#1  
Old 06-18-2008, 10:31 AM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 780
Default Expansion question... is it a problem?

Hi all,
I have my wall stacked and thought I was ready to infill the cores. Now I think not. Here's the question: The plans do not have any rebar connecting the walls and the slab supporting the hearth. I expect this is due to an allowance for expansion of the slab as it heats. It seems to me this is not an issue as several people have finished their WFO with stucco and none have reported cracking along this join line.

Has anyone experienced any movement between the walls and the slab?

MY concern is that I live in an earthquake designated area. And here I'm building this WFO on a slab (the total of which will weigh several hundred pounds) and it won't be tied to the support base. I'm expecting some will say this is a non-issue as the oven itself won't be tied to the slab and if it wants to move then it will part company there. This may be true. I have some ideas on addressing that issue but right now I would like to know if anyone has had movement between the slab and the walls. Many thanks in advance.

Oh and yes, I have looked at Alan Scott's plans. He addresses the expansion due to heat issue by supporting the WFO on rebar pegs that stick out from the support slab into the surrounding support walls. He has an air gap and no connection other than gravity. Any sizeable movement during an earthquake and I suspect the oven is out thru the wall (IMHO).

Again many thanks,
Wiley
Reply With Quote
  #2  
Old 06-18-2008, 11:29 AM
Frances's Avatar
Il Pizzaiolo
 
Join Date: Aug 2007
Location: Allschwil, Switzerland
Posts: 2,186
Default Re: Expansion question... is it a problem?

Expansion shouldn't be an issue, because you'll have plenty of insulation between the slab and the oven... if the hearth slab starts getting hot enough to expand you'll have got something seriously wrong!

I think Alan Scott's oven has no insulation underneath, which would explain the difference. Doesn't it?

Earthquakes... dunno. ButI thought one of the issues with earthquake proof building that you make it flexible rather than fixed... so it will go with the sway rather than breaking up.

But I haven't had any movement between the slab and the walls.
__________________
"Building a Brick oven is the most fun anyone can have by themselves." (Terry Pratchett... slightly amended)


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #3  
Old 06-18-2008, 11:45 AM
asudavew's Avatar
Il Pizzaiolo
 
Join Date: Jul 2007
Location: san angelo, texas
Posts: 1,877
Default Re: Expansion question... is it a problem?

I'm not sure if I follow you.

But, if you are talking about running rebar up through the cells and tying them in with rebar in the hearth slab.. You will find that most builders do exactly that.

Here is a picture of mine, notice the bent rebar exiting from the filled cell.

As for heating the hearth slab... Frances is right.

Also, there is no sense in wasting firewood and time heating the hearth slab up. That's why the insulating layer goes on top.

Also , your oven will weigh a few tons.... not a few hundred pounds. So plan accordingly.

Hope this helps.

Dave
Attached Thumbnails
Expansion question... is it a problem?-rebar.jpg  
__________________
My thread:

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

My costs:

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

My pics:

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #4  
Old 06-18-2008, 12:32 PM
DrakeRemoray's Avatar
Il Pizzaiolo
 
Join Date: Mar 2006
Location: Littleton, CO
Posts: 1,211
Default Re: Expansion question... is it a problem?

I did not connect my slab to the walls, thinking about the expansion issue...no earthquakes in Denver...at least not frequent ones...looking it up, it appears we are due

BUT I think Alan Scott's book does mention tying the slab into the walls in earthquake prone areas.

I think I would go ahead and put some rebar up into the slab.

Drake
Reply With Quote
  #5  
Old 06-18-2008, 12:44 PM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 780
Default Re: Expansion question... is it a problem?

Frances and Dave, thanks for responding. I agree and thought I would ask because in the directions the drawings only have the rebar only in the cells and there is no reference to tying the slab to the support walls.

Regarding the expansion: I don't remember the exact post but it was mentioned by someone that their slab only got warm after many hours of firing. That seemed reasonable to me, I am a strong believer in insulation.

Also, Due to my wanting to have my stand in an "H" pattern I have a problem with dry stacking. The problem is that I cannot stack them in any way that does not have three breaks (ends of blocks butting) vertically in some location. With dry stacking any place where two blocks butt is the same as a crack in a wall, to have three in a vertical line (on a four block high wall) is basically a broken wall. I am going to unstack and restack gluing the blocks together with construction adhesive designed for such. I have done this in the past with the stackable garden wall blocks where we wanted the wall to be vertical not stepped back like they are designed. We broke of the lip on the bottom so they would stack vertically and in over five years have had no problems. We even tried to undo a section to make a modification and gave up-- that glue really holds. Odd the things we learn and then forget.

Frances, you are right about wanting limber and flexible construction in earthquake country. Part of my youth was in California near Loma Prieta, where that large quake was back in 1989. My parents still lived there at the time of the quake. At the same time, my wife and I were were just starting construction of our home. After viewing what did and didn't hold up in that quake we redesigned significant portions of our home. That being said, cement block and flexible are (I think) mutually exclusive terms :-) So for this construction I can only make it as strong as I can.

Wiley
Reply With Quote
  #6  
Old 06-18-2008, 02:55 PM
egalecki's Avatar
Il Pizzaiolo
 
Join Date: Mar 2008
Location: Virginia
Posts: 1,049
Default Re: Expansion question... is it a problem?

I have rebar fixing my block walls to the base slab, and I have rebar tying my hearth slab to my walls. Sort of like pegs sticking up out of the block cores and into, but not through, the hearth. We used the hammer drill to make the holes in the base slab for the rebar to fit in before we filled the cores.

Not much in the way of earthquakes here in SW Va, but we didn't want it going anywhere anyway...
__________________
Elizabeth


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #7  
Old 06-18-2008, 05:07 PM
Dino_Pizza's Avatar
Il Pizzaiolo
 
Join Date: Feb 2008
Location: Northridge, CA
Posts: 1,017
Default Re: Expansion question... is it a problem?

Hi Wiley,
I live in Northridge and lived thru a big quake and watched every foot of concrete block wall around my home crumble to the base. Nice way to meet your rear-yard neighbors! But, like the Pompeii plans show, filling every other cell with concrete and rebar does the trick. It's how Los Angeles changed the codes for all concrete block construction and it will hold up very well.
HOWEVER, I'm glad you brought the subject up cuz if you were worried about the stand, I've been sweatin' bullets every time a post says you build the heavy brick oven and it just sits on the insulation board leveled with brick dust and it doesn't move! I do believe them (I've yet to build mine) and they are experts in my mind but when I build mine I'm thinking of:
1. Side support or putting an angle iron against the arch wall and tap-cons into the oven floor (with a piece of insulation) like Ken524 did in "Vent & Chimney" photos about page 8.
2. Spread a 1/2" of high heat mortar over the brick dome. This adds mass (which I don't really want) but I hope it adds some strength too.
3. Do the heavy chicken wire over insulating blankets over the dome and again, attach it to something popping out of the oven floor slab.
Again, having not built one I'm ready to find out how silly I'm being. Besides, an earthquake catastrophe would you give you a change to rebuild it with all those little things you've learned along the way for an even better oven.
Enjoy the process,
Dean
__________________
"Life is a banquet and most poor sons-of-bitches are starving to death." -Auntie Mame

View My Picasa Web Album UPDATED oct

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


My Oven Costs Spreadsheet

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


My Oven Thread

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #8  
Old 06-18-2008, 05:29 PM
asudavew's Avatar
Il Pizzaiolo
 
Join Date: Jul 2007
Location: san angelo, texas
Posts: 1,877
Default Re: Expansion question... is it a problem?

Quote:
Originally Posted by Dino_Pizza View Post
2. Spread a 1/2" of high heat mortar over the brick dome. This adds mass (which I don't really want) but I hope it adds some strength too.
Hi Dean,

I've been thinking about a mobile oven, where shaking and bouncing would be a problem.
I would do the same, but why not add a nice fine wire mesh (small hole chicken wire) to the 1/2 inch of mortar. I think that would help to. It would be like rebar in concrete.


just a thought,

dave
__________________
My thread:

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

My costs:

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

My pics:

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #9  
Old 06-18-2008, 06:13 PM
mfiore's Avatar
Master Builder
 
Join Date: Oct 2007
Location: Michigan
Posts: 919
Default Re: Expansion question... is it a problem?

Quote:
Originally Posted by Wiley View Post
Also, Due to my wanting to have my stand in an "H" pattern I have a problem with dry stacking. The problem is that I cannot stack them in any way that does not have three breaks (ends of blocks butting) vertically in some location. With dry stacking any place where two blocks butt is the same as a crack in a wall, to have three in a vertical line (on a four block high wall) is basically a broken wall.

Wiley
I am also building an "H" pattern hearth stand. I've encountered the same dilemna, how to tie in the middle bar with only four courses of block. I went as far as using my son's legos (they actually work pretty well, and are much lighter than concrete) to try different approaches. In the end, I'm not sure it matters. There are ovens with support only on the sides, open from both ends in the middle. I think the middle part will be a free standing wall, holding up the concrete slab. Does it need to be tied into the rest?
__________________
Mike - Saginaw, MI


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #10  
Old 06-18-2008, 07:09 PM
christo's Avatar
Master Builder
 
Join Date: Feb 2006
Location: Eastern NC
Posts: 910
Default Re: Expansion question... is it a problem?

I have a center wall in my block base and did not tie it in to the rest of the base, per se.... The hearth pour tied into the wall only.

I used fiber reinforced wall bonding cement to coat my entire base - inside and out. I have no cracks on the inner wall and it has been about 9 months since I coated.

I plan to finish stucco a little later this summer.... too much to do at work.

Christo
__________________
My oven progress -

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
4 courses up... and a big question Throw Deep Newbie Forum 35 03-31-2008 01:54 PM
Thermal expansion in floor/vent landing design jschwappach Getting Started 4 01-16-2008 08:12 PM
Thermal Expansion Question - Dome vs Hearth Kemo Pompeii Oven Construction 14 10-03-2007 01:18 PM
Pouring Hearth Question telehort Getting Started 7 01-29-2007 10:20 AM
Construction of Chimney question dmun Design Styles, Chimneys and Finish 0 07-18-2005 09:08 AM


All times are GMT -7. The time now is 07:45 AM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC