Building a house with concrete blocks

Glue. Seriously. We used minimally expanding foam. Comes in a can. It is extremely sticky. We used that to draw on the wall and then pushed the pink foam up against the block walls hard using 2x4's to brace it. Then repeat for the next layer of pink foam overlapping the joints. This produces a great insulation seal. Next we parged the entire exterior of the pink with a PVA fiber sand based concrete. To get it to stick to the foam let the foam age in the sun a little, scratch it up and paint it with a neat cement. Then parge from the bottom up. Works slick. Next draw texture the concrete with stones by dabbling and then lines to produce fake rocks. From a little distance it looks like a stone cottage. Someday I'll do the outer stone wall with real field stone. Project for another year.

On the poured wall along the uphill side and half the front the foam never came off from where I did the pour. Twenty years ago I figured out to line my concrete forms with foam when pouring to get a great bond and easy release for the forms. That side had a poured knee wall because there will be more hydrostatic pressure there so it is poured as one piece with the slab.

Cheers

-Walter
Sugar Mountain Farm
in the mountains of Vermont
http://SugarMtnFarm.com/blog/
http://HollyGraphicArt.com/
http://NoNAIS.org

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SugarMtnFarm.com -- Pastured Pigs, Poultry, Sheep, Dogs and Kids

Wow, thanks Walter, I'da never thunk to use the foam, but you're right it IS very sticky!
Did you tryto completely coat the wall with it, or just spray "lines" of foam? I'm thinking that trying to smooth lines of foam over the whole wall would not work so well, as the foam kind of disintegrates when you touch it...and I guess pushing the foam board hard against the wall would spread out the spray foam alot anyway?

Thanks much!

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You can't ride, til you get on....

Hi Guys,
What did you do for the floor my original plan was to pour concrete over reinforceing mesh with pex radiant heat tubbing in it. How thick did you pour if you used concrete?
I'm planning on 4 inch on dry sand over 2 inchs of foam on the perimeter. providing heated water using a tankless water heater with a solar pannel or two down the road if I can swing it.
The expanding foam idea for glueing the foam together is brilliant I was hopping to find the long steel fasteners but they go thru to the cement block so that would hole the water tightness. I plan on berming it to two feet of the top of the wall and putting a more or less conventional roof with a standing seam roof. how expensive was the dome to build?
So your idea of making it look like stone is great one also.
Dutch

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SW Minnesota
Been a fool most of my life and still help as best I can:
knowing no good deed ever goes unpunished.

Hi Dutch, when we build we also want pex radiant floor heat, but I don't like the idea of it embedded in concrete. I want to be able to fix future problems. So we are planning a brick on sand floor, with sand in the cracks, like you do on a patio, and then seal the whole thing with a clear sealant. That way we can dig out a portion if needed for repairs, then reseal...

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You can't ride, til you get on....

4" of slab is good. If there will be interior weight bearing partitions consider making those spots and about 1' wider on each side 6" or even 8" depending on the load. You can do the math or just do overkill.

Don't put long metal fasteners through the foam. I experimented with that years ago. The heat conducts right through and they become a path for water, bugs, etc.

We did the dome ourselves, actually a barrel vault rather than a dome. The total cost of the cottage is less than $7,000 everything included and the barrel vault is just a small portion - maybe $1,000 absolute max. Labor not included of course since we did everything. See this search patter for discussion of the roof construction.

http://www.google.com/search?&q=site%3Asugarmtnfarm.com+tiny+cottage+roof
PEX / in-floor radian heat is something I want to try but have not played with yet. My brother did it under the wooden floor of his bathroom and then insulated under that. He likes it a lot. I've spoke with other people who have done it and all liked it including one 90 year old relative of my wife who's husband put it into their house back in the 1950's. Not PEX then but same idea and it still works great.

Like bbbuddy says, my one fear is something going wrong with the pipes embedded in the concrete and not being able to fix them. My first test, which I'm working on now, is in sand in the bathroom. Rather than PEX it is PVC and doing heat recovery from the bathtub. A first test of ideas.

Cheers,

-Walter
Sugar Mountain Farm
in the mountains of Vermont
http://SugarMtnFarm.com/blog/
http://HollyGraphicArt.com/
http://NoNAIS.org

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SugarMtnFarm.com -- Pastured Pigs, Poultry, Sheep, Dogs and Kids

You can build a fine home using block. Take a look at some older block buildings and look at the corners. Look for cracks. It's not unusual to see a crack running along the joints in a stair step pattern where the foundation under the corner has settled.

Make sure that for your soil condition you have a wide and thick enough footer.You're going to be putting a lot of weight on them. I'd use a number 6 or 8 rebar in the bottom. Buy the 2" cement spacers to support the rebar in the trench. Overlap the rebar and tie it based on the size you use. I'd space the rebar about 3" to 4" across the bottom of the trench. Make sure the rebar is at least 2" from any surface. If you're buying concrete go for somewheres around a 4" slump. Rule of thumb: one gal of water per yard equals a 1" change in slump. In general the more water the less ultimate strength you'll end up with.

To strengthen the block walls to resist high winds use the horizontal reinforcement and incorporate a bond beam at the top with two bars running the circumference. They make a block shape that looks like a trough for the bond beams. fill the trough with grout (sand, water and cement) after you have the rebar in place. If you add vertical rebar into the footer you can continue the rebar all the way up to the bond beam. The vertical rebar can be about every four feet or so. You'll want to grout those cells too. You don't have to tie the vertical rebar. Simply stuff a bar into the wet grout so there's an overlap with the bar below.

For insulation you can get the same two part foam (Handi-foam is one brand) that insulators use. Drill a small hole at the bottom of an empty cell and foam the cavity until it comes out the top.

You'll have a stronger, better insulated home than most. Good luck!

No.. I detest drywall...we are currently drywalling a 3000 sq ft house and the work is aggravating, unforgiving, and Yuk...i just hate it... but you are right the $$'s made the decision.

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Christanie Farm...living life as it was intended

Good points but I would strongly suggest not filling the concrete block cavities with foam. It is a waste of money and insulation. The energy will be transmitted through the connection points of the block, the bars of the H. I've done tests on this. It isn't worth it.

Instead, insulate outside the block wall. That way you gain the thermal mass of the block wall inside the house to keep you warm in the winter and cool in the summer. It acts as a flywheel. For this same reason the Insulating Concrete Forms (ICF) are not a very good idea.

The #6 or #8 rebar is way over kill and expensive as well as being hard to get in some places. #3 is strong enough, #4 is what we have readily available here, a little stronger and what we used. Putting in the bond beams at the window sill and top of the wall heights with one pieces of rebar in addition to one piece in the foundation beam (we used floating slab) makes it far stronger than putting in extra rebar in the foundation. This is because the whole house becomes a beam with a ring beam at the top and the bottom since they go all the way around - the window sill height gets interrupted by the door(s).

A very important issue is to understand your soils and put the house firmly on hard packed soil - or ledge. You don't want one side of the house settling!

Cheers

-Walter
Sugar Mountain Farm
in the mountains of Vermont
http://SugarMtnFarm.com/blog/
http://HollyGraphicArt.com/
http://NoNAIS.org

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SugarMtnFarm.com -- Pastured Pigs, Poultry, Sheep, Dogs and Kids

You have some good points. The heavier rebar will be hard to find. In this area finding anything over a #4 is tough. FWIW, the one story block building I'm working on that was designed by an architect used #8s in the footers. There's no doubt the foundation was designed for worse case. That was the owner's decision.

We had some 2" thick foam panels that came in 6' by 6' sheets. They were used to insulate the foundations and used for the first 2' next to the footers under the slab. The foam didn't meet some of the requirements when subjected to flame. There's a strict restriction on using it anywhere above grade after the architect found out it didn't meet spec.

I don't think using foam on the outside of a block wall would be a problem. I would be very careful about using it in the interior of the house unless it was the type that wouldn't add an additional hazard during a fire.

Totally agreed on the foam. Keep it all outside the house. That achieves both the thermal mass inside the insulated envelope goal and fire safety. This is a big factor in our design, we have as little burnable material, including possessions, as possible inside the house.

2"x6'x6' sheets of foam, that's a size I've never heard of. What was it? Was it closed cell?

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SugarMtnFarm.com -- Pastured Pigs, Poultry, Sheep, Dogs and Kids

They used 2" Foamular 250. I was wrong on the sheet size. That's probably why you haven't heard about it. http://www.owenscorning.com/around/i...s/foamular.asp