Design Below-Grade Assembly

Everything above grade gets inspected, maintained and eventually replaced. Below-grade waterproofing gets buried the week it goes in and stays buried for the life of the building. There is no drying direction, no second chance and no access, so the ordering has to be right the first time and the sequence of the trades is part of the design.

Workflow

Step 1. Take the water condition first

Ask, in one message:

Is there hydrostatic pressure: always, seasonally, or never? What is the source of that answer, and what is the seasonal range?

What does the geotechnical report say that bears on this: soil type, drainage, chemistry, gas?

What is the structure, and how is it built?

Can you get to the outside face, or is this blindside against shoring?

What is the space for, and how dry does it have to be? An archive, a parking garage and a mechanical room are three different assemblies.

Is any of it under a slab, and does the slab receive a moisture-sensitive finish?

What is already fixed: an excavation line, a property line, a shoring system already designed, a water management approach already agreed?

The tolerance for water is the design driver, not the waterproofing product. A parking garage that can drain a leak and an archive that cannot are not the same problem even with the same water table.

Step 2. Place the control layers, water first and on a named face

Present as a table, reason column in full sentences:

Control layer	Which face	Why there	Continuous at

Water, positive side or negative side. State which, and why. Positive side keeps water out of the structure and cannot be reached later. Negative side is accessible and lets the structure stay wet. This is the decision the rest follows from; do not leave it implied.
Drainage. Whether water is drained away before it ever reaches the waterproofing, or whether the waterproofing is expected to hold it. Say which, because "waterproof plus a drain" and "drain so it never gets wet" are different assemblies with different failure behaviour.
Thermal. Which side of the structure, and whether it survives being buried and wet. Note where the insulation stops relative to the frost line and relative to the floor slab, and say plainly that the joint between them is a thermal bridge nobody has quantified.
Vapor and gas. Under slabs and against walls of occupied space. If a gas condition was named in Step 1, say here that the gas barrier is a separate requirement with its own continuity, not a by-product of the waterproofing.

There is no air barrier line in the ordinary sense below grade, but the below-grade assembly still has to receive the air barrier of the wall above it. Name where that happens.

Step 3. Build the stack, soil face inward, and read the gaps between rows

#	Layer	Its job	Control layer?	Value needed from you

The last column stays as questions. A layer with no job comes out.

Then read between the rows:

Is any layer required to be installed before the structure it protects exists? That is a sequencing constraint and it belongs in the drawings.
Does anything have to survive backfill, and what protects it?
Is a drainage layer trapped where it cannot discharge?
Does a layer depend on adhesion to a surface that will be wet or dirty when the trade arrives?

Step 4. Work the joints, penetrations, and the at-grade transition

Every one of these gets named, with what the water control layer does there:

The wall-to-footing joint and the footing-to-slab joint.
Every construction joint and every cold joint in the concrete, and what waterstop is doing there.
Every penetration: services, sleeves, sumps, elevator pits.
Every tieback or shoring element left in place that passes through the plane.
The at-grade transition, where this assembly hands over to the wall above. This is the single most common failure point and it needs its own paragraph: which layer laps which, in which direction, and at what height above finished grade.
Any planter, terrace or paving that sits over occupied space.

Step 5. Name what happens when it leaks

There is no drying direction to report, so report the failure behaviour instead. For this assembly, state:

Where water would appear inside if the primary plane failed.
Whether that location is accessible, and what repair would involve.
Whether the space can tolerate it while a repair is arranged.
Whether any part of the plane can be re-injected or re-treated from inside.

An assembly with no answer to the last two is not automatically wrong. It is a risk that has to be a decision rather than an oversight.

Step 6. Report, and hand off

The control layer table, the stack table with its between-row notes, the joints and transitions, then the failure behaviour, then prose on what is unresolved. Close with the hand-offs, every time:

Drainage sizing, structural design and the geotechnical findings are open and belong elsewhere.
Where this assembly meets conditioned space, condensation-check still applies at that boundary.
The at-grade transition is a two-assembly problem and the wall above has not been designed here.

Count the open values on the face of the output. Then ask whether to write the assembly to a file and where, and write it directly, tables included.

Rules

Never supply a number. Not a thickness, not a head, not a depth, not a permeance, not as a placeholder.
Never recall a code or a geotechnical value. Both come from documents you quote.
State positive side or negative side explicitly, every run. An implied answer here is the most expensive kind.
Every layer carries a job in a sentence, or it comes out.
Name the at-grade transition in its own paragraph, every run.
Say on every run that this work is buried and unreachable, and that the sequencing constraints found in Step 3 have to reach the drawings.

Anti-patterns

Treating a damp-proofing condition and a hydrostatic condition as the same problem with a different product.
Placing the waterproofing on the negative side by default because the excavation looks tight, without stating the consequence for the structure.
Recalling a water table depth, a soil bearing value, or a "typical" membrane thickness. Those come from reports and data sheets.
Quoting a code clause found by web search.
Designing the wall and the slab as two assemblies that never meet.
Leaving the at-grade lap direction to the shop drawings.
Calling a gas barrier handled because a waterproofing membrane is present.

Resources

None. This skill is one file. Output is written directly at the path you choose.

What this does. Takes the water condition first, because it governs every other decision: whether there is hydrostatic pressure, seasonally or always, and what the drainage regime around the building is meant to be. Then places the control layers against the structure and the intended use of the space, gives every layer a job, and works the joints, penetrations and the at-grade transition. It also names, explicitly, which face of the structure the waterproofing goes on and what that does to the buildability.

What this does not do.

It supplies no numbers. No thickness, no permeance, no hydrostatic head, no drainage pipe size, no depth to water table, no code requirement.
It does not know your ground. The water table, its seasonal range, the soil, the chemistry, the presence of contamination or gas: all from the geotechnical and environmental reports, quoted by you. geotech-report-review reads that report; this assumes it has been read.
It does not size drainage. Perimeter drain, sump capacity, discharge point and what happens when the sump fails: civil and plumbing engineering.
It does no structural work. Retained height, lateral earth pressure, waterproofing that has to span a construction joint, tieback penetrations under load: engineering.
It does not check the stack. There is no meaningful drying analysis here to hand off; condensation-check still applies where the below-grade wall meets conditioned space, and the assembly says where that boundary is.
It does not resolve sequencing with the contractor. It names the sequencing decisions that are actually design decisions, which is a different thing.
It does not replace the waterproofing consultant or the Architect of Record.

What you need before starting. The groundwater condition and its source. The soil report's relevant findings. The structure: cast in place, precast, blocks, shoring left in place. Whether excavation allows access to the outside face or whether this has to go on blind. What the space below grade is for, and how dry it has to be for that use. Whether the slab and the wall are poured by the same trade in the same week.

Design Below-Grade Assembly

Workflow

Step 1. Take the water condition first

Ask, in one message:

Is there hydrostatic pressure: always, seasonally, or never? What is the source of that answer, and what is the seasonal range?

What does the geotechnical report say that bears on this: soil type, drainage, chemistry, gas?

What is the structure, and how is it built?

Can you get to the outside face, or is this blindside against shoring?

What is the space for, and how dry does it have to be? An archive, a parking garage and a mechanical room are three different assemblies.

Is any of it under a slab, and does the slab receive a moisture-sensitive finish?

What is already fixed: an excavation line, a property line, a shoring system already designed, a water management approach already agreed?

The tolerance for water is the design driver, not the waterproofing product. A parking garage that can drain a leak and an archive that cannot are not the same problem even with the same water table.

Step 2. Place the control layers, water first and on a named face

Present as a table, reason column in full sentences:

Control layer	Which face	Why there	Continuous at

Water, positive side or negative side. State which, and why. Positive side keeps water out of the structure and cannot be reached later. Negative side is accessible and lets the structure stay wet. This is the decision the rest follows from; do not leave it implied.
Drainage. Whether water is drained away before it ever reaches the waterproofing, or whether the waterproofing is expected to hold it. Say which, because "waterproof plus a drain" and "drain so it never gets wet" are different assemblies with different failure behaviour.
Thermal. Which side of the structure, and whether it survives being buried and wet. Note where the insulation stops relative to the frost line and relative to the floor slab, and say plainly that the joint between them is a thermal bridge nobody has quantified.
Vapor and gas. Under slabs and against walls of occupied space. If a gas condition was named in Step 1, say here that the gas barrier is a separate requirement with its own continuity, not a by-product of the waterproofing.

There is no air barrier line in the ordinary sense below grade, but the below-grade assembly still has to receive the air barrier of the wall above it. Name where that happens.

Step 3. Build the stack, soil face inward, and read the gaps between rows

#	Layer	Its job	Control layer?	Value needed from you

The last column stays as questions. A layer with no job comes out.

Then read between the rows:

Is any layer required to be installed before the structure it protects exists? That is a sequencing constraint and it belongs in the drawings.
Does anything have to survive backfill, and what protects it?
Is a drainage layer trapped where it cannot discharge?
Does a layer depend on adhesion to a surface that will be wet or dirty when the trade arrives?

Step 4. Work the joints, penetrations, and the at-grade transition

Every one of these gets named, with what the water control layer does there:

The wall-to-footing joint and the footing-to-slab joint.
Every construction joint and every cold joint in the concrete, and what waterstop is doing there.
Every penetration: services, sleeves, sumps, elevator pits.
Every tieback or shoring element left in place that passes through the plane.
The at-grade transition, where this assembly hands over to the wall above. This is the single most common failure point and it needs its own paragraph: which layer laps which, in which direction, and at what height above finished grade.
Any planter, terrace or paving that sits over occupied space.

Step 5. Name what happens when it leaks

There is no drying direction to report, so report the failure behaviour instead. For this assembly, state:

Where water would appear inside if the primary plane failed.
Whether that location is accessible, and what repair would involve.
Whether the space can tolerate it while a repair is arranged.
Whether any part of the plane can be re-injected or re-treated from inside.

An assembly with no answer to the last two is not automatically wrong. It is a risk that has to be a decision rather than an oversight.

Step 6. Report, and hand off

The control layer table, the stack table with its between-row notes, the joints and transitions, then the failure behaviour, then prose on what is unresolved. Close with the hand-offs, every time:

Drainage sizing, structural design and the geotechnical findings are open and belong elsewhere.
Where this assembly meets conditioned space, condensation-check still applies at that boundary.
The at-grade transition is a two-assembly problem and the wall above has not been designed here.

Count the open values on the face of the output. Then ask whether to write the assembly to a file and where, and write it directly, tables included.

Rules

Never supply a number. Not a thickness, not a head, not a depth, not a permeance, not as a placeholder.
Never recall a code or a geotechnical value. Both come from documents you quote.
State positive side or negative side explicitly, every run. An implied answer here is the most expensive kind.
Every layer carries a job in a sentence, or it comes out.
Name the at-grade transition in its own paragraph, every run.
Say on every run that this work is buried and unreachable, and that the sequencing constraints found in Step 3 have to reach the drawings.

Anti-patterns

Treating a damp-proofing condition and a hydrostatic condition as the same problem with a different product.
Placing the waterproofing on the negative side by default because the excavation looks tight, without stating the consequence for the structure.
Recalling a water table depth, a soil bearing value, or a "typical" membrane thickness. Those come from reports and data sheets.
Quoting a code clause found by web search.
Designing the wall and the slab as two assemblies that never meet.
Leaving the at-grade lap direction to the shop drawings.
Calling a gas barrier handled because a waterproofing membrane is present.

Resources

None. This skill is one file. Output is written directly at the path you choose.

What this does not do.

It supplies no numbers. No thickness, no permeance, no hydrostatic head, no drainage pipe size, no depth to water table, no code requirement.
It does not know your ground. The water table, its seasonal range, the soil, the chemistry, the presence of contamination or gas: all from the geotechnical and environmental reports, quoted by you. geotech-report-review reads that report; this assumes it has been read.
It does not size drainage. Perimeter drain, sump capacity, discharge point and what happens when the sump fails: civil and plumbing engineering.
It does no structural work. Retained height, lateral earth pressure, waterproofing that has to span a construction joint, tieback penetrations under load: engineering.
It does not check the stack. There is no meaningful drying analysis here to hand off; condensation-check still applies where the below-grade wall meets conditioned space, and the assembly says where that boundary is.
It does not resolve sequencing with the contractor. It names the sequencing decisions that are actually design decisions, which is a different thing.
It does not replace the waterproofing consultant or the Architect of Record.

Design Below-Grade Assembly

Install just this one

What this skill does

Design Below-Grade Assembly

Workflow

Step 1. Take the water condition first

Step 2. Place the control layers, water first and on a named face

Step 3. Build the stack, soil face inward, and read the gaps between rows

Step 4. Work the joints, penetrations, and the at-grade transition

Step 5. Name what happens when it leaks

Step 6. Report, and hand off

Rules

Anti-patterns

Resources

What it does not check

Files it puts on your disk

Design Below-Grade Assembly

Install just this one

What this skill does

Design Below-Grade Assembly

Workflow

Step 1. Take the water condition first

Step 2. Place the control layers, water first and on a named face

Step 3. Build the stack, soil face inward, and read the gaps between rows

Step 4. Work the joints, penetrations, and the at-grade transition

Step 5. Name what happens when it leaks

Step 6. Report, and hand off

Rules

Anti-patterns

Resources

What it does not check

Files it puts on your disk