Tuesday, October 8, 2013

Above Floor Acoustic Assemblies, Basement Raised Floors, Porcelain Tile Exteriors

Damnation!  A power outage caused the loss of almost the entire article I was writing for this post.  Here it goes again.
Below are steel plates with screws holding the plywood floors in line with each other.  We had issues with this (plywood not flush with adjacent plywood) due to the exposed beam ceiling below - we used good-one-side fir plywood for the sub-floor, and it does not come in T&G.  With exposure to weather, the plywood warped and bowed.  The plates, with short screws, bring it back in line.  The steel was clear-coated.  Not shown are holes we drilled just after this step to accept low voltage wiring for lights.  In the background you will see the wood frame for a structural wall.  One must be careful when framing a structural wall over an exposed beam ceiling - or any ceiling.  Having the studs directly over joists is important to reduce warping of the plywood - but this is especially so in exposed beam ceilings.  We also beefed up the bottom plates of the walls to support studs which were between joists - see photo.  There is much to learn about open beam ceilings, in terms of construction finesse.  Some concepts are thus:
  1. Reduced height joists:  Joists in the exposed beam area that are not as tall as the regular joists are advantageous.  This is especially achievable if you have steel-beam joists, but heavy barn beams and other thick members would work as well.  The reduced height allows one to add some thickness of structure above the exposed beams - such as diagonal planking, acoustic floors, and sleepers and wiring chases.
  2. Use all galvanized/stainless hardware to prevent stains due to weather exposure.  Avoid making beams out of thinner, doubled members - It is difficult to double them properly due to the desire to avoid exposed fastenings.  Also, protect the assembly from wetness after the floor above is built.
  3. Beware the structural wall above:  Any wall built above exposed beams should have the studs aligned with the beams.  Point loads due to door openings are to be avoided to reduce uneven loading on the exposed beams, which would cause some beams to deflect more than others, or even twist.

On the right, we are laying in an above-floor acoustic treatment.  Above the 3/4" ply subfloor, it consists of 6mm cork, then thick foamed poly sill gaskets under 1x4 sleepers.  Sliced up roxul batts fill the spaces between sleepers.  This allowed us to run our low voltage lighting wiring above the sub-floor as well (covered by Roxul in the photo), so no wiring is visible in the exposed beam ceiling below.  Then we glued and screwed 3/4" T&G ply to the sleepers, again with short screws.  The sleepers hold the ply together, and the ply holds the sleepers in place. Much cheaper than two layers of ply.  Sound ratings unknown for this assembly, but the difference is very noticeable to our ears.  This we are doing all over the 2nd floor except in washrooms and other areas of hydronic radiant flooring.  Total thickness of this assembly not including the first sub-floor is just under 2". All the door openings were framed to accept this added height.

R-54 Insulation in the basement.  That is an R32 Batt under the 2x6 joists in the basement floor, and an R22 roxul batt will fit between joists.  Below these batts is a space made from PT lattice and landscape fabric, held up 2 to 3 inches using small PT blocks stapled to the batts.  This lattice assembly keeps the insulation off the concrete floor beneath, and provides an unimpeded 'surface' drainage path for any water in the basement to flow towards the sump system.  Any water which remains is able to dry through the insulation upwards.  Any water in the insulation can also flow downwards through the porous landscape fabric.  We were able to get the lattice material super cheap - it was culled material - an entire skidful for $50.  The landscape fabric was about $8 for 150sf.  We stapled it to the lattice.

In the next pic you see a 2x12 pine floor screwed to the joists in in the basement.  We buried the screws about 1/8" so we could later sand the floor and get a somewhat finished surface.  The boards will help to regulate moisture below the floor by passive moisture through them, but also by absorbing and releasing moisture.  The main reason for using this kind of floor - low cost (again, we were able to purchase the material for a great deal - 25% discount from regular contractor pricing) at about $1.25/SF.  This single layer of floor will become the finished floor (with sanding), so it means we can easily remove sections of flooring to inspect/service the spaces below in future.  We therefore install without overlaps and plan the layout to allow removal.  The floor feels extremely solid!  Air sealing is not required at this floor - this was determined from previous air-tightness testing on the building, so we know we are already down to Passive House levels of air-tightness.
The last photo shows large porcelain tiles we plan to use in the cladding.  These are 16x32" porcelain tiles.  The clips you see are stainless steel.  More on this later.


  1. What is shown in the last picture? Are those the exterior tiles referred to in the title of your post?

  2. Which books would you recommend describing the Passive House design strategies?

    1. This is an excellent question, and one which points to a hole in space. There is the book'Details for Passive Houses', but it is in German, and generally woefully inadequate as a cohesive arrangement of general PH concepts. Terrell Wong in Toronto is writing a book at the moment - probably due to publish within the net 3 months - but currently the answer is; I don't know of any book which actually does the job at the moment.

    2. Actually, 'Details for Passive Houses' includes significant english sections.....and yes, there is some good information in there, but the principals of Passive House Design are frequently just the principals of Building Science.

  3. Thank you for replying. Hopefully books or manuals will be made available soon. I have added your blog to my reader and will stay posted.

  4. I appreciate all of the information that you have shared. Thank you for the hard work!
    Bowed Basement Wall