opinions on techniques for dome waterproofingr

[merlyn]

Greetings,, I live down on the gulf coast of alabama.and we get a lot of rain and the occasional hurricane . I would like to just have a dome structure with out the roof . I can build a brick house around it but would rather not . why? because it is part of a over all out door area including a smoker grill and a large fireplace . We like the idea of the round shape with the other square shapes . Also I`d go with a metal roof and wind goes around the dome shape better , . Ok that said here`s my plan ..
Fire brick with ceramic blanket then the vermiculite concrete some chicken wire over that . Now add about 1 inch of mortar over that,,on this I will apply 4 coats of the plastic coating they apply to swimming pools it is a thick paint like substance . Over this a double layer of aluminum foil , then 1 more chicken wire ,1 more layer of mortar . At this point I `m done or I could repeat the process of aluminum and paint or use some type of final coat over the mortar .. I will extend the water proof paint out at least 4 inchs around the base in the 1st coating as to protect the 4 inchs of fiber board .. I`m a firm believer in over engineer it first so you don`t have to try and fix it latter ..!!
So any advice on what you think or a different process to use would be really appreciated .. Laugh when you can life is to short to be anything but happy !!
Merlyn

[cobblerdave]

Re: opinions on techniques for dome waterproofingr

G'day
Have much the same conditions here at times .... When it rains it really rains.
With all you have done the entrance to your oven is an important spot to protect. The rain blows in there and its straight down those entrance hearth bricks and straight to your insulation layer. Capillary action really sucks.
So a water proof entrance door is a must.
The brickwork with naturally absorb water from the air so its not a bad idea to install a capable vent through your render to the insulation layer to aid any water to exit. I have a one inch brass pipe fitting with a screw down cap, its small and hard to spot and does the job.
Hope something here helps
Regards dave

[Gulf]

Re: opinions on techniques for dome waterproofingr

Hey Merlyn,

Some great advice from my good friend Dave. I very much like that you want to preserve the "perfect look" of the pompeii . I would just like to add:
Do apply a water proof barrier between your structural slab and your floor insulation.
Don't skip the vent if you plan to totally waterproof the masonry shell of the dome from the elements.
Do skip the interior water barrier, that you described. (Any sealing from the elements will need to be done on the outermost shell).
Do skip the foil (same logic).

That being said, I went with an A-frame roof over my oven. It covers the oven (and me) in wet weather. But, I can still "show of" her "perfect" shape

I get over to Fort Morgan and Gulf Shores a few times a year. I rescued a couple of "condo owner" friends of mine with some very needed repairs and improvements. So, I get free condo rental as a perk. I would love to stop by sometime and check on your progress, If you would like.

[merlyn]

Re: opinions on techniques for dome waterproofingr

D
Thanks I`m going to start the project next week . I have all the materials and I want to get all my ducks in a row as well . Vent never thought of it I suppose a couple of copper tubes one on each side from the fiber layer out should do it . Water proof layer on the concrete great idea . I`ll put on a couple of coats of the pool paint .would that be good enough?
Question ?? why not add the water proof layers as well on the inside just in case ? over engineer it > I plan to use a sealant on outside as well . As for a frame roof it is one more thing for the next hurricane to take off ..
As for the door way , I will use a entrance way of at least 1 course of bricks in front of the dome . Maybe 2 . I will have a stainless steel door for the oven , and another door for the entrance.
Hey would be happy to see you ,,,I`m on the road a lot in the summer and fall ,But if we are around I`m not far from foley . Laugh when you can life is to short to be anything but happy !!!

[kanoer54]

Re: opinions on techniques for dome waterproofingr

Merlyn,
Listen to Gulf. I learned a LOT from him...(my mentor). He is from your part of the country and can give you great advice.
jon

[Tscarborough]

Re: opinions on techniques for dome waterproofingr

The bottom line on a non-roofed oven is that you will get water intrusion, period. Plan for that: vent it as stated, and flash it at all intrusions (base, chimney, etc), and provide for an outer door as well as an inner one.

[david s]

Re: opinions on techniques for dome waterproofingr

Skip the foil. I tried this with my oven and now wish I hadn't. Fortunately I perforated the foil in two places, at the top and about two thirds up from the bottom. Each had an area of around 8 square inches. Moisture condenses on the inside of the foil then runs down to the base of the dome, making it difficult to find its way out the vent, which in my case is located around the support for the flue pipe. I know this because the two perforated patches are the only places where the steam exits. The exterior of the dome gets considerably hotter there as it is being heated internally by the escaping steam. It gets so hot that i can't hold my hand there for too long while the rest of the dome is not so hot. When the oven is dry the exterior is barely warm. Foil in this area may help any water intrusion and provide some extra insulation, but it also does a really good job of keeping water in. You are better off drying the oven as thoroughly as possible, which takes around three times the time and lots more fuel than you would think, then waterproofing the exterior.
By all means go ahead with your foil idea, but I think you'll regret it.

[merlyn]

Re: opinions on techniques for dome waterproofingr

Ok good to know , no foil no interior water barrier.. Now of course the next question is what about my water proof coating on the top . that won`t let steam escape either . Also I read about marble dust mixed with the last layer of portland . . How about granite dust lot of counter top places here I would be able to get that easy . Thought for the vent on the base I would use copper pipe and do 2 one on each side from the ceramic mat layer out to a hole in the slab.

[cobblerdave]

Re: opinions on techniques for dome waterproofingr

G'day
Heat and steam tend to go up that's why I placed mine at the top of the oven dome
Regards dave

[Gulf]

Re: opinions on techniques for dome waterproofingr

Thank's Jon,
Wow!.........for the compliment. I have many "mentors", as I am sure that you did, also.

............ Vent never thought of it I suppose a couple of copper tubes one on each side from the fiber layer out should do it ....

I think of a vent as means for steam to escape at the very apex of the dome. That is what CobblerDave is referring to. It should be designed to let vapor out but, not let water back in. If you are talking about drains at the base that is not a bad idea either. But, along with drains, I think that the best way is like many have done. That is, pour your hearth slab with a slope to the outside. Your hearth slab should slope from the very center of the dome outward in all directions. Like TScarborough said "..water intrusion...plan for it".

....Water proof layer on the concrete great idea . I`ll put on a couple of coats of the pool paint .would that be good enough?

I think that the pool paint would be fine between the hearth slab and the insulation layer. That, a sheet of plastic, a scrap piece of vynil floor covering, etc. Anything would be better than what I did which was nothing. I did not do as great of research as I should have.


Question ?? why not add the water proof layers as well on the inside just in case ? over engineer it >

Each layer that is "water proofed" (there is no such thing in the very humid area that we live) is just another layer that will trap mosture in. That is why David S, and I believe others advise against foil. The radiant heat that you think will be turned back in will be offset by the moisture that it traps. UtahBeehiver (Russell) did this, but he poked about a zillion holes in his before he covered it up. That may be the best way, if you think that you really need the foil.

I plan to use a sealant on outside as well .

Great!


As for a frame roof it is one more thing for the next hurricane to take off ..

I can relate to that! I got very tired of the taiste of charcoal in the weeks after Katrina. That is what utimately led me to WFOs and this forum .


As for the door way , I will use a entrance way of at least 1 course of bricks in front of the dome . Maybe 2 .

Many will tell you that the "short reach" of of one is enough to make the oven "easy" to work. They may be right. I don't know from experince but, I like the idea of 1 and a half. It gives a reasonable reach and allows enough room to "easily" install a flu transition. Two is over kill unless you plan to be cooking during a hurricane

..........Hey would be happy to see you ,,,I`m on the road a lot in the summer and fall ,But if we are around I`m not far from foley.

Foley (the outlet malls) is the only thing that I hate about going to Gulf Shores. Any thing that we save on condo rental is many times over "eaten up" by my wifes "SAVINGS" at the malls there ......

[pikemonkey]

Re: opinions on techniques for dome waterproofingr

Hi, I'm in the process of my first oven build right now. Monolithic cast refractory (1400C) dome. Casting tomorrow if today goes to plan.!!!
Done loads of research and got some great info from this forum. Now the foil comments have given me something to ponder.
For the floor I am putting 3" firebricks onto a 3" thick Calsil. Levelling the bricks down with a fireclay/sand paste onto the Calsil.
I have been advised to cover the Calsil board in aluminium foil to prevent it absorbing the moisture from the clay paste.
I have also been advised to foil over the dome insulation blanket (foil under chicken wire) to avoid sucking moisture from the final render.
Seemed like sound advice, but what do you guys think?
I have already prelaid 2" of vermicrete onto the stand, so I was going to completely wrap the Calsil board in foil.

[cobblerdave]

Re: opinions on techniques for dome waterproofingr

G'day
A bit of moisture from the clay paste is not a problem at all. It's the fact that the dry insulation sucks the moisture from the paste making it bloody hard to use a notched trowel to get a leveling surface that's the real issue.
I just used a smear of table margarine on the insulation stops this and keeps the paste workable so you can get on with the important task of getting a level hearth floor.
Your ovens an organic beast. Moisture is part of it. Your wood will contain 20 per cent moisture anyway, were do you think that ends up?
The trick is to stop large amounts rain etc from getting in. But the stuff that you get naturally from the air and wood must be able to get out as well. Forget the aluminium
Regards Dave

PS the oven sounds cool ... How about some build pics

[pikemonkey]

Re: opinions on techniques for dome waterproofingr

Thanks Dave. Build pics will follow.
If the Calsil absorbs water, will it swell and offset my firebricks?
What about ambient moisture/rain getting at the entrance and wicking into the oven floor?
Had another chat with supplier this morning - they say encase the Calsil board completely in foil and put the fire bricks down loose without the fireclay?

Cooking dome will be a one piece casting, 40" internal, 4"thick, cast on a form of sand covered with wet newspaper. And some wooden arch forms.

The flue arch will be cast separately. This to give the option of different positioning.

I'm torn between different schools of thought:-
To provide a thermal break or not between dome and flue arch??
I've seen David S mentions Vermicrete insulation here. Since I'm going to so much trouble and expense for thermal mass and good casing insulation, I want to retain as much heat for as long as possible in UK weather.

I like this idea, but with a minimum recommended castable thickness of 2" and approx 1" of insulation, I'm looking at the flue being 3" away from the cooking dome entrance. Also the flue needs to get hot for a good draw.
Would this distance and insulation affect the draw??
Going for an 8" flue.

[boerwarrior]

Re: opinions on techniques for dome waterproofingr

pikemonkey

I and several others on this forum used nothing at all between our CalSil insulation and the floor fire bricks. If your CalSil is level and your bricks are close to the same size then "leveling paste" is unnecessary. Remember that there is not such thing as 'perfect' (well, except for Les!) in a brick oven anyway.

If you do need some leveling you can use dry brick dust. Once you start using your oven the ash gets down between the bricks and kind of locks everything into place anyway.

You asked a lot of questions in one post!

Good luck!
Neil

[pikemonkey]

Re: opinions on techniques for dome waterproofingr

Thanks boerwarrior.
All noted thanks.

Yup - asking a lot of Qs, and condensing them into one post, since they're the only ones I have right now.

Just trimmed some Calsil up so will try an offcut in water and see what happens to it.
Since we have a fair bit of wet weather in the uk, I want to make especially sure the oven floor doesn't fail. I do like to over engineer!!!

I have laid foil under the Calsil, but reckon I will take your comments on board and place bricks loose on top, without foil here. See how flat it all is.