreciated also. Strangely enough companies that only sell GRP recommend that; companies that only sell EDPM recommend that - how strange! Edited February 18, 2018 by pocster Link to comment Share on other sites More sharing options...
Barney12 Posted February 18, 2018 Share Posted February 18, 2018 3 hours ago, JSHarris said: I'd wholeheartedly agree with @SteamyTea. CFS do some good roofing kits, I've used a lot of their stuff over the years, and for this job I'd be inclined to give them a call for advice. My experience has been that they are very clued up and happy to help, but I'll caveat that by adding that my nephew worked there for years. Here's a link to their roofing section: https://www.cfsnet.co.uk/acatalog/CFS_Catalogue__FLAT_ROOFING_21.html They have some guidance on roofing with GRP here: https://www.cfsnet.co.uk/acatalog/1project-roofs.html but I would be inclined to ask them about your specific requirement, where you're laying concrete on top of the GRP, as the choice of resin may be more critical. I agree with ST that vinyl ester resin would seem to be the best bet. Another vote for CFS. Excellent company to deal with. Link to comment Share on other sites More sharing options...
Pocster Posted February 18, 2018 Author Share Posted February 18, 2018 30 minutes ago, Barney12 said: Another vote for CFS. Excellent company to deal with. Will call them ! Still not diy ing it though ☺️ Link to comment Share on other sites More sharing options...
mvincentd Posted February 18, 2018 Share Posted February 18, 2018 8 hours ago, pocster said: and where the original pour has shrunk ...so you already have the lower layer of rc in place. https://www.sikawaterproofing.co.uk/products-systems/sikaproof/sikaproof-p-post-applied-fully-bonded-membrane-system/ Link to comment Share on other sites More sharing options...
Pocster Posted February 18, 2018 Author Share Posted February 18, 2018 (edited) 13 minutes ago, mvincentd said: ...so you already have the lower layer of rc in place. https://www.sikawaterproofing.co.uk/products-systems/sikaproof/sikaproof-p-post-applied-fully-bonded-membrane-system/ Yep ! but I’m scared !! Do these things and it leaks all fingers will point at me . “ didn’t do edpm “ didn’t do “ grp “ .... etc .... ? Also to get “installed “ professionally ( ie not a edpm or grp roofer ) will cost more . Keeping to ‘ conventional ‘ methods makes everyone happier ( and cheaper ! ) Edited February 18, 2018 by pocster Link to comment Share on other sites More sharing options...
Onoff Posted February 18, 2018 Share Posted February 18, 2018 3 minutes ago, pocster said: Yep ! but I’m scared !! Do these things and it leaks all fingers will point at me . “ didn’t do edpm “ didn’t do “ grp “ .... etc .... ? Ridicule is nothing to be scared of... 1 Link to comment Share on other sites More sharing options...
PeterW Posted February 18, 2018 Share Posted February 18, 2018 20 minutes ago, pocster said: Keeping to ‘ conventional ‘ methods makes everyone happier ( and cheaper ! ) What you are doing is far from conventional ..! The conventional method is the waterproof membrane method and then additional concrete, what GRP and EDPM are designed as are final finish layer. Link to comment Share on other sites More sharing options...
Pocster Posted February 18, 2018 Author Share Posted February 18, 2018 18 minutes ago, Onoff said: Ridicule is nothing to be scared of... But the shame !!!! ? Link to comment Share on other sites More sharing options...
Pocster Posted February 18, 2018 Author Share Posted February 18, 2018 Just now, PeterW said: What you are doing is far from conventional ..! The conventional method is the waterproof membrane method and then additional concrete, what GRP and EDPM are designed as are final finish layer. I have found quite a few ‘balcony’ type arrangements with concrete on edpm for extra strength . But yes ; it’s not the standard . But who wants a standard house ? Link to comment Share on other sites More sharing options...
SteamyTea Posted February 18, 2018 Share Posted February 18, 2018 On 2/17/2018 at 18:31, pocster said: reinforced concrete high compressive insulation osb ? If using edpm or just grp reinforced poured concrete chippings sand driveway blocks Just had a look at your build up, any change of putting some measurements onto it. I am envisaging a platform to park cars on. The platform is built over something. Is that right? As the GRP is only for waterproofing, it could go onto thinner board, possibly 3mm ply. It is really only to make the lay up easy and stable. I don't think it is there to add anything structural. I can see where the wall is and the drain challenges. It would be usual to have the drainage built into the platform. Is there walls either side of them and that is why are two of them. A 3D sketch may be more useful as I am struggling to understand it. How high up do the skylights stand. As long as there is 100 mm, then bonding to that should not be a problem. Does depend on the radii at the corners. There are ways around that though. Link to comment Share on other sites More sharing options...
Pocster Posted February 18, 2018 Author Share Posted February 18, 2018 2 minutes ago, SteamyTea said: Just had a look at your build up, any change of putting some measurements onto it. I am envisaging a platform to park cars on. The platform is built over something. Is that right? As the GRP is only for waterproofing, it could go onto thinner board, possibly 3mm ply. It is really only to make the lay up easy and stable. I don't think it is there to add anything structural. I can see where the wall is and the drain challenges. It would be usual to have the drainage built into the platform. Is there walls either side of them and that is why are two of them. A 3D sketch may be more useful as I am struggling to understand it. How high up do the skylights stand. As long as there is 100 mm, then bonding to that should not be a problem. Does depend on the radii at the corners. There are ways around that though. ? I’ll attempt ! reinforced concrete : this is done high compressive insulation : only 50mm ( meant to be 120mm ) causes me issues anyway osb ? If using edpm or just grp : this will add 20mm reinforced poured concrete : SE wants 75mm chippings : whatever :-) sand :-) whatever driveway blocks : 50mm as you can see 180mm at the front is an issue . upstands ; well glass is 64mm ; so 100mm for up stands min . grp or edpm not structural . nothing either side of drainage channels . One near the house to ‘protect’ it ; other to deal with run off from sloped finish . cheers Link to comment Share on other sites More sharing options...
SteamyTea Posted February 18, 2018 Share Posted February 18, 2018 The way I see it then is that the GRP is just waterproofing. So can be put directly onto the insulation. If that insulation is glass tissue covered. 3 layers of 450 gm.m2 matt with a flow coat will do that as the strength is in the reinforced concrete pour above it. There will need to be some detailing for the drainage channels, but that would need some more information as to what you want it to look like. With the final reinforced slab being 75mm thick, bolting the balustrade to it may be a problem. Is it possible to have some plates with threaded studs fitted into the correct place (I was a toolmaker, not a builder so working to 1000th of an inch is normal to me). Or you could have plates fitted and then drill and tap after (probably safer). That would need a structural engineers input. At the interface of the drainage channels and the reinforced concrete below it I would fit a pre moulded section. Probably make the interface and the 'gutter' as one, then lay some GRP over it. I am not sure how they would detail with with a rubber sheet, sorry EDPM, but suspect that they would do something similar. What are the overall dimensions? Some consideration may be needed for thermal expansion. Link to comment Share on other sites More sharing options...
Pocster Posted February 18, 2018 Author Share Posted February 18, 2018 7 minutes ago, SteamyTea said: The way I see it then is that the GRP is just waterproofing. So can be put directly onto the insulation. If that insulation is glass tissue covered. 3 layers of 450 gm.m2 matt with a flow coat will do that as the strength is in the reinforced concrete pour above it. There will need to be some detailing for the drainage channels, but that would need some more information as to what you want it to look like. With the final reinforced slab being 75mm thick, bolting the balustrade to it may be a problem. Is it possible to have some plates with threaded studs fitted into the correct place (I was a toolmaker, not a builder so working to 1000th of an inch is normal to me). Or you could have plates fitted and then drill and tap after (probably safer). That would need a structural engineers input. At the interface of the drainage channels and the reinforced concrete below it I would fit a pre moulded section. Probably make the interface and the 'gutter' as one, then lay some GRP over it. I am not sure how they would detail with with a rubber sheet, sorry EDPM, but suspect that they would do something similar. What are the overall dimensions? Some consideration may be needed for thermal expansion. Thanks balustrade??? Lol there isn’t any ? I did suggest to the Architect to cast the drainage channel in situ ; but he wasn’t happy and wanted standard anco type product .haunched ontop the grp and obviously flush with finished level . total area is question is approx 6m x 6m cheers Link to comment Share on other sites More sharing options...
SteamyTea Posted February 18, 2018 Share Posted February 18, 2018 Is it something like this? Link to comment Share on other sites More sharing options...
SteamyTea Posted February 18, 2018 Share Posted February 18, 2018 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 19, 2018 Share Posted February 19, 2018 Just a word of caution if this roof is over an inhabited part of the house. The insulation thickness specified will have been driven by the requirements of Part L1A, and if you replace 120mm with 50mm then you may find that you can't get an acceptable SAP outcome, and that could mean taking the whole lot up and fitting the proper insulation thickness, or, perhaps, adding more insulation on the ceiling beneath. 120mm of PIR insulation just meets the minimum fabric requirements of Part L1A, 50mm of PIR definitely does not, so would be a breach that your building inspector might well spot visually, before you got as far as doing the as-built SAP. Link to comment Share on other sites More sharing options...
Pocster Posted February 19, 2018 Author Share Posted February 19, 2018 9 hours ago, SteamyTea said: Exactly !! Link to comment Share on other sites More sharing options...
Pocster Posted February 19, 2018 Author Share Posted February 19, 2018 3 minutes ago, JSHarris said: Just a word of caution if this roof is over an inhabited part of the house. The insulation thickness specified will have been driven by the requirements of Part L1A, and if you replace 120mm with 50mm then you may find that you can't get an acceptable SAP outcome, and that could mean taking the whole lot up and fitting the proper insulation thickness, or, perhaps, adding more insulation on the ceiling beneath. 120mm of PIR insulation just meets the minimum fabric requirements of Part L1A, 50mm of PIR definitely does not, so would be a breach that your building inspector might well spot visually, before you got as far as doing the as-built SAP. Yes - the insulation thickness is an issue at 50mm . So there’s no problem if I ignore the insulation ; but insulate underneath - even thicker if I wish ?? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 19, 2018 Share Posted February 19, 2018 5 minutes ago, pocster said: Yes - the insulation thickness is an issue at 50mm . So there’s no problem if I ignore the insulation ; but insulate underneath - even thicker if I wish ?? Yes there could be, it depends on the make up. Ideally you want all the insulation in one place, as that tends to avoid issues with thermal bridging around the edges and possible interstitial condensation. Why not just follow the architects spec? He/she will have done all the calcs and chosen the insulation material and placement accordingly. Link to comment Share on other sites More sharing options...
Pocster Posted February 19, 2018 Author Share Posted February 19, 2018 14 minutes ago, JSHarris said: Yes there could be, it depends on the make up. Ideally you want all the insulation in one place, as that tends to avoid issues with thermal bridging around the edges and possible interstitial condensation. Why not just follow the architects spec? He/she will have done all the calcs and chosen the insulation material and placement accordingly. That’s the problem ! i haven’t got the depth to stick 120mm in . surely underneath I.e on the ceiling with MVHR condensation not an issue ?? Link to comment Share on other sites More sharing options...
Pocster Posted February 19, 2018 Author Share Posted February 19, 2018 High compressive structural aerogel would solve the issue - if it existed !! ? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 19, 2018 Share Posted February 19, 2018 Just now, pocster said: That’s the problem ! i haven’t got the depth to stick 120mm in . surely underneath I.e on the ceiling with MVHR condensation not an issue ?? It may well be big issue if you put that inside insulation under the vapour control layer! Very much better to try and find a way to stick to the architects specification if you can, as that looks to be risk-free and straightforward. If you add around 100mm (and it will probably need to be around this thickness because of the increased thermal bridging caused by only having 50mm above the first concrete layer) then you will then need to also add a vapour control layer (VCL) underneath it, sealed carefully to the wall VCL, with the service void and plasterboard ceiling under that. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 19, 2018 Share Posted February 19, 2018 (edited) Could you get the underside/inside sprayed with PU foam, then put in a VCL if needed. Then you can pour a secondary reinforced slab onto the existing one. Seems to me that the GRP/EDPM is just there to protect the insulation/chipboard. Edited February 19, 2018 by SteamyTea Link to comment Share on other sites More sharing options...
Pocster Posted February 19, 2018 Author Share Posted February 19, 2018 Sticking all the insulation underneath does help ! . I’ll call my architect - but he’s always unhappy if it hasn’t “ gone to plan “ ..... Link to comment Share on other sites More sharing options...
Pocster Posted February 19, 2018 Author Share Posted February 19, 2018 Architect says no way to chip board / osb I did think this seemed bad in a concrete sandwich !! unhappy with insulation on ceiling !!! its effectively a warm room structure - so must keep to that ! Link to comment Share on other sites More sharing options...
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