September 2020

foundation – pile driving

Based on two test borings our Geotechnical Engineering Report concluded that piles, either timber or helical, were required to support the home. This seemed consistent with foundations for a few recently completed homes in the neighborhood, one was on timber piles, and a couple were on helical piles with grade beams. Our test borings reached refusal at 39 and 41.5 feet below the surface.

Our structural engineer thought that timber piles were superior from both engineering and cost points of view. The downside was concern about damage to an adjacent home from pile driving vibrations. Helicals were not a lot more expensive, but the chance of overages with them was probably greater, they would have to go down about 22′, and at that depth there would be multiple sections with joints, so if you fetched up against a rock or something before you got to depth you cut the pile off and try again in a different spot, and the different spot means you are redesigning your grade beams. So we decided to give the timber piles a go. I suppose we could have run them right up to the main deck, but our foundation design called for grade beams and concrete piers, a much cleaner looking approach, and better suited to the prefabricated construction approach as the precision of concrete piers coming off grade beams would be higher than timber piles sticking out of the ground (and probably requiring a bunch of bracing).

First step was to get the surveyor to come out and mark the pile locations. He used giant nails with pile numbers written on a piece of plastic. I was not sure whether excavation for grade beams would be before or after piles were in, answer was after, so a bit more work for the excavator to dig around the piles.

Our lot only has one home on an adjacent lot, the other side is a small park. The owner of the adjacent home was quite concerned about damage from the installation of the piles, so in addition to engaging a geotechnical engineer to monitor and log the pile driving operation we had them do a survey of the adjacent home to document the condition before the pile driving operation, and during the pile driving they monitored vibration along the lot line. A couple of piles were 15-20′ from the adjacent home. Thankfully the soil conditions contributing to the need for a deep foundation system were also conditions that were not conducive to transmission of vibrations, which remained below acceptable levels even for the piles closest to the adjacent home, and way below acceptable levels for the piles that were further away.

The timber piles were 45 foot long CCA treated Class B southern pine with 8-inch tip and 12-inch butt minimum diameters.

The piles were installed with a Vulcan #2 single-acting air impact hammer with a McDermid base. The ram was 3,000 lbs and dropped 2.4 feet. Required pile working load was 25 tons, based on that they figured out that piles needed to be driven until it took at least 8 blows per inch. As the movement of the pile slowed down they marked 1 inch intervals on it and someone stood there watching the marks and counting blows. I don’t totally follow, but they did some sort of wave equation analysis to confirm we were getting a working load capacity of at least 25 tons.

The hammer and rails for same were suspended by a crane, and the crew jockeyed the thing around to get it vertical and then started driving. I forget the size of the air compressor that they used, but it was a big one.

First pile going in!

Piles were installed to depths of 18 to 41 feet below the existing ground level. There was an intermediate layer that most of the piles pounded through (I think the crew was always hoping they would fetch up in that layer, would have been quicker that way). Occasionally they would also hit a soft spot and the pile would drop several feet with a single blow. Piles were cut off just above ground level and then we did an as-built survey, which showed that all piles were within inches of where they were supposed to be (plans indicated a tolerance of 3″, which I think we were within). We were very happy about that because it meant we did not need to make any adjustments to the plans for the foundation.

construction drawings

As we were securing our initial (Coastal Area Management, or “CAM”) approvals Turkel was preparing a purchase order that would take us through the detailed design process and the procurement and assembly of a prefabricated “package,” leaving us with a watertight shell, including windows and exterior doors, which we would then finish with a local builder (walls left open for installation of MEP systems, insulation, etc.).

The purchase order included:

Construction and permitting drawings
Permitting support
Shop drawings
Procurement and assembly of the package
- Trusses and framing, architectural glulams, etc.
- 2×6 on 16″ exterior walls
- Huber ZIP sheathing (1/2″ exterior walls, 5/8″ roofs)
- Warmboard-S subfloors
- Marvin Contemporary windows (DP50) and a Marvin Multi-Slide door (DP40)
Local builder identification/vetting/selection

The purchase order did not include:

Foundation (<=0.25″ out of square, elevations within 0.25″)
Structural engineering
MEP
Roofing, cladding, flooring, interior doors
Shear walls/moment frames (per structural engineering)

We had two main concerns with the purchase order, neither of which were show stoppers, but were still concerns:

There was no transparency into costs, for example we had no idea what the window package cost was, or what the markup on same was.
Somewhat related to that, this was a fairly large turnkey project with conveyance to us at completion, so we were being asked to assume a level of credit risk that is unusual in new home construction (where you would normally have a number of payments, with lien releases along the way, so you would never have too much exposure to your builder or a subcontractor). If we had been funding this portion of the project with any debt and the lender was paying attention this probably would have been a problem.

A prior Turkel client we spoke with had contracted directly with the window provider and also with the provider of the building components, which would have addressed both these concerns, but Turkel pushed back hard on this approach. The lack of transparency into costs was particularly frustrating as we started working through the details of the window package, more on that in a bit.

So with the CAM approval behind us the goal now was to get a building permit ASAP, and to get on with the construction. Prior to the CAM approval we had worked through some different options for structural engineering and ended up engaging The DiSalvo Engineering Company directly (rather than through Turkel, which would have added a 20% markup). The DiSalvo contract included the preparation of stamped detailed plans for the foundation and structure of the home and periodic site visits to check conformance to plans.

So on to the process of getting to building department approval of construction drawings:

5/14 – Turkel provided a DD (design development) set of plans to get the structural engineer going and to help with initial efforts to identify and select a local builder.

The DD set was provided to DeSalvo 5/19 and there was back and forth between them and Turkel. DiSalvo provided schematic framing plans to Turkel 6/9 for discussion, and we were all targeting 7/1 for a CD set we could use for the building permit submission. While this was in process we were weighing timber vs helical piles for the foundation system, discussing MEP design vs design/build, and looking more closely at the window package (SD did not give much or any consideration to air flow through the home). We were also working on a Turkel provided “builder specification” that would be used to cost out the non-package portion of the project and select a local builder.

7/1 – DiSalvo provided a foundation permitting set of drawings. At this point engaging a local builder and engaging a pile driving firm were the critical path items, so we elected to wait for a full set of plans and make a single permit submission.

8/3 – Submitted plans for permitting. Norwalk lost the plans and gave them another set a week or so later.

8/22 – Met with planning & zoning to go through their feedback, which was small inconsistencies between different drawings, need to label this and that, etc.

8/29 – Submitted updated drawings for permitting.

9/1 – Planning and zoning pointed out a few small mistakes/inconsistencies.

9/3 – Submitted updated drawings for permitting.

9/13 – Zoning permit issued.

9/15 – Building permit issued. So 13 months from signing contract with architect we had a building permit!

As we got into costing out the non-package part of the project, the main floor deck included about 355′ of steel beams (main floor deck roughly 49’x46′), about 110′ of which were under moment frames. And grade beams were mostly #6 rebar, which is unusual for residential construction. Turkel had another structural engineer that thought the home could be built without any steel, and DiSalvo said they could reduce steel a bit but the downside to that was additional concrete piers and steel to wood connections. Given where we were in the project re-doing the structural work was not an attractive option, and Turkel ended up moving the main floor deck and steel into the package, which was coming from a fabricator in Canada.

Turkel works with several different fabricators, and our purchase order indicated they would be using TekkHaus (no website any more, maybe they were acquired, or went out of business, not sure). For the steel value engineering Turkel worked with Pacific Truss Homes, so they were added to the mix with DiSalvo. The value engineering eventually went nowhere and we ended up back with TekkHaus for fabrication.

10/14 – Received final version of foundation plan with pile locations (as a result of coordination with package fabricator adjustments to the permit set were made).

2/16 – Complete construction set issued. Included additional detailing from the permit set, and incorporated a lot of work on the window package, window locations and sizes, and instead of just Marvin Contemporary went with a combination of Marvin and Integrity, more on that in a separate post.

4/20 – Final update to construction set. I think this was mainly window detailing updates.

approval process – planning & zoning and coastal (cam) site plan review/approval

Before construction could start we had to secure three main approvals:

Coastal Site Plan
Zoning
Building Department

Norwalk Planning & Zoning handled the first two of these, and we were told that the CAM approval process could take about 60 days, so we wanted to kick that off ASAP. Doing so required plans for the house, but did not require a construction set, and did not even require a final deep foundation design, it was sufficient to indicate the house would be raised and on a deep foundation system. So once the conceptual design was complete on 1/20/16 we kicked off the CAM approval process, and to avoid any potential re-work wanted to have that complete before work on construction drawings for zoning and building department approvals started.

The main takeaway on the CAM application requirements was that we needed to engage a civil engineer to prepare a site plan, and that this was likely the main critical path item. Submissions were due about 3 weeks before the plan review meeting dates, which were generally monthly. In casting around for a local civil engineer a couple of candidates would have taken us at the end of a queue of existing commitments, but Landtech was able and willing to get right into it and pursue an aggressive submission and approval timeline, so they got the gig. They started working (without an agreement in place) on Tuesday 2/16/16 and managed to submit a package on 2/18/16 for a meeting on 3/10/16.

Prior to the 3/10/16 meeting Norwalk Planning came back with some feedback on our submission. Despite our siting the home in the AE flood zone operation of the lot we were told the home had to be built to VE flood zone specifications. We tried pushing back on this, it seemed like it might be a difficult battle to win and we were happy to elevate the home and park under it. The main drawback to the VE rules is that you are not allowed to do more than minor drainage-related grading, whereas in an AE zone you can bring the lot up by 3 feet (which others in our neighborhood have done). Our slab ended up at 7.8′ (1′ above the average lot level), with AE and VE zone base flood levels at 11′ and 14′ respectively. Norwalk Planning also wanted to know more about the foundation, which at this point had not been designed (though we had started to look for a structural engineer, thinking it might be best for the same person to do the foundation and house, rather than using the geotechnical engineer for the foundation and then having him or her coordinate with the structural engineer). We got away with showing some timber piles in the drawings (which were ultimately below grade into grade beams, with concrete columns supporting the house). Finally Norwalk Planning wanted an elevation certificate, architect thought the structural engineer, who had not been engaged, would provide, surveyor wanted construction drawings to provide, and Landtech ultimately provided (with a CT Licensed Professional Engineer seal).

Landtech asked if we wanted to have a catchment area along the edge of the seawall of our lot, with grasses etc., the idea of a barrier between the rear yard and the seawall/water did not appeal to us, so we ended up with a site plan that included 90′ of buried Cultec C-100HD galleries with water shed by driveway and roof piped to same.

At the Plan Review Committee Meeting on 3/10/16 our project was discussed and there was no call for a public hearing, which is apparently something that can be required. Landtech was hoping to secure Zoning approval at the meeting the following week, but prior to that meeting our project had to be reviewed at the next Harbor Management meeting, which meeting I attended, and was unremarkable, on 3/23/16. While this was going on we worked with Turkel and Landtech on a final version of the site plan that brought the lower level slab up a foot from the average lot grade (I really had to fight for this), avoided a variance by making some adjustments to keep the mid-peak of the roof at 31′, and fiddled with siting a bit to comply with neighborhood setback requirements that were more stringent than Norwalk B Residence “height and bulk” limits.

A final submission to Norwalk Planning and Zoning was made 3/24/16. Prior to this submission I ordered a HP Designjet T120, which can print ARCH D (24×36 inch) plans. Printing multiple sets of plans out at Kinkos was costing a small fortune. The Zoning Commission approved the CAM application at its meeting on 4/20/16 with an effective date of 4/29/16. Next step was to get the construction drawings done.