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Home Site Map - Steps - Basement Walls and Ceiling -

Access Holes

Star It is really hard to make holes for services after the concrete has been poured and has set, so it is best to plan these holes early.


Mark main level walls

Knowing where the rooms on the floor above are helps ensure all the right holes in the basement ceiling.  Mark all the main level plumbing features (including floor drains).

You need to also 'live the basement' to make sure no holes are fogotten.

Required holes

Here are some ideas for the holes you will need through the concrete walls and the concrete ceiling/floor above.  It is very hard to make holes through concrete walls after the concrete pour, so it is important to fully plan ahead.  In addition to the holes listed below you should add lots and lots of spare holes.  If in doubt, add a hole, or preferably two.  The list below is a bit random and could do with a cleanup, but that all helps stimulate the deep thought process.

Use 4" PVC pipe collars and then the actual pipes or electricals can be fitted later.  Where there is 4" piping required then you need enough spare pipe on both sides of the concrete so a glued connection can be made.  Even when just a hole, extend 4" PVC pipe higher than concrete so a cap can be temporarily put over it to seal it from rain.

Main electric conduit from plot junction to come through back wall

The electric feed will come through the back wall of the basement.  Needs thick cable in four 2" schedule 40 conduits from the main junction panel that's to the north of the driveway.

Main water pipe from Well to come through back wall

Will come through the back wall of the basement.  The pipe must be well insulated with EPS or soil so that cold air does not freeze it.

Implement toilet and sink drain pipes for Main Level above

These drain pipes need to be in the floor above, ie in the ceiling of this level.  This is because most things are either in an island (eg kitchen second sink) or are separated from the DWV stack by a doorway.  Typically each wet area will need a toilet ring in the floor plus one for the bidet plus a bath waste pipe in the floor plus a general one for the sink and anything else.

Provide floor drain in bathroom and utility areas (Basement ceiling)

Drains in bathroom floors are a good idea and would be hard to retrofit later through the concrete.  If nothing else they guard against someone accidentally letting the bath overflow.  During house construction they may also have a role in draining water off the flat roof.
Put a drain under the Main Level bathroom and one under the utility room. Also put one under the island in the kitchen.

Plumbing and electrical holes through concrete walls and floors

Don't forget there are 2 internal concrete walls that also need holes.  Make sure you have holes for all the plumbing and electricals that are on the house blueprints.

More holes and add plenty of spare holes to be safe.

Need a few electrical sockets on the outside wall for garden power.
Need water taps for the garden on outside walls.  Need ample external garden taps.  To some extent these can be brought through the wall using the tie rod holes.

Need holes for broadband, gas, satellite coax etc.
Need ERV holes (ERV also needs to provide intake air to wood fire) (ERV ducting will be 4").  Stale and fresh air intakes are 6".
Need tumble dryer vents (unless using a condensing dryer).
Need extractor fan vents for bathrooms and kitchen.  All bathrooms need extractor fans.  Ideally even the ones that have windows (although code does not require it).

Hot (and cold) water needs to go to the garden for a garden shower and for the swimming pool.

Need a pipe to and from the rain water storage tank (which is buried outside).

Need fire sprinkler pipes.

Need trash shoots from Kitchen to basement.

Need fire ash shoot to basement from living room fire.

Need wall and floor holes as per drawings.  This includes wall alcoves eg up the stairway and for appliance garages.

Special provision is needed for the two bathrooms on the basement level (including the apartment bathroom). The toilets need to be mounted to the concrete wall using 5/8" threaded studs.  The baths are easier but even so need some planning.

Mounting brackets above baths for person lifting hoists if ever needed.

Mounting brackets for stairway inner rail.

Need a separate waste pipe to the outside under deck from the kitchen garbage disposal unit. Waste pipe from garbage disposal will be separately routed out of the house so that it can either be routed to a compositor.


Separate drain pipe for the mudroom sink (to avoid putting mud into your septic system).

Need access holes through the floors.  Lots are required.  They get services from the basement to the upper floors.  Used for lots of things such as sewer pipe, hot and cold water, radiant heating for upper floors, electricals, etc, etc.

Make sure right floor holes done to get all pipes and wires through

PEX pipes, DWV, ERV (ERV ducting will be 4"), radiant heating PEX, central vac, etc.
To do this it will be necessary to mark out where the various rooms on the Main Level will be so that holes in the floor are provided to get eg the PEX through under the fixture.
Sink drain pipes can be routed later, but if floor mounted toilets are used then their waste pipes need to come up through the concrete floor.

For central vac, need holes in the concrete floor.  The holes in the floor also serve as drainage if the fire sprinkler system goes off.

Put 4" holes under the wainscoting every 6 feet.

Floor plan drawings need to show floor holes.

Hole for a possible safe in internal concrete wall

Even if you are not thinking of having a safe (I'm not) it is still worth providing a hole for it.  Internal concrete walls are the best place.

Make sure right wall holes done to get all pipes and wires through

Outside wall lights etc.


Pipes for rain water from columns


Pipes through ceiling for central vac

The holes will come up in the wainscoting.  Use 4" holes so they can also take some wires.


Hole for mudroom fire chimney


Recirculation air for living room fire

Even though the air comes from the living room and is returning to the living room, the fan needs to be in the basement ceiling in order to avoid fan noise.


Central vac hole near living room fire for ash

Suck the ash to the mud room.  Vac is in the mud room.  Pipe needs to withstand hot ashes.  This would be a dedicated 12 gal shop vac.  The on off switch will be near the fire.


Alcoves completely through internal concrete walls

Where there is a 2-by framed hole, 1/4" plywood will be the only thing that blocks the square hole.  Make sure the holes are appropriately sized and positioned so as not to compromise the structure.  Need to fit between the vertical rebar and only cut through a max of one piece of horizontal rebar.

Need holes behind the kitchen counter to be able to install power sockets every 2 feet.  The hole in the concrete is 7" wide which makes the gap between the 2-by a width of 4" which is what's needed for a double electrical box.


Implementing the holes

The holes are implemented using 4" PVC pipe that is braced on both sides using 2-by lumber.

Hole bracing inside 


Hole bracing external 

(The pictures show bits of 2x4 to sometimes attach to the vertical bracing, but it is better to just always toenail them to the batons using 3" screws in Kreg holes.

Cut 4" holes in the 2-by lumber using a 4" joining collar as a marking template.  The hole needs to form an interference fit with 4" pipe.

Screw in place the bracing lumber on the inside of the wall.  Cut the wall polystyrene around the hole and dig out the circular piece of polystyrene.  Be careful not to let bits of polystyrene fall into the wall cavity.

Pipe bracing remove ICF EPS 

Use gentle hammering to fit the pipe after the braced holes have been made.

Utility pipe interference fit 


Utility pipe fitted through ICF 

Temporarily fill the holes with eg sponges.

Double utility hole


Inspection and utility hole


Mounting bolts for railings around ceiling openings

These are stainless steel bolts with stainless washers.


Mounting bolts for railings around porticos


Mounting bolts for stair rail


Wall hung toilet mounting studs


Wall mount toilet studs 


Inspection holes

Under all the windows and in strategic places in the walls it is good to implement inspection holes.  The functions are:

Let air out during the pour
Let you see the concrete level
Let you poke a concrete vibrator into the wet concrete to consolidate it.

A plug is fitted to the hole at the last minute as the concrete level rises.  It is held in place using wood screws.

Inspect, brace, and repair EPS (Basement walls and ceiling)

Inspect the integrity of the wall EPS in detail to find anywhere the concrete could leak out.  If necessary make and apply lumber to brace it.
Fill any holes with EPS glue or foam.


Thoroughly inspect all dimensions, window placement, etc

Inspection and double checking should have been done throughout the whole wall building process, but do a final inspection for plumb, level, true, etc as you won't be able to change things after the concrete pour.