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Passive House + Zero Net Energy + Permaculture Yard

Tag Archives: Tuff II

Gravel Border Around the Foundation

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Before we purchased our empty lot we had been told that our subdivision has a fairly high water table, so managing underground moisture, especially with a full basement, was going to be a necessity.

In order to better control water below-grade we had our concrete subcontractor install drain tile on the exterior and interior sides of the foundation walls at the footings in order to maximize the amount of water that could be quickly and efficiently sent to our sump pump. Once our sump pump ejects the water outside it travels through an underground pipe to a culvert out by the street, moving with the aid of gravity, along with water collected from our neighbors’ homes, before ending up in the municipal system.

In addition to the spray-on damproofing applied to the exterior of our foundation walls, the 5″ of Rockwool on the outside of our foundation also encourages water to make its way down to the drain tile system before it has a chance to collect and sit, causing serious problems.

At grade, around the perimeter of the house, we also decided to install a gravel border, both for its decorative effect and its ability to encourage water to move away from the top of our foundation and down to the drain tile, particularly during periods of heavy rainfall.

We also considered various ways to protect and finish the top of the exposed Rockwool on the foundation. Here’s an older Green Building Advisor article discussing the issues involved along with possible solutions (as far as I can tell there’s still no single, obvious solution yet, although a parge coat or stucco finish is arguably the most attractive and durable, especially if combined with a gravel border as opposed to just top soil): GBA

After initially deciding to go with a combination of tile backerboard and Tuff II (giving the exposed insulation the look of finished stucco or exposed concrete), we ended up using metal flashing from coil stock instead (typically available in the widest number of options from a local roofing supply company).

It was only after construction began that I learned the tile backerboard manufacturers don’t honor warranties for this below-grade application (perhaps this will change in the future, or maybe they’ll develop a product for this specific application). Although I know the product is commonly used in this way (I couldn’t find an example of a bad experience, or a case of catsastrophic failure anywhere online), the lack of warranty protection doesn’t bolster confidence for its long-term durability.

In this regard, I imagine some kind of gravel border is probably essential, especially if the house would otherwise be surrounded by a lot of clay soil that likes to retain moisture. Also, just getting the backerboard attached to the foundation through the 5″ of Rockwool would have been time consuming (assuming you can find long enough flat-head concrete screws, which we unfortunately didn’t), so we opted instead for metal flashing mainly for its ease of installation and for some cost savings.

Starting on the green Zip sheathing as if it was a typical Z-flashing, we had the siding guys just continue the metal flashing down the face of the Rockwool on the foundation below where we knew the level of the gravel would end up (more on this in a future blog post regarding siding installation details). So far this has worked out well, with the metal flashing avoiding damage, and without much “oil canning”, even on the west side of the house, which has the largest amount of exposure. It probably helps that the metal flashing in this area around the house is the same color as our siding, helping it to ‘disappear’ visually to some extent.

When our excavator did backfill, knowing we were going to have to cover the Rockwool around the top of the foundation, we had him hold back on the top 16″ or so. With this ‘trench’ left exposed, we first applied landscape fabric in order to try and control weeds in the future, and to better contain the washed gravel that we would be putting down inside the trench.

gravel - west side w: just fabric

Setting up the landscape fabric.

As with many other areas of the house, we decided to opt for a more informal look, avoiding a perfectly consistent and squared-off border, preferring more of an undulating path as the outside edge of the border makes its way around the house.

gravel nw corner

Section filled with gravel.

And instead of moving around endless loads of gravel with wheelbarrows, we rented a compact front loader, in our case a Ditch Witch (sometimes referred to generically as a ‘dingo’), which made the project go much faster while also saving everyone’s back.

We had watched Felipe move gravel and other materials around during the construction of our stone window wells, so we knew just how versatile and useful these machines can be — and they just look like a lot of fun to use, which they are.

changa on ditch witch

We rented the machine from a Rental Max location near us, which wasn’t cheap, but we definitely felt like we got our money’s worth, as it saved us from having to endure many hours of hard labor. My wife loved using it, in part because the controls mimic those used in video games, so it was fairly intuitive for her as she quickly learned to precisely and accurately move the machine around exactly where it needed to go, including some fairly tight spots around the house.

We think the machine is worth every penny of rental cost if you have a significant amount of landscape material that needs to be moved, especially if a wheelbarrow is your only other option, or if tight spaces preclude the use of larger machines.

guys helping me spread gravel on west side

Luke, Jesus, and Eduardo help me shovel and rake the gravel into position as my wife drops each bucketful in place.

The boys were profoundly disappointed that they were never given a chance to operate the dingo, especially when they saw how much fun my wife was having using it.

gravel n and w views

Northwest corner of the house as the gravel border takes shape.

 

setting up gravel on west side

View of west facade as gravel is installed and we prep for boulders.

On the west side of the house we decided to add some boulders where there’s a drop-off in grade. In addition to adding some visual interest, we thought the boulders could help with surface run-off during the heaviest rainstorms.

setting up for boulders

Adding these little gravel beds helped get the boulders set securely in the hard clay soil.

We purchased the boulders locally from Lurvey. They have a nice selection of boulders and flagstones in a wide variety of styles and sizes. We would’ve chosen even larger boulders, but we were somewhat limited in this regard, having to base our selection on what we thought the dingo could safely handle.

first boulders going in on west side

First boulders going in.

In addition to the boulders, once mulch and plants are added to this area we shouldn’t see any erosion in the future.

Setting the larger boulders in place, and selecting and arranging cobblestones around the edge of the gravel border, was a lot of work, but it was also a lot of fun. I can see why someone like Lew French, or Dan Snow, gets so much enjoyment from their work:

And apart from their decorative function, and their ability to help prevent erosion, kids can’t help but try out their balancing skills on the boulders.

ninja training

Ninja in training.

 

north side w: gravel and first cobblestones

Cobblestones going in around the edge of the gravel border for added decoration and to keep the eventual mulch in the yard separated from the washed gravel border.

There will be more photos showing how the gravel border turned out in a future blog post on the installation of the siding.

nature taking back

With the clay soil left exposed around the house for many weeks, mother nature didn’t hesitate to fill the void with a wide variety of ‘weeds’, some quite beautiful in their own right.

Foundation Details (Air Sealing #1)

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Footings

For the top of the footings we used a product from Cosella Dörken called Delta Footing Barrier. Acting as a capillary break, the membrane is supposed to help prevent moisture from wicking up from below the footing, where it could then migrate into the foundation wall and into the basement, or even the wall assembly above (worst case scenario), causing mold or other moisture related damage. It should contribute to making the basement a very livable space (especially when combined with significant amounts of insulation on the exterior walls and under the slab).

Here’s a detail from the construction drawings:

footing-thermal-bridge-up-from-soil

Red arrow shows thermal bridge and gap in the vapor barrier up through the footing from surrounding soil if Delta membrane were not present.

In other words, this junction represents a weak point in our thermal envelope and vapor barrier. Passive House proponents often talk about using a red pen on a construction drawing to follow the air barrier and thermal envelope (the goal: no gaps in air sealing or the layers of insulation) . In theory, you should be able to do this all the way around the structure without once lifting your pen. If you can lift your pen (meaning there’s a gap in your air barrier or thermal envelope — which would be the case without the Delta membrane on top of our footing), then it’s a weak point that should be addressed (if at all possible).

Even with significant insulation on the exterior wall of the foundation (Roxul Comfortboard 80: 2″ + 3″), along with a sprayed-on waterproofing membrane, as well as a vapor barrier (Stego Wrap) and insulation (Roxul Comfortboard 80: 2″ + 2″) under the basement slab, this junction where the three elements meet — slab, footing, wall — is a weak point. Although it doesn’t address the weakness in R-value, at least it should keep the moisture at bay (probably the biggest complaint associated with basements).

With a 9′ basement, we’re hoping the temperatures at this depth are consistently mild enough to avoid any kind of significant energy penalty. I’m confident this will be the case because in our last home, a typical suburban tract house without much insulation, the basement always stayed cool in the summer and warm in the winter, even though the ducts to the basement had been closed off so the space never saw any direct benefit from the HVAC system.

For minimal cost in materials, the Delta membrane seems well worth it for the added peace of mind.

foundation-delta-membrane-in-box

Rolls of Delta Footing Barrier on site and ready to go.

 

Here is a video and some photos from our job site:

 

 

The guys from Tynis Concrete didn’t seem to mind trying something new, and the membrane went on without any issues.

 

foundation-delta-fabric-close-up-in-corner

A corner of the footing with the Delta membrane “keyed” into the footing.

 

I couldn’t find any local suppliers who carried the Delta membrane, so I ordered online from: spycorbuilding.com

 

foundation-mud-shot

Detail of the bottom of our hole, being prepped for the footings.

 

 

Foundation Walls with Roxul Comfortboard 80

For the walls, first we used a spray-on waterproofing membrane from Tremco:

After the waterproofing was complete, we began installing the two layers of Roxul Comfortboard 80 (a dense, rigid form of insulation that can be used below grade, to the exterior side of wall sheathing, and even under a basement slab), which will give the basement foundation walls an R-20 of insulation value.

roxul-delivered-to-the-site

Roxul delivery shows up on site (Comfortboard 80: 2″ and 3″ thick). Roxul is showing up in the Big Box stores here in the Chicago area, so it’s becoming easier to order.

When questions came up about how to install Roxul, or which product to use where, their technical help via email was great — in our case, Fiona Schofield, who gave us a lot of useful information — including the document below, a study on the long-term condition of Roxul (aka stone, rock, or mineral wool) in a below grade application (i.e. up against an exterior foundation wall):

external-thermal-and-moisture-insulation-of-outer-basement-wall (pdf)

In addition, after finding the video below online, in which what looks to be a European version of Roxul is attached to a cinder block wall with an adhesive, or a thinset mortar,

I contacted Fiona and heard back that it was ok to use an adhesive for our first layer (PL Premium, or similar polyurethane adhesive caulk), so long as we used a mechanical fastener for the second layer. In effect, the first layer just needs to stay on long enough for us to get the second layer up and attached with a mechanical fastener. This really saved us some time since the guys didn’t have to drill two full sets of holes.

sammy-butters-the-back-of-the-roxul

Sammy hitting the back of the Roxul with Liquid Nails before setting it into position. The adhesive worked really well at keeping the Roxul in place, even when the foundation was damp in certain areas.

The guys also didn’t seem to mind cutting or otherwise working with the Roxul. We used serrated knives we purchased from Home Depot, made especially for cutting rock wool…

serrated-knife-for-roxul

This knife, purchased from Home Depot, works really well cutting the Roxul.

… which worked fine, but then after some experimenting, the guys also began using a small, handheld sawzall (reciprocating saw), and even a table saw, to get the exact sized pieces we needed to ensure staggered seams. I had my doubts about the table saw, but Phil said the Roxul cut easily, and it really didn’t seem to kick up a lot of dust (although he did wear a dust mask for protection).

nils-and-bill-getting-1st-layer-of-roxul-up

Billy and Nils (in the hole in the background) gluing up the first layer of Roxul.

Once the first layer of Roxul (2″ thick) was in place, we could then install our second layer of Roxul (3″ thick) over the top of it.

After a lot of research, and even posting a question on Green Building Advisor…

Attaching Roxul Comfortboard 80 to Exterior of Foundation Walls

… we decided to go with the Rodenhouse fastener (Plasti-Grip PMF):

These really are as easy to install as depicted in the video. Using a hammer drill with a 5/16″ bit, the guys drilled a hole to the depth of the fastener, before tapping the PMF fastener home with a hammer. It’s a genuinely straightforward process. Sometimes a fastener wouldn’t sit perfectly, but as long as a majority of the fasteners on each board did, it didn’t seem to be a problem. Based on what I read online, they were much easier to work with than if we had to use Tapcon or similar concrete screws.

rodenhouse-fastener-close-up

Close up of the Rodenhouse PMF fastener.

They weren’t cheap, but they were well worth the cost in materials for the savings in labor (and frustration). And Mitch Mahler, from Rodenhouse, was easy to work with via email in terms of ordering or getting answers to technical questions.

rodenhouse-fastener-box-w-label

The box the fasteners came in.

 

in-the-trenches-w-roxul

In the trenches, as the second layer of Roxul gets attached with the Rodenhouse fasteners.

 

long-narrow-piece-of-roxul-w-3-fasteners

Long, narrow piece of Roxul with 3 Rodenhouse fasteners.

Normally, Roxul recommends 5 fasteners per piece (4 in the corners, 1 in the middle), but we found that 4 on a normal piece, and 3 for a long, narrow piece worked fine — at least for the foundation, where the backfill will help to keep the Roxul in place over the long haul.

 

 

Thermal Bridging in the Foundation

Following Passive House science principles, we tried to remove as many points of thermal bridging in the structure as we could. One area where this was addressed in the construction drawings was a 7″ thermal break between the basement foundation and the attached garage foundation. In other words, there would be no physical connection between the garage and house foundations at all. The only connection would occur above, at the level of framing, where they would be tied structurally together. The idea was that we could place our two layers of Roxul (2″ + 3″) in that gap, thus maintaining our 5″ of Roxul on the exterior of the foundation, uninterrupted (the key point here) around the perimeter of the basement foundation.

On the day the footings were installed, however, our concrete subcontractor expressed serious reservations about the long-term structural stability of the framed house and garage above this gap — in effect, he was worried that over time the two foundations might settle and move apart, wreaking havoc with the framed structures above.

So I was back to post another question on Green Building Advisor (a fantastic resource for any green build or self-build) on the topic:

How important is a thermal break between a house foundation and an attached garage foundation?

Here are some photos showing these connections:

foundation-north-corner-garagehouse-connection

Garage foundation meeting up with corner of house foundation (north side of house).

 

foundation-garage-house-connection-north-corner

Close up of this garage-house foundation connection, from inside the garage.

 

foundation-front-porch-garage-to-house-porch-to-house-connections

Front porch. Thermal bridge from garage to house is off to the far right.

 

foundation-garage-house-connection-inside-corner-of-garage-inside-corner-of-front-porch

Inside corner of garage where garage-front porch-house connect.

 

foundation-front-porch-to-house-connection-outside-corner-of-porch

Outside corner of front porch. Technically, another thermal bridge from porch to house foundation.

 

foundation-side-porch

Wing wall for side porch stoop. Yet another thermal bridge to the house foundation.

Unfortunately, there just doesn’t seem to be a lot of information available as to how to proceed. In the end, we decided to ignore these connections, hoping that the thermal bridging at these two points (garage-house, garage-front porch-house), in particular, won’t be all that significant (to our heating and AC costs, or, for example, cold getting into the foundation and then rising up and getting into the wall assembly above these two points where it could become interstitial condensation — unwanted, and potentially dangerous, moisture in the wall).

I assumed Passive House builders would incorporate rigid foam insulation into the concrete forms at these points, but I couldn’t find any pictures or descriptions showing or talking about this in books, magazines, or anywhere online. Either Passive House builders ignore these kind of connections, or I just missed the information somehow. 

*** If anyone knows of good sources on this, let me know, and I will post links here to help others in the design stage of their own build ***

Update: David Goodyear is building a Passive House in Newfoundland, and he has successfully used rigid foam between the house and garage foundations. You can read about it on his blog here:

Flat Rock Passive House: A Tale of Two Foundations
foundation-side-porch

BEFORE: Monument to Italian Brutalism.

 

side-porch-getting-wrapped-in-roxul

AFTER: Wrapped in snuggly blanket of Roxul. The wing wall was eventually entirely covered except for the tops.

Below are the other points of thermal bridging in the foundations, now covered in Roxul:

south-inside-corner-of-garage-w-roxul

Corner of garage foundation meeting up with house foundation (standing inside garage).

 

south-view-of-garage-house-foundation-connection-w-roxul

Same corner, from outside, looking at house foundation to the right.

 

inside-garage-garagehouse-connection-w-roxul

Garage-front porch-house connection (from inside garage).

 

front-porch-w-roxul

Outside corner of front porch meeting up with house foundation.

We did our best to cover these thermal bridges, but clearly it’s imperfect, so all we can do is hope there won’t be a significant energy penalty associated with these connections.

 

 

Basement Windows and Roxul

As the Roxul was going on the foundation, Phil and Nils installed window bucks for the two basement windows. The bucks were sized so they meet up flush with the two layers of Roxul. Eventually a layer of HardieBacker board and two coats of Tuff II (the product we’ll be using for the parge coat) will cover the window bucks, and also the transition between the top of the foundation walls and grade around the perimeter of the house.

nils-installing-basement-window-bucks

Nils installing the basement window bucks as the Roxul is being installed on the exterior side of the foundation.

I initially intended to use the R-Guard line of liquid membranes by Prosoco for air sealing and waterproofing all seams and window/door openings, but cold temperatures made this impossible (they require 40° F and rising, which would be the exception rather than the rule here in Chicago for December and January). Maybe because of years house painting (caulking and drywall patching) the liquid membranes seem easier to use and less fussy to get right (the big issue with the tapes is avoiding wrinkles and properly shingle flashing to get water moving in the right direction).

Our Plan B was the series of Pro Clima products sold by 475 High Performance Building Supply. Most of them, including the sealant, can be used down to 14° F without issues.

Another option would’ve been the line of Siga tapes, another popular choice used in Europe, available from Small Planet Supply.

So as the window bucks went in, I followed, applying Contega HF sealant to all the seams and gaps. The sealant is acting as our first layer of air blockage. It’s super sticky, so I don’t doubt that it’s permanently flexible. I did a mock-up of our wall assembly months ago, and the HF on the seams is still tacky to the touch. It goes on light green, then slightly darkens as it dries.

contega-hf-sealant-in-20-oz-sausage

Contega HF sealant in a 20 oz. sausage. It’s also available in the more familiar 10 oz. caulk tubes.

A few suggestions for using the HF Sealant:

  • I’ve found that completely snipping off the metal clip on the end of the sausage (as opposed to just cutting a couple of small slits around it) prevents it from getting jammed in the front end of the gun.
  • If I have a half-finished sausage of HF at the end of the day, I put it in a tightly wrapped plastic bag overnight (see photo below), which allows me to use it within a day or two without any problems.
  • Use a tiny spatula (see photo below) to tool the HF into place rather than your finger, as you normally would with a caulk — it’s just too sticky.
  • Because the HF is so sticky, I wear Nitrile gloves, so when it starts to get everywhere — and it will get everywhere if you let it — I just simply change to a new pair.
  • For clean up, the Citrus Solvent we’ve been using with the tung oil works great.
newborn-sausage-gun

The Newborn brand of sausage gun we’re using for the HF sealant. Found it on Amazon. A really well-made tool.

 

ateco-spatula

Found this on Amazon. I thought it was construction grade, but it’s made for kitchen use. It’s durable, and I like the thin blade since it offers more “feel” than a thicker blade, making it easier to tool the HF into place without displacing too much of it in the process.

It’s easy to forget the realities of a construction site when planning details, like the use of the Pro Clima tapes. I pictured it being a pretty straightforward process, not a winter day in the 20’s, fingers numb, propped up on an unbalanced ladder in the hole, while the other guys are cutting wood and Roxul around me — a case of adapt or die, I guess, and a reminder not to be too overconfident about the products you’ll be using, or the installation process that inevitably goes with them.

installing-pro-clima-tapes-on-ext-side-of-base-wdw-bucks

Applying the Pro Clima tapes to the exterior side of the window bucks.

It was important that the connection between the window bucks and the concrete of the foundation be air sealed and made water tight before it gets completely covered by the two layers of Roxul.

It’s been in the 20’s and 30’s, so the HF sealant took a couple of days to firm up before I could then apply the series of Pro Clima tapes. I’m using a combination of tapes, including the Tescon Vana (the bright blue), Profil (light blue — great for making inside and outside corners), Contega Solido Exo (black, 6″ wide), and the Extoseal Encors for our sills (475 HPBS has a great series of videos showing how to use each tape).

installing-pro-clima-tapes-on-basement-window

Finishing off the buck from inside the basement.

We knew the bucks would be sitting for some time, exposed to the elements, before the windows actually show up, so we decided to completely cover the openings just to be safe. This gave me extra practice using the tapes, which definitely helped, and it meant not stressing out every time the forecast called for rain or snow.

basement-window-buck-covered-in-tape

Basement window buck covered in Contega HF sealant and Pro Clima tapes.

The only tape that’s giving me fits is the black Contega Solido Exo. It’s thinner than the other tapes, so it has a propensity to want to stick to itself (wrinkles are more difficult to avoid), and I find it much harder to pull it away from its peel-and-stick backing than the other tapes. I worried that the Extoseal Encors might be difficult to get right, but it — along with the Tescon Vana and Profil tapes — has been surprisingly easy to work with.

This video was my Bible for installing the Extoseal Encors:

In lieu of on-site training from someone who’s used a specific product consistently, videos like this one are invaluable when using new products and you want to get the details right. Without videos like this, you’d be in for a frustrating process of trial and error.

For instance, even with this excellent video, I noticed when I did our mock wall assembly that because the Extoseal Encors can stretch around corners it’s easy to stretch it too much, thereby inadvertently thinning it out. I’ve found that when I get to a corner it’s better to just fold it around the edge rather quickly, without overthinking it too much, which helps to maintain the thickness of the material at and around the corners (arguably the product’s strongest attribute in helping to avoid water damage).

I can’t recommend enough doing a mock wall assembly, or practicing on scraps, to get a feel for using these products, before you find yourself on-site doing it for real.

basement-window-buck-before-roxul

Basement window buck sealed and taped on the exterior side before being covered in Roxul.

 

close-up-basement-wdw-buck-covered-by-roxul

Basement window buck surrounded by two layers of Roxul.

 

basement-window-buck-and-roxul-meet-up

Close up of outside edge of basement window buck and Roxul connection.

We’re almost ready to climb out of the hole. It will be exciting to watch the guys start framing so we can see the basic form of the house begin to take shape.

foundation-tools-ready-to-leave-site

Tools ready to head to the next job site. Concrete guys (they’re mostly guys) are the unsung heroes of construction (excavators should be included as well) — like offensive linemen in football, no one pays much attention to them until a mistake is made.

 

foundation-concrete-jewelry

Concrete jewelry.

 

queen-of-dirt-mountain

Queen of Dirt Mountain.