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Community and Q&A

European-Style Hollow Insulating Clay Bricks

iLikeDirt | Posted in Energy Efficiency and Durability on

I just stumbled upon a type of clay brick that is apparently gaining popularity in Europe but seems totally unknown here in the USA. Example:

The bricks are hollow, full of tiny vertical cavities that trap air and, apparently in conjunction with the air-entrained brick itself, claim to render the masonry material capable of being an insulator. Some types of brick have mineral wool stuffed in the cavities. R-values appear to be roughly 1.7-2.2/inch. The exterior structural bricks are very thick; 12-18 inches. The whole-wall R-values aren’t amazing, but top out at 40 for the really thick bricks. Whole-wall R-40 certainly isn’t bad by any stretch of the imagination. And the large and interlocking characteristics of the bricks seem to lend themselves to rapid construction. They look to be fairly lightweight for their size, but have been tested to withstand small arms fire.

Does anybody stateside have any experience with these types of bricks? Any opinions? Any clue what they cost over in Europe? I haven’t been able to find any pricing online.

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  1. user-659915 | | #1

    I've seen clay bricks like this used in my part of N. Carolina in structures dating from the 1930's or 1940's. I imagine thermal bridging rather than overall R-value would be the main thermal performance concern in contemporary use.

    I've also seen them used extensively as curtain wall infill in contemporary concrete frame construction in Greece: the thermal bridging of the concrete frames alone must be horrendous but nobody seems to worry about it. Climate or culture, who knows.

  2. user-659915 | | #2

    In any case if you are interested in masonry alternatives to wood frame construction you'll probably find AAC block (Hebel etc.) a better supported and more available option, also that's somewhat more familiar to US contractors and code officials.

  3. iLikeDirt | | #3

    Yeah, AAC seems to be the local equivalent, although it seems to be popular in Europe too. The R-value per inch is much lower, though; around 1.25. You would need an almost two-foot-thick thick wall to even get a moderately reasonable whole-wall R-value of 30 (ignoring any potential climate-specific mass benefits). A wall built out of these bricks would only need to be 14 inches thick to reach that level of performance (again, ignoring potential mass benefits).

    As for the thermal bridging, to a certain extent, the entire brick looks like a big thermal bridge due to being all masonry, but there's definitely more solid brick than trapped air at the edge. There are versions that address this:

    I admit it's hard to wrap my mind around it. I understand air entrainment and trapped air in cavities, but a structural masonry unit with an R-value per inch of more than 2 seems pretty cool to me. I wonder why we don't use these things stateside.

  4. user-659915 | | #4

    If the thermal values live up to the manufacturer's claims there could be a future for this in the US market among those seeking alternatives to the standard constructional systems. Juwo would almost certainly need a manufacturing base here though to make it cost-effective as well as a trained sales/support presence.

  5. Expert Member
    Dana Dorsett | | #5

    There can be surface spalling /flaking issues with some of these blocks in cold/very cold climate (colder winters than central Europe), but different firing temps & glazes can probably adapt them for use in colder climates too.

    Making them truly air-tight over the long term is still an issue, as it is with CMU or other masonry builds, but more important here.

    Insulating terra-cotta blocks were in fairly common use in the southwestern US prior to about 1925 or so, and terra-cotta decorative siding was in use in many parts of the US in the late 1800s. The higher structural strength and low cost of site-made cinder block (and later factory manufactured CMU) is what probably what ended the clay-block biz in the US. Similar products have been in use in Latin America forever. Terra-cotta roofing tiles seem to have hung on in the southwestern US, even as the structural terra cotta market faded.

  6. AdamM | | #6

    Hi, it has been a long time ago when you posted, are you still intereted to know about porous ceramic bricks? I am an engineer from Poland/EU and I know this technology a little.
    These bricks are used to build complete house structure. Externall walls, internall construction walls, if needed and also partition walls.
    These bricks are made of clay mixed with carpenter's sawdust. During baking, these sawdust burns inside the clay causing gas and making little holes (smaller then in AAC, it is called porous ceramic). These holes improve the thermal resistence which is achieved by air spaces inside the clay. The clay may bee empty inside or with mineral wool inserts as you mentioned.
    These clay brick to meet EU insulation standards need to be extremely thick - the optimum R value according to EU norms, need to make a wall of over 1 Foot thick (38cm). Difficult to manage such a thick walls in family house, therefore usually are used thinner bricks plus light insulation from outside (EPS or Hard Min Wool) e.g. 20-25cm clay + 15cm thermal. This is still a lot, however this is the way, most european homes are build. This is because of tradition and the fact that forced air heating/cooling is not so popular in Europe. Usually the heating is gas operated water based system with radiants hanging at walls and pipes going arount the house connecting the radiants. Also in-floor radiants are used or heated floor. Thick walls are working as a heat condenser. Consider that natural gas in Europe is ca 3x more expensive than in the US - so the thermal efficacy is a key in EU houses.

    Such a clay brick need to be covered from outside because it is porous and attracts water. This is mandatory to use parget to cover and protects the outside walls. From inside - drywall or gypseous parget. Vinyl siding or similar covers are rarely used in EU.

    ther is a nice movie here: about the latest Wienerberger Porotherm innovation - build with bricks without a mortar (spray foam instead). it explains 90% of building process by use of clay bricks.

  7. GBA Editor
    Martin Holladay | | #7

    This is an old thread, but here's my comment: In some countries, residential builders are familiar with masonry construction, but (due to the lack of nearby forests) totally unfamiliar with wood framing techniques. In these countries, various types of masonry blocks are commonly used. In most cases, the resulting walls aren't as well insulated as the walls we promote on GBA.

    Local traditions dictate different construction methods. In general, it wouldn't make much sense for a builder in North America to fall in love with a construction method developed in Europe for European conditions -- especially if the materials have to be imported from Europe.

  8. gary_handel | | #8

    Martin, Any reasons besides difficulty of importing materials that would make you hesitate to use Porotherm? I live about 90 miles NW of NYC in the Catskills where practically all construction is stick. Watching buildings go up here is almost painful. The length of time it takes to frame a house from 2x4's and how shabby it looks has convinced me that it will be worth the trouble to import clay blocks. The result will be a much stronger, quieter, more comfortable and longer lasting home. The fact that wood is available, cheap, and suits the knowledge and economies of local builders is hardly reason enough to use it.
    I'm about to build a home for my family and intend on using clay block. If you know any reason why it would be a poor choice of material in New York I'd love to hear it.
    Thanks, Gary

    1. Expert Member
      MALCOLM TAYLOR | | #9

      User ...209,

      Can you expand on how you are considering using them? What is the wall from outside to in? Why is the floor and roof construction?

  9. gary_handel | | #10

    We have just finalized the plans and my architect/engineer is only now beginning the engineering, deciding what size of block to use and if additional insulation or a cavity will be required. I spoke earlier today with an architect in New Zealand, and his comments convinced me they will perform very well in the summer, especially with the increased rain we've been getting
    ( ). My arch. intended to include mechanical ac- the Daiken mini split units, to control humidity, but I doubt it will be needed with the clay blocks. My wife has relatives in Germany that built with Porotherm using no added insulation besides 3 layers of lime stucco and have been happy, though I think it's a little warmer where they are.

    1. GBA Editor
      Martin Holladay | | #11

      The main question I would ask the architect or material supplier is: "Can you tell me the R-value of this wall system?" Ideally this R-value would be verified by a third-party laboratory.

      In the U.S., homeowners who think that wood-framed walls are insubstantial -- a fairly common opinion shared by immigrants from Europe or the Middle East -- often choose to build with insulated concrete forms (ICFs).

    2. Expert Member
      Dana Dorsett | | #12

      >"My arch. intended to include mechanical ac- the Daiken mini split units, to control humidity, but I doubt it will be needed with the clay blocks. "

      Clay blocks are not some sort of magical humidity control material. If you live in a humid climate the will still need mechanical dehumidification/latent-cooling to stay in the human-healthy range.

    3. natesc | | #13

      A little warmer is an understatement. Western Europe gets nowhere near as cold as the Catskills.

      You will have average lows around 10-15F in the winter, where Germany will have average lows around 30F. When we spend extended periods below 0F (which the vast majority of western Europe, even Scandanavians, have never experienced) every winter, you will not be able to keep your house up to temp without a very large heating system.

      You could stick frame a house with lots of insulation that will be more comfortable for less money.

  10. rwaldron | | #14

    I have a detached garage that has been decimated by termites, and I thought this might be a good material to replace the walls with. I just can't seem to find a single place in the U.S. where I could get the block. I might not mind paying a bit of a premium, but I'd like to figure out roughly what that premium would be (i.e. would using clay blocks make the project completely cost ineffective?). Does anyone have any advice as to procuring these in the U.S., or cost info?

    1. GBA Editor
      Martin Holladay | | #15

      R. Waldron,
      Q. "I just can't seem to find a single place in the U.S. where I could get the block."

      A. I have no idea why you would want to use a hard-to-get European clay building block to build a garage in the U.S.

      If you are worried about termites, use ordinary (cheap) concrete blocks, also known as concrete masonry units (CMUs). There are available anywhere in the U.S., affordable, and of no interest to termites.

      1. rwaldron | | #16


        Maybe I have an adventuresome attitude.
        Maybe it's that an 8'-tall x 20'-long wall would be a good test subject (I plan to replace the other wall with some columns to make it open up to the back yard).
        Maybe I am afraid to present a CMU wall just inches from the property line to the city for permitting (Heck I've heard rumors that the city has been hard on any concrete structure recently due to green house gas emission concerns).

        1. Expert Member
          MALCOLM TAYLOR | | #20

          Isn't one of the main advantages of the clay blocks their insulation value - which wouldn't be useful in an open structure?

          I'm just speculating, because I don't know where you are building, or under what code, but I'd imagine the hoops you have to go through to get a European masonry unit approved might dwarf any potential problems with CMUs.

  11. GBA Editor
    Martin Holladay | | #17

    Q. "Maybe I am afraid to present a CMU wall just inches from the property line to the city for permitting."

    A. Whether you build the wall with terra-cotta blocks or CMUs, you'll still need stucco on the exterior. When completed, the two walls will look exactly the same.

    1. rwaldron | | #18

      Stucco is probably going to be my saving grace in all of this. The existing 2x4 framed wall is stuccoed, and since it is so close to the property line I'll need to sell this as a repair, not a new wall. If I didn't already have stucco, call it a repair would be a harder sell. Whether I do crazy European clay block or traditional CMU, I want to avoid a timber frame in a structure that is practically open to the outside. Also, I think the stucco might be the only thing holding the roof up at this point.

  12. gary_handel | | #19

    I will be placing an order next month for some Porotherm- being delivered to Roscoe, NY. For more information:
    Probably I could get some for you. It would likely be arriving in August.

    1. rwaldron | | #21

      Do you mind if I ask what you're paying?

    2. greenjoe | | #27

      I as well am interested in how you ordered the Porotherm blocks. I watched numerous videos by Wienerberger on the merits and installation of this product. I hope that they are represented at the 2020 Clemson Brick Forum, October 5-7, 2020.

  13. gary_handel | | #22

    I don't know yet, probably not for two more weeks.

  14. ethan_TFGStudio | | #23

    "Asking for a client..." How was the experience importing Poratherm? Have you started building with them yet?

  15. gary_handel | | #24

    Man plans, and God laughs. Arch plans are stamped and approved, permits issued, perc test complete... but a project I need to finish first has dragged on, AND, my wife and I had a great trip to Maine. We're now considering building our house there, where waterfront property would be affordable for us. So I can't tell you how it worked out importing the Porotherm clay blocks and building with them. Sorry. Stay tuned...

  16. Expert Member
    Dana Dorsett | | #25

    >"We're now considering building our house there, where waterfront property would be affordable for us.

    Be sure to plan accordingly for sea level rise if you hope to hand it off to your grand kids some day. The hurricane storm surges can be pretty serious enough on their own (speaking as someone with a relative in Maine whose waterfront property has been flooded 3x in the past 40 years by storm surges.) But if the western Antarctic ice shelf keeps going the way it seems to be going, most of the existing waterfront property in Maine would only be accessible with diving equipment or submarines in 100 years.

    For building new, a hill with an ocean view that's a reasonable walk to the water is probably a better long term bet than building 25-50' above the mean high tide, where even now in a worst case scenario it can get tagged. (My friends in Nova Scotia who toughed it out through Hurricane Juan a few decades back are taking the projected track for Dorian pretty seriously for next weekend, moving stuff to higher ground.) Depending on how far offshore Dorian actually tracks it could end up being flood #4 for that beachfront place in Maine too. :-(

    Don't mean to be harshin' on yer mellow, but keep track of the storm surge levels in Maine and the Canadian Maritimes this week if and where Dorian actually makes landfall. No matter how bad it is, it'll be a lot worse in 50 years, worse still in 100 years.

  17. tenember | | #26

    Loving this debate. On a trip to Bavaria I saw homes being constructed with Wienerberger blocks and I would like to build the same style (white stucco exterior, thick walls with deep window sills) in Maine some day.

    That said, I know nothing about building, so I'm really interested in the pros and cons of these blocks, and whether there are other construction methods that can achieve the same look but are better suited to our climate or available materials.

  18. Lars_of_NM | | #28

    These are not your grandmothers blocks....They are nothing like the terracotta blocks common in the US in the 20's.
    I was in Transylvania and Budapest in ~2014 and visited two friends that were building homes using this method. These blocks are about R-40 and do not contain any filler in the cavities. They are very common, and everybody uses them both in the city and in rural areas so they must be one of the cheaper ways to build. They are probably equivalent in cost to CMU's here in the US. In construction that is several stories, which is pretty common, a concrete structure was poured, and then the walls were filled in afterword. The stairs would also usually be poured as part of the concrete super structure. Heating is almost always hydronic. The houses I visited, had radiant heating in the floor and walls. They can do cooling using the same system and circulate chilled water. Interiors are usually plastered or tiled, exteriors are stucco. The blocks interlock and no mortar is used on the sides, just a layer of mortar between courses. The blocks are around R-40, sometimes rigid foam insulation is used on the outside of the building to increase the R value even more. Wiring is glued to the interior walls and plastered over. All windows are like submarine hatches with triple silicone gaskets. All windows are casement, no one uses side sliders because they leak. Bathrooms are usually all tiled with a floor drain and very large. The washer is usually in the bathroom since this is the wet room, dryers are not common and people line dry their clothes. Overall I was very impressed with the building envelope design. Less so with the plumbing which many times uses smaller drain tubes.

    There was a comment about it getting colder in US than in Europe and these wouldn't be good in cold climates. It gets pretty cold in the Transylvanian alps and this technology is used allot there. As far as importing these bricks, they are not that heavy but I can't imagine that would be cost effective. The technology is pretty simple, it is just an extruded brick with some sawdust in it, there is no reason these can't be made in the US.

  19. Goodmanheat | | #29

    Wienerberger, Hebel AAC or Ytong AAC would all work in the US. It's called quality construction over quantity. Air tightness, disaster resistance, longevity. Could you imagine if the houses in New Orleans or hurricane prone coastal areas were made from those product. Insurance rates would be a little lower.

  20. Dadams | | #30

    Having walked several projects in Germany out of intense interest in comparative methods and materials, a couple comments: Blocks come in many sizes; older homes seemed to have thicker walls made of bigger blocks, I saw a remodel which seemed to have the long dimension of the block being in/out increasing the thickness of the wall! New-built houses had thinner block laid long axis left/right along the wall, with external insulation as required to meet R-goal. As to wiring, I've seen them plough free-form trenches through this stuff directly from box to box with a mini-jack-hammer, embedding electrical wire a few cells deep in the block and then mortaring over the wire slot. Very fast, but would be a bitch to re-wire. But second the old comment that houses built this way are pretty permanent and usually retained in the family. I too am interested in using these for structure with a similar "permanent" goal, with eg 4" external Roxul Comfortboard 110 and a rain screen. Would be a cakewalk for our masons. But, am also still looking for pricing toward economic viability test. A 40' container can transport over 20 tons for about $3-4k transport cost.

  21. gary_handel | | #31

    I've confirmed an order with Porotherm for the materials to build a house this spring in New York. I don't have a GC (none interested & available where I live) but am looking for a construction manager to assist with at least the initial build, through to having a sealed house (roof, windows & doors). If I found someone qualified who was interested in the clay block construction I would provide them with housing and a per diem.
    Even with the now greater shipping costs I think we'll end up with an excellent and still reasonably priced home by using the Porotherm blocks, certainly one much better than the typical stick construction used in this area. If anyone has recommendations I'd be happy to know them. Thanks!

    1. AJSA | | #32

      Hi Gary,

      How was your experience working through the order process with Porotherm? Can you tell me what the cost is going to be? How much are the Porotherm bricks, how much is the shipping/import cost going to be? Have you been able to calculate a $/square foot estimate?
      I am married to a European and we are planning to build a house within a year, and we really want to use the type of materials that are commonly used in Europe, both for sustainability and longevity, as well as heating/cooling efficiency. Based on the widely varying climates in which Porotherm is used around the world, there’s no obvious reason it can’t work beautifully here in the US, too. We are just in the beginning phases of working out where to source the materials, so any information you are able to pass on would be greatly appreciated!

      1. gary_handel | | #34

        Hi AJSA
        Porotherm experience: Early on we connected with a French Porotherm rep working in Central America who is anxious to see some homes built in the US, so he has gone far out of his way to help us. We committed to an initial purchase order last month to lock in 2021 prices (that were going up 8% for 2022). The total order for the house came to 75,000 Euro's. This includes interior walls. I don't know how much we are benefitting from our relationship with this person, so I'd rather not quote the prices we're getting for the individual blocks. We'll primarily have CLIMAmur 36. What climate are you in? It's too early for me to encourage you or not based on our experience, but we're very excited and moving forward.
        Best wishes,

    2. Expert Member
      MALCOLM TAYLOR | | #33


      Have you run this by your municipality yet? I'm curious as to how they are viewing this type of construction from a building code perspective.

      1. gary_handel | | #35

        Hi Malcolm,
        Yes, and all good. We live in a fairly rural area, the house will be far from any property lines and not even in view most of the year, so safety and meeting code requirements are the only concerns. European/International standards I believe are typically as high or higher than what is required in most of the US. This product is approved and used all over Europe and has been for decades. Was there any specific issue you were concerned about?

        1. Expert Member
          MALCOLM TAYLOR | | #36


          Things may be different where you are. Our code has specific approved materials and methods. If you build outside them you need an engineer to stamp the deviations. It's not usually insurmountable, but something to be prepared for.

  22. gary_handel | | #37

    Hello everyone...(this is a cry for help), After years of planning and not planning during Covid delays, our Porotherm blocks will soon be sailing across the Atlantic. Never mind that shipping costs have never been higher. Unfortunately I do not have a local builder and by default am self building, a process contributors to this site suggest is possible. Until now I’ve had conversations with local masons, plumbers, roofers, etc., but not having had even vague dates, couldn’t schedule anything. We’re in a somewhat rural area that was already short of qualified tradesman. It’s proving very difficult for me to put this build together. If anyone could suggest where I might look for a construction manager, preferably, but not necessarily someone familiar with block construction, I’d be very appreciative. A fellow who has worked with Weinerberger building Porotherm houses is willing to come to the US to supervise that end of it, and I have masonry workers to assist with that part of the build. But there’s a lot more to coordinate and I’m not sure if I want to learn while doing, or if that’s even possible for me. Maybe there’s someone interested in seeing a Porotherm house get built in the US I could hire? Thanks for any suggestions.

    1. Expert Member
      Deleted | | #38


  23. charlie_sullivan | | #39

    I gather this is "90 miles NW of NYC in the Catskills", in Roscoe NY? That might help people figure out whether they could help or have a recommendation.

  24. gary_handel | | #40

    Thanks Charlie. I didn't want to go on too long with all the details, but I recognize at this point we may need to 'import' talent, and possibly figure out housing and a per diem. So far as geography, it would be good to have experience building in similar climates and dealing with freeze issues.

    1. WillieMartian | | #41


      I just created this account to ask for an update from you. How is your project going? When I finally end up getting laid off from the oilfield, I'll go learn to be a damn red brick wall installer for the whole US.

      I used to date a girl in Austria and I was so impressed with the quality of the buildings there that I wanted to replicate the same style in the US (I'm from Texas). I am in the process of closing on some land and day dreaming about the house prospects.

      1. gary_handel | | #42

        Hi Willie, Glad to hear there is someone else interested in my wife's 'discovery'. I need to run out now, but attached is the garage we built this fall, still waiting for a little warmer weather to finish the roof and the exterior render. Later today I'll send more details.

        1. WillieMartian | | #43

          Yeah, I'm very interested to hear how everything comes together. Did you end up building it yourself or are you hiring someone? Is that the 75,000 euro worth of the brick?

  25. gary_handel | | #44

    Hi Willie, Sorry for the delayed reply. I'm now in Greece, and going next week to Germany to see the houses my wife's family has built from Porotherm. The garage I sort of built myself, with the help of various subs, day laborers, and friends. In my dreams I find a qualified builder interested in learning about clay blocks who I could hire to supervise everything, but this magical person hasn't appeared yet. I ended up paying for (12) 40' and (1) 20' shipping container from Germany and France to get all of the blocks and dryfix to build the garage pictured and a 4,000 sq ft house. The cost of the shipping makes it completely impractical. The cost of the block by itself might be close enough to other materials and prices currently in the US that it almost makes sense.

    1. Simon_S | | #45

      Gary, Interesting project. If I had the time, I would jump on this opportunity if only to learn how to use these blocks. I was one of the first people in the US to use ICF to build a motel in Niagara Falls NY in 1992 which is a building that will be there for centuries and looks like it was built yesterday. I am still baffled why ICF is not accounting for 50%+ of the new homes in America. As the cliche goes "hard to teach an old dog a new trick". You are right that the shipping costs make this an impractical solution. 12-½ containers even with the back to earth shipping prices was still not less than $4.5K each, I think one of the European manufacturers should realize the opportunity and establish a manufacturing facility in the US. I remember back in 1992 there was only one supplier of ICF and today there are a couple of dozen so the same will happen as soon as people start experimenting with these unique blocks. I am now in California since 1996. I am still not sure these will pass code in California where you need to secure the blocks to the foundations (earthquake related) at least every foot along the perimeter. Keep us posted on your experience with Porotherm on the actual house build.

  26. canada_deck | | #46

    For an entertaining video of a very interesting build with these bricks, check out this video. If you turn on CC, he has provided a text description of what is going on. Note that he does use exterior insulation.

    My guess is I will never see this on the west coast due to earthquake concerns.

  27. gary_handel | | #48

    I'm meeting next week with a cement contractor I want to hire. My plans specify 10" of XPS under the basement floor. The cement guy says code is 3" under the basement and the ground is already over 50 degrees. He thinks 10" is extreme and serves little to no purpose. The plans also specify 10" of XPS under the footings of the house. The cement guy says he won't take the job if that is required- he has never put insulation under footings and he thinks it will compress. Should I hire another architect or engineer to consult and give me a 2nd opinion?

    1. Expert Member
      MALCOLM TAYLOR | | #49


      I should say again, I know next to nothing about this method of construction, and maybe there is some logic I'm just not getting, but the insulation in the section seems odd.

      - What is the advantage of having a thick layer of exterior insulation below grade, if it doesn't continue above where the DeltaT will be higher? I have the same question about why there is rigid foam under the footings? If the wall needs more insulation than it has, it needs it above grade too - or it doesn't need it below.

      - I agree with your concrete sub. 10" of sub- slab XPS make no sense anywhere.

    2. Simon_S | | #50

      Gary, I would definitely get a second opinion from a concrete structural engineer about the 10" XPS under the footing. For simplicity's sake let's assume you have 20 feet between the opposite footings, and let's consider a 1 foot cross section in the direction of the footing. So each footing is now carrying the load / weight of 10 feet of "building" over 2 sq. foot area or 500% more load per square ft than if you had constructed the building on a huge deep concrete slab. Furthermore, XPS has some compression and the compression is linear so the higher the thickness the more it will move. Compression in and off itself is not bad but uneven compression can spell disaster and I believe that is what this contractor is concerned about. If the soil under the building perimeter (hence the footer) was equally "stiff" everywhere and you are sure the footer will never ever crack, then by all means the entire building will settle uniformly as the XPS compresses. However, in real life, you have areas that have more ground water flow than other areas hence you get variability in the soil stiffness and you are then asking for trouble. Also, it is a safe assumption that the footer will develop cracks. Of course I am offering an opinion without knowing anything about the specific soil conditions in your area. However, I did live in NYS for many years and I know some areas have tremendous ground water, and of course the heavy rains and snow melt etc mean soil variability. Suggestion: I would consider replacing the formed 12x24" footer with an "as excavated" minimum 24" x minimum 12" trench footing that is 1 foot deeper. This should be a little cheaper than a formed footing (lot less labor) but the savings are offset by having to pour 1 additional foot of concrete so it should cost about the same. This suggestion will result in using less "aggravated/disturbed " soil which will have better structural integrity. Then put in a thicker layer of XPS along the external side of the footing instead of under the footing. I realize there will be some "thermal leakage" getting around and under the footing but it will be minimal and a much better problem to have than your footer moving / cracking and all the issues that this will cause above.

      1. Expert Member
        MALCOLM TAYLOR | | #51


        Whether you excavate a trench to pour the footings in, or excavate the whole footprint of the building, you are still building on undisturbed soils of the same bearing capacity. People use trench footing to save money, not to increase the footing's strength.

        1. Simon_S | | #52

          Malcolm, I disagree with you on this. When you trench pour you are leaving the sides also undisturbed which is not the case in a formed footing. You end up with not only additional lateral support but additional vertical support. In the formed footing, you excavate on both sides of the footing that is later refilled with much less compacted soil than the original soil and a nice path for water to flow into. If you read my comment carefully, I suggested to use the savings from the trench pour to go a foot deeper than Gary was planning (ie build beyond code requirements) to achieve additional strength, support and insulation

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