To build this addition,we first had to hold upthe house already there.
An Englewood addition dug to basement level against an existing foundation — underpinned in sequence, then framed, roofed and stuccoed through a Colorado winter.
The hardest additions are the ones dug next to something.
This Englewood home had a low rear elevation and a tired covered patio. The addition that replaced it goes down as well as out — excavated to basement level directly against the existing house, which meant the original foundation had to be underpinned before anything new could be poured beside it.
Underpinning is the part of this job most homeowners have never heard of and every structural engineer worries about. You cannot simply dig a deep hole next to a shallow footing; remove the soil supporting it and the house above will tell you about it. So the ground is taken out in short sections, each one filled with new concrete carried down to the depth of the new build, and only then is the next section opened.
It is slow, it is sequential, and it is entirely invisible in the finished photographs. It is also the difference between an addition that works and a crack across the back of the original house.
The finished interior · Englewood
It began as a patio, and became a hole beside the house.
The first frame is the rear of the house as we found it: a low roof, a covered patio, a garden being used for storage. Everything after it is the excavation — cut deep and cut tight, right up against a foundation that was never designed to have a basement dug next to it.
Hold up the old house, one section at a time.
Look along the wall in these frames and you can read the method: a run of pits opened underneath the existing footing, spaced so that the untouched ground between them keeps carrying the house while each one is poured. Only when a section has cured does the next one open. Then the new foundation walls go up beside it, damp-proofed before a single load of backfill goes back in.
Trusses set in snow, because the schedule said so.
Roof trusses arrived and were laid out in the garden, then set from a machine working in a yard that had been a hole a few weeks earlier. Framing through a Front Range winter is normal; framing through one with an open excavation beside the house is a planning problem, and the answer is to get sheathed and roofed before the weather has an opinion.
The last wall to come down is the one you were living behind.
The addition is built as a sealed shell first, and only then is the original exterior wall opened into it. Doing it in that order keeps the existing house weather-tight and secure for almost the whole build — the family lives behind a wall that is still a wall until the week it becomes a doorway.
The join is the part you cannot find.
Walk through it now and there is no step, no change in ceiling height and no line in the floor to tell you where the original house stopped. That is the whole test of an addition, and it is decided months earlier, at the point where a laser level sits in a muddy hole.
A freestanding tub, on ground that used to be a hole.
A marble-surround freestanding tub, a glass-enclosed tiled shower and a vanity wall with proper lighting. Worth remembering, standing in it, that the floor underneath is sitting on concrete poured section by section beneath a house that stayed exactly where it was.
Same garden, a great deal more house.
Stucco to match, a gable-end covered porch where the old flat patio cover used to be, sliding doors onto new concrete, and a re-graded garden that drains away from everything that was just built. Compare the first frame here with frame 01 of the Before section.
We’ve used AAA for multiple projects on our 2 homes. They built a new conforming basement bedroom and modernized a wood burning fireplace by building a stone facade, custom cabinets and installed a gas insert. Our sad, tired primary bedroom was updated with a new curbless walk in shower and beautiful cabinets in addition to a larger closet. We couldn’t recommend them highly enough.
Underpinning is where an addition quietly goes wrong.
Most homeowners comparing addition quotes are comparing finishes. On a job that digs to basement level against an existing house, the finishes are the cheap part and the risk is entirely in the first six weeks, underground, before anything visible exists.
Sequence is the engineering
Underpinning works because of the order it is done in, not the concrete. Open too many sections at once, or open the next before the last has cured, and you have removed the support from a house that is still standing on it. That sequence has to be designed, inspected and actually followed on site — which is a very different thing from being drawn.
One team means the engineer’s drawing and the site are the same thing
Where the designer, the engineer and the builder work for three companies, the underpinning schedule is the first thing to slip when the weather or a delivery moves. On a design-build contract there is nobody to hand it to. The people who drew the sequence are the people standing in the excavation.
Build the shell first, open the wall last
Sequencing the job so the original exterior wall stays intact until the addition is roofed and dry keeps the family in a secure, weather-tight house for almost the entire build. It costs nothing to plan and it is the single biggest difference in how an addition feels to live through.
Drainage is part of the structure, not the landscaping
Once you have dug next to a house and put new concrete in the ground, where water goes afterwards stops being a garden question. New grade, new patio falls and new steps were all set to move water away from both the new foundation and the old one.
If you are weighing a home addition in the Denver Front Range and anyone has mentioned digging near your foundation, ask how the underpinning will be sequenced and who signs it off. You can also see a ground-level addition in Denver, a second-storey pop-top in Lakewood and a two-phase remodel and addition in Littleton.
Tell us what you want to build onto.
We will look at what is standing, what your foundation and lot can carry, and what your ground will allow — then tell you honestly what it takes. It starts with a short phone consult, not a sales visit — and if it looks like a fit, we come out and look properly.
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