AAC Blocks

[Brian_Weekley]

I've been reading with great interest Canopy's "In-fill" thread.  Not because I'm interested in an in-fill application, but because it got me to do some reading on AAC blocks.  Instead of hijacking Canopy's discussion, thought I'd start a new thread specifically on AAC blocks.

Down the road, I'd like to build a TF home.  However, I've constantly struggled with how I would finish the timber frame envelope.  I want it to be very energy efficient and "green".  Hay bale looks way to difficult and I'm not real keen on SIPS.  However, the AAC blocks look like a very interesting alternative.  They also seem to have some nice advantages like resistance to pests, long lasting, good energy efficiency, and easy to work with.

The problem is I can't seem to find a lot of pictures and examples for residential use.  For a house in Maine, I don't want a block or stucco look.  I've read you can put other types of siding on it.  Question to the forum:  have any of you actually used this product for a timber frame?  Has anyone applied a traditional type of siding on the exterior?  I'd really like to see some pictures and feedback from those who have used it for a timber frame application.  What are the cons?

[Jim_Rogers]

Have you found any pictures on the manufacturers website?

I would think that a salesman for a company that produces them would be able to supply some information about their product.

I have not heard of these before Canopy brought them up.

Jim Rogers

[Thehardway]

Brian,

Although I have not used them specifically in a TF structure, I have built with them.  I built a small 16 X 20 Shed roof building to serve as a transmitter building for a radio TV station.  We chose AAC because it offered everything we needed,  Thermal performance, fire resistance, modular and easy to transport and assemble the top of the mountain, one piece wall assembly. 

AAC block is really cool stuff.  To work with it, you need to throw out any notions you have of it being like a lightweight concrete block.  It is much different. 

AAC can be made to look like a variety of finishes on the exterior. Using a few special or homemade tools you can groove the outside and easily make it look like traditional brick. If you chip around the edges of each block it is quite easy to make them look like split face stone, if you want to apply a siding over it, it is easy to attach wood or vinyl siding just by using coarse thread drywall screws.  They will screw right into it with a impact driver, no need to predrill,  and they will not pull out, although it is not advisable to try and remove and re-use the same hole. 

You do not put them together with regular mortar.  A thin-set type compound  called "thin bed mortar" is used and spread on with a grooved trowel.  Mortar joints are almost invisible.  It can be cut and carved with just about any edged tool. 

You should have no problem at all putting siding (external finish) or sheetrock (internal finish) on this product and you would not need any type of furring strips to do so unless you wanted to ventilate the back side of your siding for some reason.   

An 8" thick block gives you a wall that is fire rated for 4 hours and has the thermal performance of a 6"  R-19 conventional stud and batt wall.

So what are the downsides?
1. A little more challenging in the planning stages as to where you want to put all your receptacles and how to run you wires.  (similar to planning a SIP or Log home envelope).
2. It is hard on your hands during assembly (where some comfortable gloves)
3. It is dusty (where a dust mask and have a shower handy at the end of the day)
4. Inspectors are not familiar with it and may give you a hard time about a viriety of things like structural stability, reinforcement points, lintels, insulation, etc.  Fortunately you can point them to engineering documents from the manufacturer for most of this.
5. It can be expensive to have it trucked to your location as there are only a few manufacturing sites in the world.


The plant nearest to us was in Georgia so it wasn't too bad but for some folks the shipping could be cost prohibitive, especially in remote areas.

Some things you may not know about it are it comes in many different shapes, sizes and forms and can be used for an entire building envelope including roof and floor decks.  It comes in planks that can be stood up vertically  (might be a neat way to do a TF enclosure).
It is nearly indestructable by fire, wind, and impact.  It is very dimensionally stable. It is very energy efficient and "green" using less materials and providing superior performance to CMU products although the autoclaving part does require significant energy input during manufacture.

Hope this helps, I would be happy to answer more specific questions.  There are some great videos on YouTube about it and you will find it more common in European building forums than in North American.  A lot is used in Germany and scandinavian / norwegian countries from what I could gather. TW might have some insight on it being used over there.

[Brian_Weekley]

Thanks, Hardway.

I saw that the only current US manufacturers are located in the south (e.g., FL, GA, TX) so shipping might be expensive.  I haven't looked into if any have local distributors in the NE.  Being able to install furring strips to the exterior that would allow installation of traditional siding would be great.  I also envision, that I could then add an interior wall (infill between posts) to run electrical, utilities, and attach the interior finish (e.g., drywall or wood).  This could also house additional insulation (e.g, spray foam or batts).  It is an intriguing system, but I'll certainly need to do more research.

One thing I always struggle to justify:  SIPS alone don't need a timber frame for support.  Likewise, I imagine an AAC block wall doesn't really need a timber frame for support.  Then we talk about maybe adding a stud wall in-filled between the posts...they all seem like redundant systems.  Obviously, we want the timber frame because it's a thing of beauty, but it sometimes feels like we're almost building two houses in one.  A barn is one thing, but for a well insulated house, do we actually end up using more resources for a timber frame?  Just curious.

Brian

[bigshow]

@Brian

as one who built a timberframe from start to finish.  I would say 'yes' - Most Timberframes pretty much boil down to framing the house twice.  Timberframes are a luxury.  someone has to say it.  I could go on, and on, and on, and on about the downsides.

I am assuming most on this board are everyday joes, and some of us are just figuring out how to make a timberframe in our lives practical, and thats awesome.  There is just something about them. 

Yeah, I think I've built an incredibly energy efficient and really awesome house.  Put a traditional contractor against me, sure he/she could probably trump mine for sure using traditional means - as long as they had mine as a benchmark.  that being said, I love timberframes and everything about them.   

anyways, about those AAC Blocks .

[witterbound]

I agree that timber frames are mostly redundent, except for the roof (where the timber frame provides the framing that replaces the trusses or other framing that would be needed up there), and some of the interior walls and beams that would be needed to support the roof/upper floor.