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    • CommentAuthorMarkyP
    • CommentTimeOct 19th 2017
     
    My EWI is finally underway. I'm going to post updates and photos of various details as I progress, may be useful for others considering an EWI project.

    first up, I'll kick off with the spec and a bit of background.

    I have an existing full fill 50mm wool cavity walls on a large bungalow. I'm upgrading with an additional 100mm of graphite EPS which will be render finished. I also have two further walls of 1.5 storey extension in medium density blockwork with 125mm full fill wool all built last summer. I've decided to EWI these walls as well, I realised as I went through the project that should have gone for a wider cavity. Also, while I watched like a hawk, the block gang were sloppy, and I dont doubt they've left me some gaps in the insulation. Also we used standard cavity wall ties and catnic type lintels, all adding a degree of cold bridging. I decided worth the extra cost and time to add another 100mm of EPS over the outside of the new walls, fixes all the cold bridging, and almost doubles the amount of insulation. I reckon this must be the first new build hybrid cavity/EWI wall in the UK!

    Why not thicker EPS? I could have done so, but was constrained by eaves overhang. Luckily we re-roofed, I was able to run new gable rafters to allow extra overhang clearance at the verge. I'm very happy with the prospective improvement the 100mm will offer.

    The EPS I purchased is Kay-Cel Super+ EWI. This is the graphite enhanced stuff with the lower conductivity. The boards are cut from aged EPS blocks, seems this is considered important for dimensional stability.

    The EWI system I'm using is made by Baumit. I've had a very good experience with their regional rep, and they have given me access to their field engineer to give what has so far been solid technical advice. They have a comprehensive EWI and render range, I'm using their StarContact white as an adhesive and basecoat, it's a cementitious product but different to many others in that it's lime enriched.

    I am planning to go below DPC with a plinth EWI detail. In the interests of time, I've run a base track and will carry out the above DPC works first to completion. The below DPC will follow as I just didnt have the time to dig down and break up existing concrete paths. I'm on a race against the clock to be ready for rendering before it gets too cold. I've used a Wemico starter track. It's PVC and comes in two sections, the base sits to the wall and projects, there's then a beaded/mesh insert which clips in once the EWI is fixed. I will form a drip detail here, probably with a 20mm inset to the below DPC insulation.

    that's enough for now, more to follow with various pics of some details so far.
    • CommentAuthorMarkyP
    • CommentTimeOct 19th 2017
     
    and one more thing. I'm doing all the prep and board fixing DIY, well DIY with a bit of help from a loacl lad I use for labour and a skilled alround tradesman who was interested in helping out for a few days to learn about EWI. Had intended to render myself but I'm up against the clock with winter coming and have found a reputable local renderer with experience of going over EWI who is going to do the finish for me. It's a cost I'd rather have avoided but necessary in the interests of getting to completion.
    • CommentAuthorgoodevans
    • CommentTimeOct 19th 2017
     
    Hi MarkyP - can you post a drawing with your DPC/plinth detail - are you using a different render below DPC.

    For my build I have EPS formwork for the slab/beam and cant decide whether to try and make it flush with the wall ewi - or create a plinth detail at the formwork/EWI interface - which way does your plinth go - recessed or projected?
    • CommentAuthorMarkyP
    • CommentTimeOct 19th 2017 edited
     
    plinth will be recessed by 20mm. As above, if I'd had time to do below DPC now, I would have run the same thickness continuous from footing to roofline, no base track, no DPC. However, trade foklore about DPCs is ubiquitous, all the EWI manufacturers show below DPC "plinth" details and bang on about importance of seperation at DPC level, etc. This doesnt seem to be backed up by science, it seems like the details they offerare the path of least resistance through trade folklore and building control dogma! I have not chosen plinth render yet, though struggling to see a reason not to use a generous coat of meshed base and whatever top coat I used above DPC. Will backfill with shingle to within aroudn 200mm of the DPC line, but no proper french drain as we sit on a chalk slope, drainage here is super. Note some manufacturer's specifcy XPS and waterproofing treatments below DPC, this seems utterly pointless to me so try to ignore those.

    IN your case, I'd be tempted to plan for a slightly recessed plinth. Saves you the headache of being accurate now in planning the exact thickness of EWI you use above, there are variables to content with which might conspire againt an easy flush union of the two layers - adhesive depth and if any walls run out of square, all could brew you a headache to make your above EWI meet flush with you EPS formwork. You may not need a starter track. You could lay a DPC on the formwork to make everyone relax abour DPCs and then lay the top layer EWI above, projecting. You can get a "push in" base bead, slides between the two layers, squirt of foam would hold it and make the joint sound.
    • CommentAuthorMarkyP
    • CommentTimeOct 19th 2017 edited
     
    here's the first pic. Nothing very exicting happening here. But the hot knife cutter (about £50 on a popular auction site) was well worth the spend. Takes some practice but cuts well using a timber straight edge as a guide without filling the garden with hundreds of tiny EPS beads. Another tip, a hot knife with a temp adjuster helped to find the sweet spot temperature, too hot and it smokes like mad and the knife wanders and creates much wider cuts. See the level in the background, despite having purchased aged EPS, some of the boards were bowed. These were set to one side and used for smaller cuts. Slight bows could be pushed flat and the adhesive held them so. The whippet in the foreground is of no use at all for applying EWI.
      IMG_0719.JPG
    • CommentAuthorMarkyP
    • CommentTimeOct 19th 2017 edited
     
    here's a detail i'm pleased with. When we replaced the roof we applied 11mm OSB sarking as an air tightness layer. I'm taking the EWI up the wall and between the rafters, and butted up to the OSB. I will foam around the joint between the OSB, rafters and EPS to form a good, air tight joint. The between rafter roof insulation will then be fitted tight to the inside of the EPS. The pic is a view up under the eaves where the soffit will be placed. Leaving a bit of eaves overhang was important to allow me room to get in with the foam gun later.
      IMG_0717.JPG
    • CommentAuthorgoodevans
    • CommentTimeOct 19th 2017
     
    Are you going for an adhesive only fixing option? - which adhesive are you using?

    If I went for a recessed plinth and push in base bead I assume the horizontal bit would not be rendered. do you have a link to what you are describing?

    We too have a dog that wishes to help - but is not very useful - I think it's the lack of opposable thumbs. You have the advantage in that your dog looks like it can get out the way fast.

    Is your hot knife for sale after you're done?
    • CommentAuthorMarkyP
    • CommentTimeOct 19th 2017
     
    I am using adhesive and mechanical fixings. I dont have the fixings yet. The adhesive is Baumit star contact white, same as the base coat. I used a bead of adhesive all around the edge of the board, three hand sized dabs in the middle.

    hot knife might be surplus once I'm done. Give me a nudge once the rendering is done and will let you know.

    the 20mm horizontal bit wouldnt be rendered.

    example of a base bead that pushes in https://www.wemico.com/pvc-base-profiles

    see bead 37500 which to my reading goes between the layers. The starter track part is only needed if you have no plinth.
    • CommentAuthorgoodevans
    • CommentTimeOct 19th 2017
     
    Yes that looks perfect - just need to get the bco to agree that a dpm/dpc across the eps creates a dam preventing save passage of unintended leaks getting to the ground - wish me luck.

    I fancied the spray foam with no mechanical fixings - I think that may be too brave.

    Is that hot knife work around the rafters - if so very neat.
    • CommentAuthorMarkyP
    • CommentTimeOct 19th 2017 edited
     
    I did consider the PU foam option, its appeal is now clear in that mixing up bags of adhesive and then applying it to each board is slow going. A squirt with the foam gun would have been much much faster.
    • CommentAuthorMarkyP
    • CommentTimeOct 19th 2017 edited
     
    here's a pic of the base rail prior to EWI going on. I went out in the dark the night before and used a cross line laser to mark a datum all along each wall to use as a reference to set the base track level. We did the odd check with a spirit level but the reference line really helped speed things up. The base track is from Wemico, it comes in two parts. The base track is fixed to the wall, the meshed bead is inserted into the base track after the EWI is fixed. The render above the base track had to be chopped back as was previously a bellcast bead drip detail, it projected 10 - 15mm beyond the rest of the render, so we removed it to allow us to set the EWI. The walls were all covered in a spray applied rough cast. It came off with a long pole scraper, bloody hard work but the rough cast was all over the place in terms of flatness, under it we found a lovely flat sand and cement render layer, perfect to set the EWI on, so worth the effort of stripping back the rough cast.

    It was well worth checking the walls for plumb before starting, we had a gable wall which was 10 - 15mm out of plumb, the top leaning out. Had we not known this we'd have fixed the base boards with 10mm adhesive and then as we set each course of the boards plumb we'd have got closer and closer to the wall, until eventually there would have been no room for adhesive and we'd have been trimming 10mm to make up 90mm thick sheets. As it was we knew to go a bit fat on the adhesive at the base and it thinned out as we went up the wall.
      IMG_0723.JPG
    • CommentAuthorgravelld
    • CommentTimeOct 19th 2017
     
    Great stuff, thanks for this.

    What's your detail for how you are treating the cavity at the eaves? Maybe less important as you have a warm roof.

    Why not tape for AT between OSB/rafters? Assume the existing render is the wall AT layer?
    • CommentAuthorMarkyP
    • CommentTimeOct 20th 2017
     
    the cavity is fully filled, both existing and on the new extension. Given the EWI will be taken up into eaves, detailed around the rafters and up to the sarking, I couldnt see much need to do anything with the cavities at the top. BCO was not fussed about me using closers at the top given full fill (seems it's mainly a fire detail from their point of view, for partial fill situations), and the cavities are going to be on the warm side, and inside the air tightness envelope, so I'm leaving them as they are. The roof insulation will be taken down between rafters and tightly fitted to the inside of the EPS, and over the top of the cavity insulation. Note not warm roof, planning full fill mineral wool between rafters, then PIR under rafters. No ventilation or void planned behind the sarking, relying warm side VCL, and the fact that OSB is relatively vapour open.

    what juntion would the AT tape serve in your proposa in my build up? Not sure I follow where you suggest it could be emplyed?

    existing render on the older part of the house does serve as AT layer to an extent, but the EWI with new render skin will be the main AT layer to the walls.
    • CommentAuthorMarkyP
    • CommentTimeOct 20th 2017 edited
     
    here's a pic of two elevations almost completely covered in the EPS. Fixing the boards was fairly slow going, but improved with practice. The first course is key, you need to ensure the first board is set plumb and also parallel to the wall, get that right and everyhting else follows nicely. On the parallel point, we set a board at each end of a run, and used a string line across them both to check they were running on a parallel plane. I think if you started at one end, and were running out just a few mm in parallel you'd see that amplify along the wall, or need to make a correction which would create a ridge or a dip. This probably wouldnt matter too much so long as it wasnt too big a correction but I'm a bit OCD and felt better taking the time to set things up.

    I have a 2.5m plasterer's featheredge which is handy for checking flatness across several boards, also a decent 1800mm level is really handy for setting each board as you go. As I went I checked each plane, horizontally and vertically, then after a couple of courses, check diagnolly as well. Across the whole gable there's very little variation shown under checks with a 2.5m straightedge, probably +/- 2mm, less in most places, which I'm happy with.
      IMG_0713.JPG
    • CommentAuthorgravelld
    • CommentTimeOct 20th 2017 edited
     
    Posted By: MarkyPwhat juntion would the AT tape serve in your proposa in my build up? Not sure I follow where you suggest it could be emplyed?
    For me, I don't trust foam long term to be AT (or rather, not the cured foam itself, but the adhesion). So therefore, where you have foam, I would probably have foam plus tape. Furthermore, I wouldn't have the EWI being part of the AT layer - this would be an "internal" (to the EWI) lining, e.g. the existing render, and tape to that. I think you can see the render on EWI as wind tight.

    But those are just my thoughts from research rather than actually doing and measuring.

    Why did you go for a "system" rather than just making the system up yourself?
    • CommentAuthorMarkyP
    • CommentTimeOct 23rd 2017
     
    I didnt plan on a system, originally intended to just pick the components from whereever. I bought the EPS seperately and also used a wemico starter track, but the fixings, basecoat, mesh, beads and fixings, finish coat are Baumit. The only reason I bought this all from Bauumit was cost, I wanted their render, I liked the lime enrichment, and when buying additonal components the discount was good, better pricing than I could have achieved buying bits seperately
    • CommentAuthorgoodevans
    • CommentTimeOct 23rd 2017
     
    MarkyP, can I ask how long it has taken to fix the eps so far including all the preperation bits such as creating a level line etc. So far that work looks pretty tidy - well done. How would you rate your handyman/building experience?

    Who is going to do the rendering?

    Can I also ask what was your price from Baumit (whisper if you prefer).
    • CommentAuthorMarkyP
    • CommentTimeOct 23rd 2017
     
    so far each elevation has taken about 1.5 to 2 days. I've been doing it either on my own, or with a local lad at the mixer and buttering up the boards for me while I do the cuts. To give an an idea of the pace, the gable you can see in the picture is about 22m2 and took 2 days. Angled cuts and working around reveals slows you down a fair bit. As does constantly checking flatness and level, but I want to make sure it's as flat as possible for the renderer.

    experience, I guess I'd say I'm a life long DIY'er. On this project I have done loads of work myself including bits of 1st fix joinery here including some roof framing, fitted my own windows doors, done a fair bit of blockwork. I'd say the fixing of the EPS boards is well within DIY reach. I was planning to to do the rendering (I can plaster to a good standard) but I dont have the time as winter is closing in and so am using a local reputable renderer. Found one who has worked over EPS before and comes highly recommended.

    contact Baumit and get in touch with your local rep. They will arrange you a pricelist/catalog for the EWI systems which is actually really comprehensive. The list prices are all shown so you can work out how much it will cost you. Obivously how much discount you can haggle will depend on your negotiation skills and the rep's keeness to make the sale! I can whisper you the discount I was given. I have added it all up yet, but should really work out how much this has cost per m2 at some point.

    it's worth spending some time building up a spreadsheet of the various bits and pieces you need, then go shopping to see what prices you can find, either individually or buying from a system supplier. Baumit seem quite happy to work with me, but some other EWI system suppliers were less keen once they realised it was my own project and I wasnt a builder. I have no affiliation but have been impressed so far with Baumit's support on the project, and the quality of their products.
    • CommentAuthorgoodevans
    • CommentTimeOct 23rd 2017
     
    Yes - please whisper the discount rate - Just getting to a ballpark discount rate is an achievement for me - my negotiation skill is pants - and my experience even lower.
  1.  
    Posted By: MarkyPAngled cuts and working around reveals slows you down a fair bit. As does constantly checking flatness and level, but I want to make sure it's as flat as possible for the renderer.

    Over here any EPS edges that are proud are sanded with something akin to a large wooden float covered with very coarse sand paper. This is flattens of any protrusions giving a flat surface for the render. It saves a lot of time when putting up the EPS especially if the wall is not too flat to start with as the odd 2-3mm (or more - oops!) projecting edge soon disappears. It does however create a bit of 'snow' in the process (grey in your case)

    For the renderer a 20mm dip over a couple of meters should not create a problem whereas a 2mm projecting edge would be a pain, you should see the wavy stone walls that I have had EWIed
    • CommentAuthorMarkyP
    • CommentTimeOct 30th 2017
     
    the advice I've been given is to rasp the EPS prior to rendering, both to remove any high spots and also because UV exposure makes the surface go a bit "crispy" over time. You can get a rasp for about £15 though they are a bit brutal. I found holding a saw blade flat to the EPS and dragging it over the surface worked well as a alternative. The renderer who will be doing my job said they didnt bother rasping and he'd never had a problem. But I'm going to give it a bit of a rough up in any case.
    • CommentAuthorMarkyP
    • CommentTimeOct 30th 2017 edited
     
    here are some more pics following this weekend's efforts. First up, some extension sills were fitted. My windows are new, Russell TimberTech, they were supplied with EWI in mind and came with a profile that was hammered into the timber sill which in turn allowed you to push fit the extension sill as pictured. I also spent a few hours with the foam gun, as you can see. all the EPS joints, regardless of size were foamed. It helps to tape a mastic gun nozzle over the end of the gun, this can be squeezed between the tightest of EPS joints.
      IMG_0739.JPG
    • CommentAuthorMarkyP
    • CommentTimeOct 30th 2017 edited
     
    next up some fixings. These were supplied by Baumit but they are manufactured by EJOT. They are the STR U-2G fixings and I've been impressed with them. First you drill an 8mm pilot hole to depth of the fixing plus 20mm. I chose a fixing which was taken 50mm into the underlying blockwork. The fixing is pushed in by hand until flat to the surface. Next up it is driven home using a special tool which cuts a clean recess and drives the fixing below the surface, the screw inside the fixing pulls the fixing into the wall and deforms the EPS forming a rebate, the tool has a guide which ensures the EPS deforms to form a cylindrical rebate. The screw head is well below the surface of the insulation at this point and the 20mm recess is finally filled with a ready made EPS cap which fits tightly. The fixing avoids cold briding and also helps keep the EPS surface flat, avoids the risk of "grinning through" the finished render had the fixings been on the surface of the EPS
      IMG_0740.JPG
    • CommentAuthorMarkyP
    • CommentTimeOct 30th 2017
     
    and here's the EPS cap. Baumit call it a "rondelle"
      IMG_0741.JPG
    •  
      CommentAuthordjh
    • CommentTimeOct 30th 2017
     
    That looks very professional, just like wood plugs to cover screws. Excellent.
    • CommentAuthorMarkyP
    • CommentTimeOct 30th 2017
     
    last pic for today. I've fitted my new windows partially outboard into the EWI zone. This is intended to reduce the size of the cold bridge of the window frame overlapping with the adjoining blockwork. I've fitted the windows such that they are approx 60% outboard by frame depth. Why not fully outboard? Mainly available EWI depth, I wanted to leave a small return for the reveal beads. Perhaps another reason I should have gone more than 100mm EWI.

    For the outboard mounting I used standard L-shaped angle brackets, heavy duty types. These are fixed to the side of frame and then to the face of the outside wall, adjustment in plumb of the window frame is done via packers before fixing to the block work. The bit of timber below the window is not part of the outboarding method, this was a rush job to provide a sub-sill when the top course of bricks on the reveal came out along with the previous window when I removed it (guess who forgot to remove the frame fixings from the sill of the old window before pulling it out?).
      IMG_0724.JPG
    • CommentAuthordelprado
    • CommentTimeOct 30th 2017
     
    Hi Mark would you mind sharing baumit rep details? I plan to use their render system on my house

    Thanks
    • CommentAuthorMarkyP
    • CommentTimeOct 30th 2017 edited
     
    Posted By: delpradoHi Mark would you mind sharing baumit rep details? I plan to use their render system on my house

    Thanks


    PM'd
    • CommentAuthorgravelld
    • CommentTimeOct 31st 2017
     
    Thanks for your ongoing updates.

    Can I ask: how did you create a window schedule? I'd like to know if it's sensible for an end user, with a hand in the design, to build this up from their own measurements (and also how a window schedule is supposed to be written).
    • CommentAuthorMarkyP
    • CommentTimeOct 31st 2017
     
    I sent drawings to the supplier and chose a window type, then they sent a draft schedule. We then iterated back and forth from there. Took hours and hours (or days and days) of my time to check and double check each window detail was correct. I also triple checked every opening for size as the architects drawings were not accurate in terms of exisitng opening dimensions. Based on my experience there's no way I'd put a large window order in the hands of a builder/main contractor. Maybe architect/designer who had experience of windows, especially if repeat experience of the supplier/product. I daresay some suppliers have a better, more actively managed specification/quotation process as well. I did it myself out of necessity rather than choice. I'm overall happy with the results, but with the benefit of hindsight I realise now I made a few bad decisions.
   
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