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  • Kevink
    started a topic waterproofing dome

    waterproofing dome

    Hi there, so we have been working away on our oven and are looking into the final coat for waterproofing.

    I'm locking at a 3/4 to maximum 1.5 inch coat of cement plaster (1 Portland, 0.5 lime, 5 to 9 sand). in this mix I want to add a waterproofing admix of some sort, ore put it on as is, and coat the outer shell with something like glasswater.

    we don't want to use a concrete waterproofing coating like you put on a driveway (at least we prefer not to make it a shiny dome)

    any other options or thoughts would be welcome.

    we are in Vancouver island Canada, no extreme winters but it hit sometimes -10C for a few days a year + it rains a fair bit in fall/winter.

    the oven was build as flow:

    1) 5 inch base with 3 layers of Re-bar (6x6 mesh)
    2) 4 inches of insulating concrete (perlite (3x) portland (1x) mix 1:3
    3) fire brick flat on bottom, with fire brick for dome sitting around it
    4) dome inside 44 inches inside diameter x 23 inch tall from inside, fire brick was secured with DIY mix of silica sand (3x) lime (1x) fire clay (1x) portland (1x)
    5) a few rows of red mason bricks, 6 inches from the fire brick
    6) fill void between firebrick and red mason brick with perlite (3x) portland (1x) lime (0.5x)
    7) insulating dome with perlite (3x) portland (1x) lime (0.5x) mix -- thickness of this insulating mix - side and top - 10 to 12 inches

    8) waterproofing topping ? (3/4 to 1.5 inch thick)

    any suggestions ??
    Last edited by Kevink; 09-02-2015, 02:36 PM.

  • millerlake
    replied
    Worked well left out in rain lots of times during summer
    Covered in winter (at cottage so unused)

    In the end I used the flexcrete but before tiling I decided to a full coat of Mapei AquaDefense on it
    Then 1" tiles using Kerabond/Keralastic
    grout with Mapei UltraColor Plus FA

    so everything is polymer based
    goal is nothing is getting in there

    probably still buy a custom tarp to cover in times when not there (ice is just such a worry in winter, don't want to have to rebuild anything)

    going to submit a build thread eventually chronicling all the fun work, decisions etc
    just about done (ran out of black tile ... oops)

    Last edited by millerlake; 08-25-2018, 07:34 AM.

    Leave a comment:


  • ASPLM
    replied
    So last post is two years or so ago, but how did the flexcrete solution work out? Iím in Portland Oregon, looking at a tiled igloo finish on a Casa 90.

    Leave a comment:


  • millerlake
    replied
    I ended up using Flexcrete (+polymer) from Lowes here (valcon industries) waterproof/breathable/flexible
    seemed to tick all the right boxes
    now to tile (well next year now)

    Leave a comment:


  • david s
    replied
    Most proprietary cement renders are partially waterproof. You wil probably notice some difficulty to get to water mixing into the dry product when first beginning to mix it. This means it has got waterproofing in it. You can also add some acrylic additive like Bondcrete around 1 part to 2 parts water when mixing. This makes the render stronger and more workable. A 100% acrylic render which comes wet in a bucket not dry in a bag, can be applied over the cement render after it has cured to make it completely waterproof. I find it easiest to water the stuff down 20% so it can be painted on.
    One school of thought is that the outer shell should be slightly porous so that moisture can escape through it. If completely waterproof the moisture will be locked inside. I prefer to make it completely waterproof and allow the moisture out via my vent.
    Last edited by david s; 08-08-2017, 03:12 PM.

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  • hofk@shaw.ca
    replied
    Just getting to the finishing stages of my igloo design. I'm wondering if using Specmix mortar (Portland,lime and sand )which is a brick mortar and supposedly waterproof would work as a waterproof final layer

    Leave a comment:


  • johnnybrewmeister
    replied
    Originally posted by millerlake View Post
    So this is all very interesting for me (trying to finish off last years project)
    Finish: igloo and mosaic tile
    Weather: Ontario Canada, so ice/snow in winter and rain of course
    Likely will cover with tarp in winter

    So current state is covered in matrilite19
    I think the tile will be kerabond/keralisic dryset (ultraflex3 thinset)+ glass tile

    So questions would be to make it as waterproof/breathable/crack resistant as possible
    options any/all/some of
    1 just add a scratch coat, tile, (seal?)
    2 add vent(s) through to theCFB (top or sides would it really matter sure top might be better but need to figure out the right vent o no water issues?)
    3 add a real wterproof layer of something like aquaDefense/redguard/ mapei smart + vent
    4 or maybe add that waterproofing at the top 1/3 and bottom 1/3 leaving a slightly more breathable mid section where water will run off anyway
    5 some other cementitous waterproof/breathable layer before tile? type-N concrete I think I saw is what Francis used?

    any ideas and even better specific product recommendations would help
    going back and forth on what to do

    photo before CFB & matrilite layers

    in hind-sight and if I had a chance to do it all over again, I'd choose option #4 - basically waterproof most of it, but leave plenty of ventable area. I think by doing this you could probably keep out 80-90% of the water, and would have no problem with it drying back out (either via time or warming fires).

    Leave a comment:


  • millerlake
    replied
    So this is all very interesting for me (trying to finish off last years project)
    Finish: igloo and mosaic tile
    Weather: Ontario Canada, so ice/snow in winter and rain of course
    Likely will cover with tarp in winter

    So current state is covered in matrilite19
    I think the tile will be kerabond/keralisic dryset (ultraflex3 thinset)+ glass tile

    So questions would be to make it as waterproof/breathable/crack resistant as possible
    options any/all/some of
    1 just add a scratch coat, tile, (seal?)
    2 add vent(s) through to theCFB (top or sides would it really matter sure top might be better but need to figure out the right vent o no water issues?)
    3 add a real wterproof layer of something like aquaDefense/redguard/ mapei smart + vent
    4 or maybe add that waterproofing at the top 1/3 and bottom 1/3 leaving a slightly more breathable mid section where water will run off anyway
    5 some other cementitous waterproof/breathable layer before tile? type-N concrete I think I saw is what Francis used?

    any ideas and even better specific product recommendations would help
    going back and forth on what to do

    photo before CFB & matrilite layers


    before CFB & matrilite layers

    Leave a comment:


  • johnnybrewmeister
    replied
    Dave, now *that's* a cool roof! I can't imagine getting that much rain, especially since we only get 8-12" per year on average. Since we're on the drier side of things, I'm planning on just dedicating a good waterproof tarp to sling over the oven whenever serious (if I can call it that) rain is forecast. Gotta love this forum. A lot of folks probably don't realize how truly valuable all of the old (even really old) posts can be, especially pictures, and especially to people like me that search & troll A LOT learning tons from others. Thanks!

    Leave a comment:


  • david s
    replied
    Originally posted by johnnybrewmeister View Post
    Thanks Dave for the PM, and others for the details. So regarding the vent tube, it seems that if I did seal the dome with something like Tyvek, then a vent tube would be a smart idea. But if I don't seal it (which is where I'm leaning), since stucco passes water (and therefore water vapor), then there would be no need for the vent tube - the whole stucco dome would vent.
    Sorry if I'm being thick-skulled here, but at least I'm learning alot.
    Yes, that's right. Probably the best situation is to leave the outer shell unsealed, but have a roof over your oven. The problem with that solution is that it takes more expense and time which maybe more than you wanted just for an outdoor cooker. My oven is in the weather and after heavy rain and humidity (we live in the tropics), the oven gets wet and needs a few fires to dry it out. In fact even if it hasn't rained but the humidity is really high for a prolonged period with no oven use, the thing is still damp and the insulation is not as effective, ie it's hot to touch on the outside rather than just cosy warm. I'd prefer to dry it out a bit rather than build a dedicated roof though, especially as you have a flue pipe penetrating a roof. Or you could build one of these.https://community.fornobravo.com/for...670#post395670

    Dave
    Last edited by david s; 03-21-2017, 04:03 PM.

    Leave a comment:


  • johnnybrewmeister
    replied
    Thanks Dave for the PM, and others for the details. So regarding the vent tube, it seems that if I did seal the dome with something like Tyvek, then a vent tube would be a smart idea. But if I don't seal it (which is where I'm leaning), since stucco passes water (and therefore water vapor), then there would be no need for the vent tube - the whole stucco dome would vent.
    Sorry if I'm being thick-skulled here, but at least I'm learning alot.

    Leave a comment:


  • UtahBeehiver
    replied
    Vents in dome
    Gastagg
    David S
    Gulf
    Utahbeehiver - me
    a host of others but can't recall exactly who.

    But this is up to you. Since I believe you are not enclosing the oven in a structure and the dome will be seen you are probably wanting to minimize potential cracking of the stucco. Both Gulf and I and several inches of p/v-crete over our CFB so there was water to get removed.David's is vent is unique since it is built in the vent stack. Gastagg's is some copper tubing near the front of the dome.

    Leave a comment:


  • david s
    replied
    I've only just seen the OP on this thread and as it's over two years old any advice is presumably too late, but for anyone following this build, remember that perlcrete or vermicrete takes around a third of its volume in water and less than half of that will be used up in the hydration process leaving you with an enormous amount of water to eliminate. You can calculate that for a 6" layer but it's enormous. The beauty of CFB is that it's dry so you don't need to remove any water from it. If the insulation is enclosed the perlite can be added loose and dry and will be a better insulator. At 3:1 you are making the density four times greater than the loose perlite and reducing its insulation by around the same amount, so a doubly bad idea.See attached experiment on drying vermicrete.

    Vermicrete insulating slab copy.doc.zip
    Attached Files

    Leave a comment:


  • david s
    replied
    John,
    I've pm'd you. Take a look at Gulf's thread.
    Dave

    Leave a comment:


  • johnnybrewmeister
    replied
    Thanks guys for the info. Very interesting...if the CF blanket doesn't swell when wet, then I am much less concerned about the stucco dome not being waterproof. Less worry is a good thing. Strange that this is the first I'm hearing about a vent tube into the dome, and I've been trolling this forum for years, and working on this build for almost 2 years (built a "practice" oven before this real one). Since you mention Dave's vent specifically, I will see if there is a build-thread that shows this. Do most people include a vent? (sorry if my ignorance is showing here).

    Regarding Tyvek in-between stucco layers, I was basically going to ignore the existing thin scratch coat - that is, thinking of adding Tyvek layer, then adding more wire, then do another scratch coat, followed by brown and finish coats.

    Is it bad if the CF blanket repeatedly goes thru wet/dry cycles?

    Leave a comment:

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