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Is an infill wall practical?

Started by canopy, February 28, 2012, 08:49:40 PM

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canopy

I am debating an infill wall system versus making the walls flush on the outside of the posts. See picture of wall at corner post. The benefit of the infill wall system is it shows the joinery on the outside (posts, braces, plates). But the downside is I am guessing it will be necessary to have expansion joints between wall and timbers so there are no gaps as everything shrinks and swells with the seasons. I see the infill look on many old structures in Europe so wonder how they coped with this? I am leaning towards an AAC block wall.



shelbycharger400

i have read about similars,  constant maintence when wood meets the concrete,  over years,  lots and lots of caulking!!

TW

European infills were originally lath and daub. That is a mesh of thin withies and coverd with clay based mortar. Then they switched over to brick infills built with lime mortar.

I have absulutely no own experience of this technique but I have read and heard that the sill was rather prone to rot and had to be made from the best heartwood oak timber you could find. I have also heard that if you use any cement at all in the infills the frame will rot while you stand back and look at it. Cement mortar is more rigid than clay or lime mortar and will therefore crack. Water seeps into the cracks and destroys the frame. I do not know if this statement is true but it makes sence to me.

Jim_Rogers

A while ago, another asked about having an infill system that allowed the frame to be seen from the outside as well as from the inside.

Here is a link to that thread:

https://forestryforum.com/board/index.php/topic,55893.0.html

If you go to the site I mention in this thread, you'll see the method these guys used to put panels between the posts and studs to create a barrier.
You could possibly do something similar to the gap between your AAC block and the posts, like a vertical spline. That way the post can expand and contract from dry season to wet season and not open up a gap between the AAC wall and the post.

This would mean you'd have to cut a groove down the side of each post for the spline material. And figure out some way to have a groove in the block wall for the spline as well.

Just my thoughts on the subject.

Good luck with your research.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Thehardway

Canopy,

I have built with AAC block and if you can stand the dust it is great stuff to work with.  It cuts easily with hand tools and can be sculpted and planed to very tight tolerance.  I cut most of mine with a circular saw and a thin kerf carbide blade and a stanley sharp tooth handsaw.  It will accept wood/drywall  screws when of reasonable length and driven in with an impact driver.  It is also very stable due to its inherent structure.  You will find that once you have built your AAC infill system it is advisable to protect the block from moisture intrusion.  There are coatings manufactured specifically for use on AAC block and they are elastomeric type coatings.  They seal things up quite well and will move a little where spanning a gap.  They can be had in almost any color and quite closely resemble traditional stucco.  I have several samples here on my desk made by Sider-Oxydro out of Hawkensville, GA

As Jim indicates, a spline placed in a joint would serve well both mechanically and as a means of preventing air intrusion.  I would use a spline in combination with some foam backer rod and elastomeric caulk which will move with the frame.  The AAC block can be easliy notched to accept the foam and the spline.  Make sure you use a wood specie that does not readily absorb moisture and is somewhat rot resistant.  You should find most of the exposed european frames were made of english oak which is close to our White Oak and exhibits these charachteristics.  Its tyloses give it a water resistant structure.  Although many other woods are insect and rot resistant they are not water resistant.

AAC is a underutilized material IMHO and I am glad to here someone is interested in using it.  It has some great working qualities and is very energy efficient.  The only bad thing I have to say about it is that it chips very easily at the corners. It takes a great bit of care in handling to keep your edges nice.  Of course you can patch any damaged areas but this can be a bit of a pain.

Hope this helps. Post us some pictures.
Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

Jim_Rogers

Thehardway:
Canopy will be building this house frame in Thailand out of Teak.

I drew a set of plans for him.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

canopy

Yes and teak wicks water very well due to the natural oils in it. Normally AAC blocks here are attached to the posts using brackets instead of a spline. TheHardway you are right that an expansive mortar must be used on these blocks but I have a hard time envisioning it could expand enough at the posts? See below illustration of an idea for an expansion joint. I have never done this so it is just an idea that could probably be improved of which I would welcome advice. The goal is a durable, water tight joint that is also somewhat sound proof. I might also put something like backerseal into the gap if I can find it.



Thehardway

Have you considered using something like Expand-O-Gard?  I am thinking something like this might work well.  Nail it to the inside edge of your post when your frame is built.  Then lay your AAC wall or whatever infil system you select leaving the edge outsde.  After the wall is built you screw the tab to the out side and then put your stucco coat over it all.  The rubber will move with seismic activity, temperature and moisture changes.

I am thinking something like this:


 

It lost a little when it re-formatted the graphics but I think you can get the idea.  This would seal out moisture and air as well as leave room for movement/expansion.  Of course I don't know what all is available to you locally.  You could probably use some thing as simple as a bicycle innertube  with two metal strips for attachment but dry rot and UV exposure might be an issue over time. 

The mortar we used to lay the AAC block per the Manufacturer (hebel/Xella) was a lot like thinset.  You spread it on with a grooved trowel.  The bedding layer had a bit of fine aggregate in it and was slightly thicker.   The elastomeric stucco coat you rolled on with a heavy coat masonry paint roller and apply 2 coats or more for build up.

I would love to see a teak frame.
Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

canopy

I like the spline. What is a good way to groove AAC like that? Is there any sort of angle grinder attachment that would do that? Hand tools? I'll probably also groove similarly for utility chases.

Still debating on the infill method. There are a few disadvantages. First the number of linear feet of expansion joint is daunting to go along every post, brace and plate. Second not easy to run utilities since there is wood blocking the walls in all directions.

Thehardway

Canopy,

The AAC block I worked with was very soft and very workable with hand tools.  A couple cuts with a saw to give appropriate depth/width for the groove and then remove the waste in between with a chisel of the correct width.

I'm not sure I understand what you are saying about the utility issues.   Are you speaking of your interior wall receptacles and plumbing fixtures being blocked by your posts and plates?  Does the frame have sill plates?  Are you building slab on grade? I would likely feed all wiring and plumbing up from the floor.  Once in the wall it can be grooved into the AAC or placed in pre-drilled chases.   I would have to know more about the frame design to make any better recommendations. 
Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

canopy

So AAC won't ruin good saws/chisels/drill bits? I am not yet experienced with AAC, but it makes me cringe a little bit to use wood tools on stuff that seems almost masonry.

In this case it is slab on grade, no sill. Placing fixtures and receptacles is straight forward, but the difficultly seems to be concealing pipes and wiring runs with an infill wall since each bay is enclosed by timbers. So it might involve either running conduits through the slab as you mention or if not then drilling through posts. Then it seems just a matter of notching channels through the AAC to the fixtures and receptacles. The type blocks I will use are Hebel and they allow cutting depths up to 1/3rd the block thickness.

Thehardway

Canopy,

Do not use your good chisels and saws on this stuff, they will cut it easily but it does cause a considerable amount of wear on them.  A Stanley Sharptooth works great on it or just an old handsaw.  Any sharp chisel will cut it.  I also used a standard 7" circular saw with a thin kerf carbide blade for cutting the blocks.  You can buy Hebel blocks which have a factory core for running conduit, plumbing Etc.  The bad thing is they are quite fragile when cored.  Quite a few of our pre-cored blocks were cracked during shipment.  This is the reason I chose to drill my own.  A solid block is anything but fragile and will not crack no matter how hard you hit it with a hammer.  It will just leave a little dent.  Its very strange.   A decent hammer drill with masonry bit will cut through AAC like warm butter.  Running through the block in drilled holes is easier than grooving the surface of the block.  Another option might be to treat it like a log home retrofit and use a small baseboard style box chase to feed wiring through.  This works well until you come to a doorway where you will have to bypass either above or in the slab.  Do you have any AAC samples to play with?  If not I could mail you a small piece so you can get a feel for it.  I think I still have some scraps around.  It doesn't weigh hardly anything compared to regular concrete block.  It is a lot like pumice in weight and texture and cuts similar to soapstone.

A couple of things to keep in mind with AAC.  Beacause of its porous structure it does wick and hold quite a bit of moisture.  Additionally, It is difficult to get things that vibrate to attach tightly to it as the cellular structure tends to collapse and turn to dust under it when tightened.  You must use hardware with large surface areas or something to distribute the tension force.  We did not have good luch with things like lead anchors or expanding concrete anchors although a lag screw will run into it just fine and holds well.  In many ways it acts like wood and in other ways like concrete.

Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

witterbound

It just seems nuts to me to think about all these issues with infill (wiring, sealing, etc) because you want it to look like a timber frame from the outside.  How would you infill in the brace triangles?  Same way? 

Thehardway

yes, bracing can be filled the same way if bracing is used. Typically the face of a brace is aligned flus with the exterior wall and is not the full width of the post.  The AAC block can be cut out to accept the brace.

In reality, since AAC is a structural material it can be integrated into the design and serve as the bracing, or, posts could be completely omitted and top plates mounted to the top of the wall.

This actually sounds a lot more complicated than it is.  This type of thing is done every day in commercial construction.  Just about every strip mall and big box store is built this way. The only difference here is the posts are wood instead of steel I-beam and the infill is AAC instead of CMU.  All of the slab and utility issues remain the same.

Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

canopy

Ok one last thing, any ideas how to do an expansion joint from wall to plate? Doesn't seem like a spline could be fitted there since laying the last course wouldn't have clearance.

Yes I do have access to AAC block examples. They are amazing. What I understand is they are made like bread dough; during manufacture they rise and become 80% air which gives them their light weight and insulation value.

bigshow

well, just thinking outloud: a v groove in underside of girt/beam, v-groove on top of AAC.  Put backer rod in each groove (tack in with staples, sealant, whatever).  Then, spray foam that gap something fierce.  I am thinking backer rod to decouple the spray foam from the materials, particularily the timber, to let some kind of movement happen with out the foam cracking. 

I never try anything, I just do it.

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