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Interior Design General

Star Decide on the look you want to achieve and develop a consistent design syntax.



It is good to try to get some consistency with the interior design.  Try to establish a limited set of ways of doing things.

You need to have somewhere to route the wiring and you need to have room to mount the power connectors and Cat-6 connectors, as well as route water pipes etc.  My solution to this is to implement a 1' 6-1/4" high (above finished floor) wainscot.  That gives a 5" wide channel for routing.

The wall above the wainscot is the 1/4" plywood of the Carnation Walling with a thin skim of interior stucco over it.

At the top of the of the wall a large cornice made from hot-wire cut polystyrene is used to provide a place for the up-lighting.  This has stucco sprayed onto it.


Master diagram

Interior master diagram 

An important thing to have is a CAD drawing that sets your dimension standards.  It sets things such as the height that your wainscoting and electrical sockets will be from the floor.  You don't want this to vary or it will look weird.



Cornices are made from Expanded Polystyrene CNC hotwire cut to a specific profile.  The size and profile is the same as used for the cupola and above the windows on the building exterior.  They can also be used above internal doorways (given the high ceiling heights).

The width is 1' 1-3/4" and the height is 10".

Internal Cornice Profile 

These are cut from an EPS ingot that is 4'x3'x8'.  It leaves some 6" thick EPS sheets as offcuts.

Internal Cornices From Ingot 

The cornice profile is also a good choice for a mantle above the fire place in the living room.  In the case of a fire you do not want it to be made of polystyrene, so you can instead use the EPS offcuts glued to the second EPS cornice piece to make a mold for concrete.



Wainscot Drawing Side View 

The wainscot provides 5" of space for routing ducting and wires.

Back corner with ledge

The wainscot 3/8" facing wood is held in place by the electrical faceplates.  This approach means that during house construction and potentially during the first year or two of house occupation it is possible to remove the wainscot plywood to run additional wires and pipes.  The downside is that it is necessary to have lots of electrical outlets (which some may consider a benefit rather than a negative).  The positioning of the electrical boxes is arranged to meet the needs of holding the 3/8' facing wood.  That typically equates to electrical boxes about every 4 feet.  Putting the facing wood joins halfway through electrical boxes results in the least number of electrical boxes (one every 4 feet), but sometimes the situation and placement of doors etc will result in more.  Using an occasional Cat6 connector mounted in the lower position is a useful substitute to help reduce the number of electrical outlets.

Double width electrical boxes are used throughout (both for power sockets and Cat6 etc), even if it means one position has a blank insert.

Wainscot height

The height of the top of the wainscot from the floor ideally should correspond to the height of the pedestal of a column that is the height of the room.  What this translates to is the following formula...
     Room height in inches / 13 * 2.67 (and then round it down slightly).

My main floor has a ceiling height 12 feet which is 144 inches, so the wainscot should be 2' 5-1/2".

My bedroom ceiling height is 10 feet which is 120 inches, so the wainscot should be 2' 0-1/2".

My basement ceiling height is 14 feet which is 168 inches, so the wainscot should be 2' 10-1/2".

(When determining electrical box heights, don't forget to allow for the raised height of the floor.)

In practice in my case the wainscot is lower because it is determined by the height of the window sills below the big windows.  For me the top of the wainscot wood shelf is 1' 10-1/2" from the concrete surface, which is 1' 6-3/4" from the finished floor.

Spacer posts

Wooden spacer posts are glued to the wall either side of where the electrical boxes are positioned.  They have three holes in strategic places to allow wires to be routed.  Typically low voltage wiring is routed through the top hole and power wiring through the lower hole.

Also marked on the spacer posts are the standardized positions for the electrical boxes.  The usual electrical box is centered 11-5/8" from the underside of the wooden shelf (ie the top of the spacer post).  There is room for eg an electrical box for a cat-6 socket above the electrical box (centered 5-5/8" below the underside of the shelf, ie 6" above the usual electrical box).

Drywall electrical support 

The spacer posts are 5" wide and are glued (using PL-Premium) to the plywood of the concrete wall. 

Drywall electrical spacers glued to wall

You can use a 4" wide spacer while the spacer posts are being glued.

Electrical boxes clamped with spacer 

The shelf is glued to the top of the spacer posts (using PL-Premium)).

Electrical boxes and sockets fitted

Once the electrical boxes have been fitted and the shelf glued on, you can measure everything to produce a hand drawing of the piece (or pieces) of wainscot facing wood needed to cover everything.  If you are uncertain of the measurements then make the electrical box holes small initially and then enlarge them later.

Drywall ready to be fitted

The holes in the wainscot plywood are cut big enough at the top and the bottom such that the wainscot facing wood just fits over the installed electrical sockets.  Don't make the hole any bigger than necessary because the hole needs to be covered by the electrical faceplate.

Drywall fits over electrical outlets

Tongue and groove facing wood

This is only 5/16" thick (call it 3/8").  This will look nicer than using MgO drywall or thin plywood.

Tongue And Groove With Dummy Joins 

5/16 in. x 3-1/8 in. x 96 in. Northern American Knotty Pine Tongue and Groove Wainscot Paneling   $6.16


The horizontal planks top and bottom can be done by rip cutting the same planks.

Each foot of wainscotting will cost about $8 (which is not too bad).

There are dummy joins between the actual joins which makes it look nicer.


Standard floor and wainscot height

The wainscot height is actually implemented all the way up from the structural concrete slab/floor.  The standard height for the finished floor above the structural concrete slab is 3-3/4".  In practice there are lots of ways that the flooring will be done in different rooms.  Sometimes it will be tiles, sometimes a self leveling concrete topping layer, sometimes 3/4" hardwood flooring, sometimes my own cut softwood.  Sticking to a standard height avoids floor level transitions (which are a tripping hazard). 

Floor leveling

It is assumed that the structural concrete slab will be level to within +/-1/2".  This variation will be taken out with 2-by planking that has an air gap underneath of between 0" and 1".  Wooden spacers are used to level the planks using a self leveling laser and a length of white PVC pipe.  When additional height is needed (as it typically is) then the air gap will be increased.  The air gap can be used to route wires, but this is not the norm because wires typically go in the wainscoting.

Spacers of length 3", width 1-1/2", and of variable heights to take out the variation and provide any additional air gap (up to about 2-1/4") are used with a spacing of about 18" to level these using a self leveling laser.  The long 2x4s and their variable height spacers are glued to the concrete using PL-Premium.

Floor gluing

The shim wood and support wood will be glued in place with PL-Premium.  Use paving slabs to weigh down the 2x4s while drying.

In the case of softwood flooring, the planks will be glued to the support lumber using PL-Premium.  Use paving slabs to weigh down the planks while the glue dries.

Water radiant heating

PEX pipe is routed in the gap between the 2x4 planking.  The 2x4s are 3/4" short near the walls to leave a gap for the PEX.  The 2-by-4 planks are 1 foot on center.  This comfortably bigger than the smallest arc diameter (10.5") that you can bend 1/2" PEX pipe.

Plastic body staples are used to attach the PEX pipe to the side of the glued 2x4s.

Wet rooms

In the case of a bathroom that is designed to be a full wet room it is best to deviate from the floor standard height and make it one inch lower.  This means the water will go down the floor drain rather than spill out of the room.  You will need a height transition of about a tile width (12") as you come through the door.


The following gives how the standard height will be achieved for the different flooring types...

Chosen cases

Softwood floor (PEX radiant heating)

Flooring Drawing Softwood 

1/2"        Air gap of between 0"-1" to take out slab height variations.
1/4"        Additional air gap.
1-1/2"     2-by-4 lumber with PEX radiant heating pipe on side.  1' on center.
1-1/2"     Softwood planks.

Tiled floor (PEX radiant heating)

1/2"        Air gap of between 0"-1" to take out slab height variations.
1"           Additional air gap (leave this out if you want the room to be a full wet room)
1.5"        Continuous surface of 2-by-4 lumber with PEX radiant heating pipe in groove.
1/8"        Thinset to hold Ditra.
1/8"        Ditra
1/8"        Thinset to hold tiles.
3/8"        Porcelain tiles.

Hardwood floor (PEX radiant heating)

Flooring Drawing Hardwood 

1/2"        Air gap of between 0"-1" to take out slab height variations.
1"           Additional air gap.
1-1/2"     2-by-4 lumber with PEX radiant heating pipe on side.  6" on center.
3/4"        Hardwood flooring.

Less common cases

Self leveling concrete floor (PEX radiant heating)

1/2"        Air gap of between 0"-1" to take out slab height variations.
1-1/4"     Additional air gap.
1-1/2"     2-by-4 lumber with PEX radiant heating pipe on side.
1/2"        Self-leveling concrete.

Softwood floor (electric radiant heating)

1/2"        Air gap of between 0"-1" to take out slab height variations.
3/8"        Additional air gap.
1-1/2"     2-by-4 lumber.
1/8"        Thinset to hold heating mat.
1/8"        Electric heating mat.
1/8"        Thinset tp protect heating mat.
1"           Softwood planks.

Tiled floor (Wooden mezzanine )

Floor is sloped towards drain, so only the edges are at 3-3/4 standard height.

At the door the floor height needs to be 3.75".  As the Ditra tiles and thinset are 0.75", that means wood threshold at door is 3".

1.5" - 3"  Concrete/mortar
1/8"        Thinset to hold Ditra.
1/8"        Ditra
1/8"        Thinset to hold tiles.
3/8"        Porcelain tiles.


Internal walling

Different types of internal walling are used depending on the need.  All walls will be constructed using 2x4 studs at 2' on center.  The outer sheeting on the wall varies according to the need and can be different on each side.  Typically the sheeting is 1.5" thick.  Sometimes EPS is used in the wall cavity to either provide sound insulation or support for the (EPS) sheeting.

Wainscoting is used for cases where assess is needed or plumbing routing or power sockets (to ensure no power socket is more than 6' away).

Wood planking

Horizontal planks of 1.5" thickness of variable width.

The planks need to be allowed time to dry and shrink before being fixed in place.

Depending on what is used on the other side of the wall, it is sometimes necessary to include a layer of eg black toughliner or geofabric to stop being able to see through.  Use 2' wide strips stapled between the studs.

Joins between planks can be avoided by using pilasters and making the planks long enough to go between them.  Pilasters have white sides and thin wainscot wood on the front.

The planks are glued on with PL-Premium.  They can be temporarily held in place while gluing using thin round headed nails and a plastic washer.  The nails go in the gap between the planks and can later be removed.  Use 2-3/8" nails.  If the wood is fresh cut from the forest, nail them temporarily in place without glue and let them do their drying and shrinking.  Even without glue it will still be a totally serviceable wall even though the somewhat ugly nails will be present.  6 months later you can pull out the nails, bunch them up to get rid of gaps, and add glue.  While gluing, you can use nails on the top edge together with props from an opposite wall.

    Nails Thin Round HeadPlastic Washers M3 



Initially just put wood on the most visible side and fit pipes etc from the other side.  In a worst case scenario it may be necessary to cut out a plank, chisel off the glue, then replace with a fresh plank.

Tiled EPS

High density (40psi) 1" thick EPS, followed by unmodified thinset, Kerdi, PL-Premium adhesive, porcelain tiles, and grout.

Between the studs to fill the cavity will be EPS, one sheet of 2" and one of 1.5".  The EPS provides support for the 1" EPS sheeting.

The Kerdi membrane stops any water from getting to the wood studs.


Use two layers of 5/8" drywall.  Use drywall that is Greenguard "children and schools" certified (even though this is still not great as it still has power station synthetic gypsum).  Stagger the joints in the drywall to ensure no path through.  Use drywall mud to make it air tight.

The other side of the 2x4 studding can have any sheeting type because the fire rating is all done on one side.

Typically, eg for the garage wall, the firewall will also have EPS insulation in the core.  Even though the garage is within the house thermal envelope you still want to limit heat loss when the big garage doors are open.

No sheeting

In some circumstances, eg inside a pantry or clothes cupboard, it is ok to have no sheeting on one side of the 2x4 framing.  You can add pieces of horizontal 2-by between the studs to make shelves.



In the area between the top of the wainscoting and the cornice, I decided to use a thin skim layer of Beadex as the wall finish.  It is necessary to fill the tie rod holes first.

I searched long and hard for the most healthy stucco to use.  Even clay earth stucco contains silica.  Some clay is just as bad as concrete from a silica % perspective.

There's a good website here .

In the end, this is what I settled on using...

For the bulk fill areas such as the 45 degree edges of windows, just use regular Sakrete concrete mix.  Like all concrete it unfortunately has lots of silica, but at $3 per bag it is a cheap fill.  For smaller fill areas use type S mortar.

For the top coat, use the lowest silica content plaster you can find.  That will be less than 5% by weight in the legal MSDS document and in the description is called "trace amounts of silica" or "percentage weight not measured".  The one I chose was Beadex Topping Pre-Mixed Joint Compound.

Topping Pre-Mixed Joint Compound   Details are here .



1)  Fill in the big voids with Sakrete concrete mix.  It is used to make the 45 degree edges on either side of the windows.   Applying it with your hands (wearing neoprene gloves) works well.  Use a cut wooden scraper jig to form the 45 degree angle.

Concrete Bagged Sakrete   Details are here .

2)  Apply the scratch coat of stucco mortar that is used for filling in smaller fill areas and getting a basically flat surface.   Applying it with your hands (wearing neoprene gloves) works well.

Mortar Stucco Sakrete 

3)  Apply the second coat (called the brown coat) to make a nice flat surface for the wall.  Typically a nice long magnesium mortar float is used to get it flat and smooth.

Stucco on ICF concrete 

Stucco scratch coat 

Stucco scratch coat 

4)  Apply Beadex Topping Pre-Mixed Joint Compound.  Use a long trowel to get it smooth.

5)  Finally the wall is painted with latex paint to seal it.


Electrical boxes

These want to all be at a standard height.  Personally I like them to be low down, just above the level of your highest floor.  The lower electrical box position (the position that is typically used) is 11-5/8" below the bottom of the wooden shelf (top of the spacer post).

It is important to mount the electrical boxes accurately, both in height and in the amount they are set forward relative to what will be the back of the drywall.  Assuming 3/8" thick wainscot facing wood then the electrical box should be 3/8" set forward.  A spacer is used to set this distance consistently while screwing on the boxes.

Electrical box protrusion spacer 

Use a clamp too get the box positioned on the height line and with the right protrusion.  Use a long extension on the screwdriver so the angle is not enough to cause the box to get pulled back by the screw tightening.  Pre-drill holes in the side of the electrical boxes.  Two screws are used on each side so the box is rigidly supported.

Screwing clamped electrical boxes

Joining wires 

Power sockets wired 

Power sockets electrical box 

The electrical sockets are wired and screwed into the boxes before the wainscot facing wood is fitted.

Electrical outlets fitted to box

Electrical wall plates

In order to hide the larger than normal holes in the drywall necessary to clear the pre-installed electrical sockets it is necessary to use the biggest height wall plates you can get.  The ones I use are from Lutron and they also look nice because they have no exposed screws.  They have a base part that screws on to the spare holes in the electrical sockets and then the top part snaps on to hide the screws.

Electrical decora plates Lutron   Purchasing details are here .

Lutron cover plate

The electrical plates are used to hold on the drywall.  Rather than using the screws that come with the Lutron wall plates, you need to use long screws, eg 1.5".

Electrical Faceplate Long Screws    Details are here .

Long screws hold on plate base 

Plate base fitted electrical

Internet Cat6

Cat-6 sockets are mounted using adapter plates that make them into Decora size inserts so that the same Lutron wall plates can be used.  They are mounted such that the tabs on the Cat-6 cables are at the bottom.

Cat6 plate and blank in box

Where necessary, put the Cat-6 in the top position, ie the secondary position.  It is also ok to put it in the lower position when power outlets are not required at that location.

(Replace the following picture with one the right way up)

Cat6 above electrical 


Flat screen wall mounting

The flat panel VESA mount can be attached directly to the concrete wall using a thin piece of wood glued to the concrete with a couple of bolts fitted.  The VESA mount plate hooks over the bolt nuts.

Mount for flat screen 

Also provided is a power outlet that will be hidden behind the drywall.

Drywall with a hole just big enough to allow room for the VESA mount is attached.


Window sills

Window sill glued on

Window sills are made from 2x12 lumber.  The width is cut such that the sills protrude 1.5" past the drywall.  The edge is rounded off using two 45 degree cuts.  The cuts are 3/8" and are done on the table saw with the blade set at 45 degrees.  Moving the table gate in by half an inch with the blade moved to 45 degrees will produce a 3/8" cut (because you lose 1/8" when the blade is moved to 45 degrees).  They are cut to size and glued on using PL-Premium adhesive.



In order to readily meet Washington State Energy code without having to have lots of discussions about the house not needing much heating given all the insulation and thermal mass etc, I decided to use a bunch of electric radiators.  To hide their ugliness, I mount them behind the drywall and provide wooden grills top and bottom.

Radiator boxed-in 

Radiator wooden grills 

Wooden grate   Purchasing details are here .


Grab Bars


Info on the type I use is here .


Extractor Fan Countdown Timer

Extractor fan countdown timer Defiant Info on the type I use is here .


Floor tiling

Tiles in wet areas need to be glued on using modified thin-set.  Modified thin-set is concrete mortar with a latex glue additive.  Because it is concrete it is not possible to buy it as a pre-mix.  Anything that is a pre-mix is a mastic rather than a proper thin-set and cannot be used in wet areas.


Window sills

Inner sills below the window

These are make from 2x12 or 2x10 lumber and are glue to the window bucking.  No screws are used because you don't want any screw heads visible.

The edges have a 3/8" 45 degree bevel on them.  This is done using a table saw with the blade set at 45 degrees and the width set to half an inch less than the wood width (you lose 1/8" when setting the blade at 45 degrees).

Once the glue has fully dried the can be sanded and blended in with the sliding bucking wood.

Window upper sills

In addition to the 2x12 lumber glued on to make the inner window sills below the window, there are also sills of the same size and bevel glued on above the window.  Temporary 2x4s cut to the appropriate length hold them in place while the glue dries.

Upper Window Sill Meets Light Screen 



It is nice to show wooden beams.  It lends detail to the overhead plane.  It does mean that you can only run ducting east west, but that is ok with the appropriate planning.

Use 1'9" pieces of 3/4" oak flooring planks over the EPS between the beams.  The planking is used to form 4' panels and then the panels are held in place using Velcro so you can get at the ducting.  A safety strap is used to hold the panel when the Velcro is detached.  Fire retardant varnish can be painted onto the wood planking.


Wood plank wall

It is nice to make one wall in a room from wood planks as it is a nice accent and makes the room feel cozier.  They can be rough cut un-sanded wood to give some texture.


Large-format porcelain tile

Large-format porcelain tiles give the look and feel of natural stone at a much lower cost.



Some people think brick is going out of fashion.  Using big timbers is potentially a better way.


TV Location

When considering living room design you want to think about the various "focus of interest".  Typically they are three "focus of interest", ie the TV, the fireplace, and the view through the window.  You want to have these separated by not more than 90 degrees (the maximum comfortable turning angle of your head).

You cannot make every seat in the living room the optimum seating position but you need to have at least two seats that are optimum.  Other people in the room will have to put up with less than ideal seating.

Ideally the center of the TV should be at eye height when seated.  That equates to 42" off the floor.

The ideal viewing distance is between 1.5 times and 2.5 times the diagonal screen width.  For a 60" TV that means 7'6" - 12'6".

There is some logic for putting a TV above a fireplace because that combines two "focus of interests" in one place, but that means that the center of the TV will be way too high for optimal viewing.

Choosing a screen

If your living room is large then you want the biggest screen you can afford.  This will allow more chairs in the room to have optimal viewing because they can be set further back so the arc distance is longer.

Personally I like a screen that has a very thin border bezel.  As well as looking stylish, this means less of the window view behind is blocked.

Secondary screen

You may decide to have a primary viewing screen and a secondary screen.  The main video entertainment will be on the main screen and the secondary screen will be used for displaying photos or news feeds or house control functions.

To allow for someone in the kitchen to not miss a vital part of the movie, it is sometimes useful to have a second screen that is also playing the main entertainment feed.


Window Blinds

Window Blinds Cherry 2in  Blinds 

When ordering blinds, specify the rough opening size, eg 36"x48".  The manufacturer will deduct half an inch from the size you specify (which makes the blinds the same size as the actual window).



In addition to the fact that heavy curtains look nice and can block out close to 100% of the light, using thermal curtains on windows is a big heat saver given that windows are a low R value compared with walls.  With my thick walls, the space between the curtains and the glass is 1' 3-3/8" in the case of a 12" concrete wall and 11-3/8" in the case of an 8" concrete wall.  Where necessary (eg to avoid the edge of the TV) the curtains can be draped into the space to reclaim some of the window sill area.

The curtains just come down to the top of the window sill (which is also the wainscot sill).  Two ties to pilasters (at seating height and head height) are provided each side of the window to constrain the curtains when open to avoid constricting the view.  Need a hook and eye on the wooden window bucking.

Curtain Ties Gold   Curtain ties

Automatic curtain opening/closing is problematical given the use of curtain ties.

A round steel pipe goes between the pilasters to form a curtain rail.  Where there is a transition from 12" to 8" concrete, a joggle is bent into the pipe.


Electrical outlets in draws

Elect Outlets In Draws 

In the kitchen and bathroom this allows appliances to be kept out of site and yet be quick to use.  Also useful for charging phones etc.