37 Long Island Circuit Craigieburn VIC 3064
House Restumping Melbourne
It is defined as replacing the old stumps or blocks with new stumps or block under the house foundation or structure.
Restumping is also called as Re blocking or re-blocking or re blocking.
Reasons why sumps need replacement or why I need Restumping/re-blocking for my house?
If there is a soil movement, the house stumps start to sink in the soil.
If the existing stumps have been exposed to lot of moisture from very long time, the stumps start to get decay or rotted out.
Does my house need Restumping and different signs to look out for?
Cracking of the interior brick walls of the house
If the floor of the house is uneven or soft or even bent
Cracks on the exterior of the brick walls especially diagonal.
Doors and Windows of the house looks apart from the surrounding walls or they are tight to open and close.
When the doors and windows are jamming.
Why stumps sink?
Stumps sink due to change in moisture content of the soil. When reactive soil (like clay) is used instead of normal soil the stumps sink. If the construction of the house or building is done on clay the soil will be unstable and will lead to sinking of the soil, which can damage the complete foundation of the house or building. If the stumps are installed on loose soil then eventually the stumps will start to sink. It normally occurs near the beach side houses.If the stumps were undermined or neglected where there was digging close to the stumps or blocks. This normally occurs while digging trenches or pipelines or even while digging for the purpose to build swimming pool.
Usual causes that needs restumping
Effect of trees: Sometimes the tree roots absorb the moisture of the soil in the surrounding areas.
Effect of site or house or building drainage pipes and leaking pipes:
Due to constant leakage from the pipes, the soil becomes too moist and tends to become loose and this causes the soil to sink.
What is Bracing?
It means providing support to structure or foundation. Bracing is attached to studs to provide lateral support to wall framing.
Materials used for Bracing
Metal straps, timber or sheet bracing.
What is lateral bracing?
Lateral bracing is the term we use to refer to any pieces on a bridge that help keep the sides (trusses) from twisting. It also helps keep the top chords of the bridge from bending or deforming in or out. In the figure above, the lateral bracing is marked red.
When do we need bracing or Lateral bracing?
Lateral bracing is required when stumps are higher than 1.2 mm
What does Restumping or re blocking include?
Changing the old stumps to new stumps
Levelling the floor
Changing the rotten sub-floor timber (this includes bearings and floor joints).
Depending on the condition of the floor changing the base boards if needed.
What is a subfloor?
Subfloor is a system of bearers and floor joists. It is used a foundation for a floor in a building. It is the bottom most layer and it rests on joists; on this layer all the other layers rest and take support.
The span of the bearers and joists depends on the load they carry and the cross section of the bearers and joists.
It is important to choose the right type of subfloors.
Sub-floors in Melbourne, Victoria
Most of the existing houses in Melbourne, Victoria, Australia; their sub floors are F8 hardwood.
From past few years F17 hardwood sub floors are being used.
Difference between F8 handwood timber and F17 hardwood timber
|F8 hardwood timber sub floors||F17 hardwood timber sub floors|
|F8 is not dry timber||F17 is dry timber|
|F8 timber shrinks during a period of time||F17 does not shrink, since it is dry timber.|
|Bearers: 100x75mm for F8 hardwood||Joists: 100x50mm for F8 hardwood.|
Pier and Beam Underpinning Method
It is also termed as base and beam method which was implemented after the second world war. This method progressed because the mass concrete method couldn’t work well for a huge depth of foundation.
It is found feasible for most of the ground conditions. Here reinforced concrete beams are placed to transfer the load to mass concrete bases or piers as shown in figure 2.
The size and depth of the beams are based on the ground conditions and applied loads. It is found economical for depth shallower than 6m.
Once the curing is done, the next excavation is started.
In this process of underpinning technique, the load is transferred from old foundation to new foundation of the house or property. In order to transfer the load from old foundation to new foundation a new pin or new dry sand –cement block is used. This is a very low cost method. This process of underpinning is most suitable for shallow foundation.
Mass Concrete Underpinning Method (Pit Method)
Mass concrete underpinning method is the most traditional method used for underpinning. This method used has been followed and implemented from centuries.Process of Mass Concrete Underpinning Method (Pit Method): The soil under the foundation is extended until it reaches a stable layer of soil or series of layer of rocks in the ground (Stratum).
The soil below the existing house foundation is dug/excavated in controlled conditions in different stages. In each stage pins are used. This process is continued till a stable layer of soil or stable strata is reached, then concrete is used to fill in the gap of the excavation performed. The concrete is left to dry and left for curing.
Curing plays an important role on strength development and durability of concrete. Curing takes place immediately after concrete placing and finishing, and involves maintenance of desired moisture and temperature conditions, both at depth and near the surface, for extended periods of time. Properly cured concrete has an adequate amount of moisture for continued hydration and development of strength, volume stability, resistance to freezing and thawing, and abrasion and scaling resistance.
The curing process involves which is most popular and most economical is water curing. It involves drying the cement and then watering the concrete once it dries. This helps us to retain the concrete floor for many years.
Mini Piled Underpinning
This method can be implemented where the loads from the foundation have to transferred to strata located at a distance greater than 5m. This method is adaptable for soil that has variable nature, access is restrictive and causes environmental pollution problems.
Piles of diameter between 150 to 300mm in diameter is driven which may be either augured or driven steel cased ones.
Pile Method of Underpinning
In this method, piles are driven on adjacent sides of the wall that supports the weak foundation. A needle or pin penetrates through the wall that is in turn connected to the piles as shown in figure-3.
These needles behave like pile caps. Settlement in soil due to water clogging or clayey nature can be treated by this method
Pre-test Method of Underpinning
It is employed for strip or pad foundation. Can be used for building with 5 to 10 stories. Here the subsoil is made compact and compressed, in the new excavation level that gives predetermined loads to the soil. This is done before underpinning is performed.<,/p>
Here reduced noise and disruption are expected. This method cannot be implemented for raft foundation.
Underpinning By Cantilever Needle Beam Method
Figure-2 represents the arrangement of cantilever pit method of underpinning, which is an extension of pit method. If the foundation has to be extended only to one side and the plan possess a stronger interior column, this method can be used for underpinning.
Advantages of Cantilever Needle Beam Method
Faster than traditional method
One side access only
High load carrying capability
Digging found uneconomical when existing foundation is deep
Constraint in access restricts the use of needle beams