Weep hole and FB board placement

[mnagy]

Here’s the planning for my next step… I’m gonna put one course of bricks around my concrete block stand flush with the poured reinforced concrete top. Then I’ll put a row of bricks on their side around the perimeter making a space for 4” of vermicrete. I’ll use some scrap tile between the concrete and vermicrete, and will make sure there are some 3/8” holes through the top slab for drainage. Anything else I should think about for this step? Thanks!

[david s]

A vermicrete slab is considerably cheaper than calcium silicate board. However it takes more labour to mix and place and the free water in the mix requires removal, preferably before laying the floor bricks over it which traps the moisture remaining in it. This problem is eliminated if a dry calcium silicate board is used, although it can suck up moisture at the same rate and quantity as a vermicrete slab will if it gets wet, so the weep holes are good insurance as underfloor moisture is the hardest to get rid of . I've had experience with the oven insulation building up moisture just from our tropical humidity even though there was no rain entry.

Any moisture left under the floor will travel in the opposite direction from the heat so the placement of the weep holes is probably not that important, but a decent pathway to them will facilitate exit. It is far easier to cast in the holes (I use some foam which is easily removed) when the supporting slab is laid than having to drill them once it's set. Dodging reo bar and the hole blowing out can therefore be easily avoided.

you might find the attached study on drying a vermicrete slab useful.

Vermicrete insulating slab PDF.pdf

[Gulf]

If I just use 4” of vermicrete/peri Crete on the entire hearth, do I still need weep holes and/or tile underneath? Or is that just for this FB board?

In my honest opinion, yes. However, it does present some problems that I haven't seen tackled to my liking. On the Simmental Farm 36" we were going to do just that, but the owner found enough free CalSil to have 4.5" of floor insulation. Had we have used the vermicrete, we were going to place a layer of window screen wire on top of the mosaic tiles and then a thin layer of landscape fabric on top of that.Next, we were going to place a thin layer of 5 to 1 vermicrete (with as little water in the mix as we could get away with) in the form. After that set we were going to proceed with the rest of the pour still with as little as we could. That should have worked to keep the spaces, grooves and weep holes open.

[mnagy]

If I just use 4” of vermicrete/peri Crete on the entire hearth, do I still need weep holes and/or tile underneath? Or is that just for this FB board?

[MnDude45]

This is a very helpful thread. Thank you for sharing.

[Baza]

SableSprings Thank you! Yes - water is as necessary to life as it is insidious in a build! Thank you for the help and guidance here! I appreciate the support of the builders here to outline not only a problem but incentive and creative solutions! Off to get some tile!! (Just dug my first foot of foundation hole - 3’ more to go - damn frost line!!)

[SableSprings]

Regarding the placement and order of layers for the oven, I've added two links below that had particularly good diagrams/pictures of the updated recommendations from the forum folks. The free forno bravo plans definitely are out of date in some respects. A lot of innovations have been developed by forum members and the plans are now simply give you a good overall view of some basic build types to consider with good background info. Remember that the original basic (ancient!) Roman & Tuscan designs are still valid...it's just that now we have much better materials and techniques that improve upon the original designs (insulation materials for example).

Hope the build links below are useful to your understanding of the current recommended "upgrades"...

https://community.fornobravo.com/for...andpoint-idaho

https://community.fornobravo.com/for...522#post411522

p.s. Water/moisture is a constant issue to all WFO owners. Even though you do everything absolutely correct, water seems to poke it's ugly head into the system somehow even when you build an outer structure to protect the oven from the elements...hence, including the screened weep hole, tile to lift the insulation board off the concrete hearth, and the addition of some sort of top insulation venting are best practices for building a WFO. One of those "Ounce of prevention is worth a pound of cure." issues.

[Baza]

UtahBeehiver is the KING!! Wow - thanks lads - excited for you plastered (great handle by the way!). And good luck on your next steps Chobbs! plastered thank you for the pics and explanation. I’m wondering if this is a step I have to do given I will be building an enclosure for my oven? Or is this just good practice no matter what the finish? Sorry the newbie questions!

[Chobbs]

plastered Thanks for the quick reply.

My order of CaSi board and bricks should be coming soon so will still some holes tonight and grab some tiles!

Thanks again.

[plastered]

Chobbs and Baza

I'll let others comment on my work, but I found a bunch of old tile in my basement, broke it up (it was like 12x12" so a little too big) and then scattered it about under the floor. Then I randomly drilled 4-5 holes through the slab. Then I cut up some old screen I found in my basement too, and draped it over the holes (to prevent bugs from getting in apparently). I just used the weight of the tile chunks to secure the screen in place.

I have arrows pointing to the dark spots where I put the screen and weep holes (sorry I didn't take a birds eye view). In the other pic, you can see where I laid out some other tile I found, but I didn't have enough of it. I think the recommendation on this forum is to get the mosaic tile sheets and lay those down. I wish I would have had a little more tile, mines a little spacious but I had already run to the hardware store several times and thought it would be fine as is.

[UtahBeehiver]

Weep holes provide a means for any water that gets in can get out otherwise it just sits there and may be absorbed by the CaSi board.

[Chobbs]

I’m in the same situation as Baza. I have downloaded the FB plans and just assumed that laying the CaSi board down and placing the floor tiles on top was the way to go.

Being in the UK there is always rain around the corner so should I look at putting weep holes into my concrete hearth or should I be putting something else under the CaSi board?

My dome will be outside the floor so the CaSi board is going to be as wide as my external diameter with an exposed igloo design I was just going to render over the CaSi board after the blanket is attached and Vcreted. Is this correct?

[Baza]

Ok - totally new to this and about to start my build! YIKES - terrifying to see so many mods to the Forno Bravo plans that they seem almost redundant! As I try to wrap my head around what to do for the floor of the oven I see this set of posts re: tiles and weep holes (neither mentioned in Forno Bravo design) - so what are they?! Are you putting tiles (what kind? size? configuration?) under the 2" fibre board? and are you drilling holes under the floor in the spots you noted to allow water to seep out?

I really need some advice here.

I have seen everything from just put the hearth down, 2" fibre board, then firebrick floor and build (Forno instructions) to 4" of percrete, then the FB and brick floor. Then this - with the tile (what kind?) and holes in the hearth for drainage .

Wow - I'm really confused - help!?

[UtahBeehiver]

Low spots if any otherwise water typically migrates from the outside of the dome in. No need to set tiles with thinset or mortar. These ovens are heavy.. Consider 1/2 soldier or 1/2 header for your first course to minimize outward force of dome.

[plastered]

Thanks, I knew what I had seen was fishy.

Any suggestions on where to place the weep holes? Also, should I apply some sort of adhesive between the tiles and the hearth (caulk/mortar?) or is the weight of the dome sufficient?