Underpinning Stage 1
The initial procedure for underpinning is to determine the finished height that is required by the customer. We then carefully calculate the depth of the removal. Once disposal bins are on site and a soil removal system has been established, work may commence. It is sometimes necessary to remove load-bearing walls, replacing these with a new horizontal beam and steel post on a concrete footing. Temporary support for the existing house when necessary is usually vertical jack supports and horizontal beams. Disconnecting or suspending the furnace or boiler and water heater may be required at this point. The existing concrete basement floor is then removed, leaving an angle of repose around all load bearing foundation walls. Under floor plumbing can then be removed.
Underpinning Stage 2
Next we are prepared to commence underpinning pockets. Underpinning pockets are as specified in your architectural plans, typically in 3 separate phases of pockets, ranging in 3-4' lengths with varying depth of 18"-24" or more. Height of the underpinning depends on your requirements of the finished floor height. Often engineers require us to leave a 3-4" void between the new underpinning pockets and bottom of existing foundation, to pack "non-shrink" grout to compensate for any shrinkage in the concrete. Vibration of the concrete is often done to establish solidity and air removal to prevent any future shrinkage (in which case grout packing is not required). Please note, bench footings are required, instead of underpinning, generally on neighbouring walls in semi-detached homes.
Underpinning Stage 3
Now we are ready for the new plumbing stage of installation and install sump pumps, back flow valves, sewers, rough-ins for plumbing. Next, we install an internal waterproofing system, which consists of a 4" weeping tile system tied into sump pump around perimeter of foundation, to establish continuity and bleeding in foundation. A drainage mat (Delta MS membrane) is then installed around foundation walls, covering existing foundation and underpinning pockets, and draped over weeping tile and the gravel bed. A 4-6" gravel bed is spread throughout basement floor to make ready for the concrete slab. At this point in time, it is an option to install and in floor radiant heating system, connected to a hot water on demand or boiler system. A new re-enforced concrete floor (4-5" thick) is poured throughout entire basement with a smooth or rough finish as required by customer. At this point the underpinning is complete.
Underpinning Notes
All underpinning must be done with all permits in place, with stamped architectural/engineered drawings done. To get your underpinning project underway:
- Contact The CityWide Group to arrange initial consultations.
- The CityWide Group will provide you with an architect/engineer to obtain permits OR client may provide their own.
- The architect will obtain permits and have them fast tracked upon customer’s wishes.
- Date is set for work to commence.
