One of the biggest concerns that customers have is regarding the pit. Every elevator needs one, including your new modular elevator. You want to make sure you do everything right for when the elevator arrives, and this article will give you some tips to make it easy. By taking some time now, you can avoid issues and problems down the road.
On the surface, it seems easy enough. Dig and pour a concrete pit for the hoistway, with cast-in-place anchor bolts in the corners. But, when you mix in the need to engineer the pit foundation and add reinforcements based on the elevator’s pit reactions, all the while accounting for the job site’s soil conditions and your local code requirements, it can seem more daunting. Keep in mind though, we supply the necessary information, plans, and even a template (if requested) to help out.
So, to put everyone’s mind at ease, let’s cover the basics on not only the pit but also the foundation for the modular machine room, if your project is going that route. You can also find this info on our website for easier access later.
- Typical pits have 8” thick walls and 12” thick floors. However, always consult your pit layout drawings for precise measurements for your specific job.
- If you have a sump hole, cover it with a non-combustible material, typically a sheet of metal.
- Pour a concrete slab for the modular machine room, if ordered. Purchase epoxy anchors to bolt it to the foundation after it is set. If the machine room is not adjacent to the hoistway, piping and electrical must be run underground or overhead. Coordinate with PME and the installer to determine any building preparations needed to accommodate this.
- Once the pit has been poured and the anchor bolts are in place download this Pit Drawing Form. Fill out all the blanks with exact measurements and make sure to include the project name at the top. Email the form to us. With this completed form the holes on our hoistway for the anchors will be as accurate as possible.
More detail and tips include the following:
Pit Depth – You only want to pour the pit once so, pay close attention to these instructions. The pit should be exactly 4’ deep, measured from top of finished floor to pit floor. Our tower’s legs are 3’11” long, made to sit an inch off the pit floor, with grout underneath. This allows for some adjustment if the pit floor isn’t perfect. The adjustments are done by putting a ¾” thick leveling nut and washer on the anchor bolts before lowering the tower down. Adjust the nuts as needed to plumb and level the tower. Install washers and nuts on top of the tower base plates and tighten. Grout below the base plates.
What do you do if the pit is too deep? The base plates can sit more than 1” off the floor, but if the anchor bolts are too short as a result of the extra depth, extra in-field welding will be required to produce a stable connection.
Err on the long side on the anchor bolts. They should protrude a minimum of 3.5” from the pit floor, but making them a few inches longer poses no problem with installation and gives you breathing room if the pit is too deep.
(On the other end of the spectrum) Pit too shallow: If minor, this could require grinding away a bit of concrete around the anchor bolt. If major, the pit might have to be re-poured. Avoid this at all costs! Too deep is better than too shallow!
Length and Width – The pit should be the out-to-out steel dimensions plus 1” on all sides for clearance when sliding the tower into the pit. Note that the enclosure of the elevator shaft stops at the top of the pit. If needed or wanted, for above-ground pits, we can extend that enclosure down further. If the pit is too big, it’s not a big deal. However, you’ll need to make sure it’s properly flashed to keep out water and fire caulked to maintain the fire resistance of the hoistway.
Pit too small: Oops, you’re going to have to tear out some concrete. No easy fix for that.
Wall protuberances – The tower slides in right along the walls on its way to the pit floor, so it will catch on any protrusions. Once it’s set, there are openings in the structural framing that piping can be run through. Before lowering the elevator, terminate any penetrations such as PVC liner or piping at the pit wall. Run any piping/electrical after the tower is set. Note that the diagonal rods are for stabilization while uprighting the tower and may be removed after bolting the tower down, if they’re in the way.
Sump hole in corner – The base plates sit in the 4 corners and need a solid surface to rest on. If your pit has a sump hole, make sure it’s at least 12” from any corner.
Anchor Bolts – When you pour the pit, anchor bolt placement is very important for elevator installation as this directly effects where the modular elevator will be placed. Please make sure the distance of the bolts from building is right and make sure to include the building finishes when calculating where to place the “front” anchor bolts. Too far away can be bridged with flooring, drywall, and flashing. Too close means reworking of the anchorage.
Check Please – Check, check and check again! Measure three times. Check your prints twice. Cross square them. This is critical. Incorrect placement may require torching out the base plate holes, moving anchors, or other work to provide alternative anchorage. If you know in advance that the placement is slightly off, we can widen the base plate holes in the factory, which is easier than doing it in the field. We can also supply an anchor bolt template to make bolt placement a little easier and more accurate.
Other Pit Info – If the lowest stop is above grade, alternative construction can be used for the pit. The pit floor can be poured as a slab and then walled in afterwards with CMU. Also, the elevator shaft can be finished down to the pit level to provide the pit “walls.” Note that you should at least have a short stem wall to keep water out of the pit area.
Lastly, we want this to be a success for you. If you have any questions at all, contact our team. Our engineer, Tim House, is always ready and willing to help. Feel free to call or email him at firstname.lastname@example.org. Here is a video that walks you through the process of installation. You may find it helpful.