Continued Design Ideas

[Derkp]

Re: Continued Design Ideas

Craig,

Looks good, my slab is on about 6-7 inched of 1" rock and is 6" thick, I also have lots of rebar and 6" square mesh in the slab. It has not moved a bit.

The weather sure has been nice here, calm before a storm, probably.

Derk

[clofgreen]

Re: Continued Design Ideas

I can't see that drill lasting too much longer if you continue to use it as a grinder. Do yourself a favour and get a 4" angle grinder, they are an indispensable tool, you can cut or grind steel, concrete, wood, ceramics etc. using the appropriate discs. Keep your makita drill for drilling.

I see where you are coming from, right tool for the right job, but this is a circular sander, not a drill, and is basically the same engine as an angle grinder. The metal grinder wheel is a perfect fit so I don't think there will be too much problem. Besides, we're talking a very small amount of rebar that needs cutting.

[clofgreen]

Re: Continued Design Ideas

Craig,

The weather sure has been nice here, calm before a storm, probably.

Derk

Utah weather at its best! Took this off my deck just now:



Spent the morning pouring my slab. Never worked with concrete before. Actually was pretty easy. Here's a pic from my deck.



And a closeup.




Given the nice dry Utah fall weather, how often should I be spraying the slab? High today will be 63. Humidity is 35 - 40%. Winds are light. Should I cover it with some plastic?

[SCChris]

Re: Continued Design Ideas

Plastic is good. As I remember, the strength builds for the first 5 days or so, but you should be fine to start the stand in a week. Warmth is also a factor for proper curing.

Better info can be found here
http://en.wikipedia.org/wiki/Concrete#Curing


Chris

[clofgreen]

Re: Continued Design Ideas

Thanks for the advise and the link. I sprayed the concrete then covered it with plastic. I figure if I can see condensation on the plastic the moisture level should be OK. I read that spraying once a day is sufficient. Does anyone disagree? (I put soup cans over the rebar to keep from tearing the plastic.)

[Tscarborough]

Re: Continued Design Ideas

At 63 degrees and covered by plastic, once is probably fine. Not once a day, but once, period.

[clofgreen]

Re: Continued Design Ideas

Tscarborough,

You once wrote, "Normal construction practice is to begin laying structural CMU on 24 hour slabs." I poured my slab yesterday, finished at noon. Am I safe to start building my CMU wall tomorrow? I assume I should keep the slab wet at least for five days. Will keeping the slab wet ruin the mortar?

Craig

[Tscarborough]

Re: Continued Design Ideas

You can lay block on it anytime, and you do not need to keep the slab wet unless it is 90+ degrees and windy.

[clofgreen]

Re: Continued Design Ideas

I couldn't stand being shut up in an office with autumn in full bloom so took a week off and spent a good part of it on my WFO. Based on the wealth of wisdom so freely shared on this forum, I was able to get a lot done and think that it turned out fairly well. Here are a few pics showing progress and a few notes on lessons learned.

Here's the finished stand. Rebar has been grouted in corner blocks. Brick ties have been bent down to keep from putting another rip in my pants.



Half inch Hardibacker was easily scored with an $11 tool from HD. Holes were cut so that the rebar and concrete slab could tie into the grouted cores. I considered turning the metal angle up to act as part of the form but chose not to. I used a hammer and chisel to cut a notch for it to sit into.



Scrap wood from part of the deck I tore out were used to build the form. Since the wood was so dry and porous I ended up lining the form with plastic so that moisture wouldn't wick away from the concrete and so that the forms would be easy to pull. I built little wire rebar chairs from the excess foundation wire mesh.



The hearth pour was easier than the foundation pour after I found out that 3.5 quarts of water per Sakrete directions is so stiff you can hardly work with it. Adding just an extra cup of water made all the difference in the world. So what if it is 10% weaker.

[cynon767]

Re: Continued Design Ideas

Great progress, and looking really good. And just an extra cup of water won't hurt the concrete strength enough to cause problems. I like the hardiebacker beneath the upper slab as a leave-in base... if I were building over again, I would go this route.

[clofgreen]

Re: Continued Design Ideas

I pulled the forms and the hearth slab looks nice (left my camera at work. I'll post pics later).
EDIT: Its later, here's the pic.



Now it's time to think about insulation. I've read many posts about the value of insulation but am not sure I want to spend the $$ for all that Fiber Board. So here's my question:

Can I use a 4" 5:1 perlcrete slab where the heavy loads are and go with, say, a 10:1 mix where the loads are light, like under the floor? It seems to me that putting the 10:1 under the floor where it is hottest and not very heavy would be a good idea.



Similar question: If I put 10" or so of perlite over the dome can I get by without the fiber blanket?

Thanks for your help.

Craig

[Tscarborough]

Re: Continued Design Ideas

Compromise to make it easy and use 8-1 under all. Also no need for blankets if you use perlite over the top.

[clofgreen]

Re: Continued Design Ideas

I've built the forms for a 6 inch perlcrete hearth pour and am planning to use an 8:1 mix as Tom mentioned. But it is getting cold here in Utah, highs in the 40s, lows 28 to 30. I read that the temperature shouldn't go below 50 for the first five days so that the cement will hydrate properly. Would a heat lamp under a plastic tarp be sufficient or do I need to do something different?

Craig

[SCChris]

Re: Continued Design Ideas

In Snowbird you must be getting some below freezing nights.. I'd expect that a lamp might be enough. Can you tent the whole structure?

Chris

[clofgreen]

Re: Continued Design Ideas

Actually, I'm not in Snowbird, I'm 12 minutes and 3500 vertical feet away (that road really climbs). But yes, we are getting below freezing quite often. Was 23 several nights ago.

I thought I might build a simple wood frame to support the tarp and hang the heat lamp from it. Just wasn't sure if a tarp was sufficient to keep the heat in or not.