Following on from;
http://www.somersoft.com/forums/showthread.php?t=66902
I now present the engineers report. All looks a little too much for me to go through. What is the consensus? Cheers
This report has been solely prepared to provide an engineering assessment into the possible causes of slab cracking and movement of the southern end of the house.
Description of Site
The house is located on the corner of xxxxx. It is a brick veneer construction with sheet roof. The house is L shaped house in plan view with with the wider part of the house oriented towards the street frontage. The house is built on a cut fill platform with the southern end of the house built on a fill platform. The amount of fill in this corner of the block is estimated to be in the order of 200 to 300 mm.
The site is generally well drained. There are garden beds around the house with low to medium height shrubs in stone beds on the eastern side of the house. There is a stone garden bed on the western side of the house running full length of the house and returns around the southern side of the house. All roof water is collected and discharged to in ground bubblers in the yard or tank.
Comments from Investigation
The following was noted from the investigation:
1. A crack is visible on the internal wall between the dining area and the study. The crack
propagates from the top right-hand corner of the door frame (as seen from the dining area) to the right at 45 degrees. The crack width is approximately 2mm at the widest point near the door to nothing near the cornice. The door frame is visible skewed to the left at the top of the frame.
2. The cornice further along the same wall in the kitchen showed signs of movement. The cornice has partially detached in some parts of the wall at the top and bottom of the cornice. The damage coincided with the location of the joinery in the kitchen where there is a bulkhead built over the cupboards resulting in a section of wall that would not be as stiff as a full height wall.
3. The wall between the back entertainment area and study has areas where the plaster tape in the corner between the intersecting walls has moved. This has deformed and delaminated from the wall slightly.
4. A 1mm crack was visible in the ceiling in the hallway between the kitchen area and the hallway to the garage. The crack runs in a north / south orientation. And approximately 1500 in length.
5. The tiled floor in the kitchen dining area did not have any signs of cracking or hollowness at the time of the inspection.
6. There was no perceptible level change in the tiles throughout the dining / kitchen area.
7. There was a gap of 1 – 1.5mm between the internal wall in between the lounge and dining area and the tiles on the floor. There was no hollowness of the tiles in this area at the time of the inspection.
8. Some cracking was visible in the brick veneer on the western wall. Cracks generally propagate from the corners of the windows along this wall and are approximately 1-2.5mm in width.
9. Some cracking was noticed adjacent the saw cut joints in the external slabs at the front and eastern side of the house. These were generally 0.5mm to 1mm in width.
10. The gravel garden on the western wall did have some low points and showed some signs that water does pond in spots during rain events.
11. There were no signs of unexpected cracking of the external slabs at the time of the inspection.
12. There is a lateral displacement of the brick veneer in the SW corner of the house. This is at the damp coursing level and appears to have been built in this manner.
13. Apart from the door into the study (internal sliding door) all doors and windows moved freely.
14. Discussions with x recalled that the deformation of the plasterboard tape at the wall intersection (as noted above) was present for some time; however the damage to the internal wall between the study and dining areas was unknown.
AS2870 Residential Slabs and Footings Code
Appendix C of AS2870-1996 Residential Slabs and Footing Construction classifies damage to structures due to foundation movement.
The slab would be classified as Damage Category 0 with approx crack widths <0.3mm and a change in offset from a 3m straight edge <8mm. This category has insignificant movement of the slab from level and does not need repair.
The walls would be classified as Damage Category 1 and 2 with Category 2 being cracks up to <5mm in width. These cracks are described in the standard as noticeable but easily filled. Doors and windows stick slightly.
The masonry veneer on the house has minor cracks in weak points at the corners of windows, but generally the expansion joints appear to be performing within their limits at this stage. The masonry would generally be classified as Damage Category 2 with cracks generally below 5mm which do not warrant repair in accordance with the code. The openings in a masonry veneer structure are generally used to allow for movement within the slab to avoid cracking in the masonry. These are called control joints which control where movement can occur within a structure. Clause 4.8.2 of AS3700 Masonry Structures generally only allows for opening movement of control joints in the order of 10mm. The movement experienced does not exceed this recommendation.
Conclusions
Overall the extent of cracking appears to be limited at the time of the inspection to the south western corner of the house. The cracks are 2mm at worst and occur generally in the same alignment from the study across the house near the dining area. The majority of the visible damage is internal and located on the wall between the back room and the dining area. Some cracking had occurred in the veneer at the weak point in the wall next to a window in the bedroom next to the study, but this was minor.
From the discussions with Mr X, it is possible that settlement of this end of the house has been occurring for some time. The corner tape may move without notice more than a sraight section of plasterboard wall as the movement is taken up in the deformation of the tape.
Based on the findings of the investigation, it is concluded that the house has experience some settlement of the southern end of the house at this location. As this part of the house is founded on fill material, it is most likely that the settlement is as a result of that fill consolidating (compacting) over time.
Recommendations
It is recommended that following be undertaken:
Undertake a longer term monitoring program to assess the current state of damage and
determine whether movement is still occurring. As the house is built on reactive soils, it is
possible that some foundation movement may continue to occur due to seasonal changes in soil moisture content. Monitoring need only require measurement of the width of the opening in the SE corner of the house ever 6 to 12 months. Current measurements as at May 2010 are 2mm.
Look at the site drainage and where necessary slope the ground away from the house to ensure that the site is free draining. Remove and avoid any areas where water can potentially pond. Maintaining constant soil moisture content is important.
Maintain a minimum clearance of the sewerage treatment sprinklers at least 8m from the
house.
All owners should become aware of their responsibilities to care for and adequate maintain a reactive clay site (particularly with on site sewerage and stormwater disposal). Guidance is given in a CSIRO information sheet which is available to homeowners entitled ‘Guide to Home Owners on Foundation Maintenance and Footing Performance’ (Obtainable from the Publications Office of Division of Building Construction and Engineering, PO Box 56 Highett, Victoria, 3190.) Should the cracking continue and increase to greater than 5mm it is recommended that further investigation into whether foundation underpinning may be warranted.
http://www.somersoft.com/forums/showthread.php?t=66902
I now present the engineers report. All looks a little too much for me to go through. What is the consensus? Cheers
This report has been solely prepared to provide an engineering assessment into the possible causes of slab cracking and movement of the southern end of the house.
Description of Site
The house is located on the corner of xxxxx. It is a brick veneer construction with sheet roof. The house is L shaped house in plan view with with the wider part of the house oriented towards the street frontage. The house is built on a cut fill platform with the southern end of the house built on a fill platform. The amount of fill in this corner of the block is estimated to be in the order of 200 to 300 mm.
The site is generally well drained. There are garden beds around the house with low to medium height shrubs in stone beds on the eastern side of the house. There is a stone garden bed on the western side of the house running full length of the house and returns around the southern side of the house. All roof water is collected and discharged to in ground bubblers in the yard or tank.
Comments from Investigation
The following was noted from the investigation:
1. A crack is visible on the internal wall between the dining area and the study. The crack
propagates from the top right-hand corner of the door frame (as seen from the dining area) to the right at 45 degrees. The crack width is approximately 2mm at the widest point near the door to nothing near the cornice. The door frame is visible skewed to the left at the top of the frame.
2. The cornice further along the same wall in the kitchen showed signs of movement. The cornice has partially detached in some parts of the wall at the top and bottom of the cornice. The damage coincided with the location of the joinery in the kitchen where there is a bulkhead built over the cupboards resulting in a section of wall that would not be as stiff as a full height wall.
3. The wall between the back entertainment area and study has areas where the plaster tape in the corner between the intersecting walls has moved. This has deformed and delaminated from the wall slightly.
4. A 1mm crack was visible in the ceiling in the hallway between the kitchen area and the hallway to the garage. The crack runs in a north / south orientation. And approximately 1500 in length.
5. The tiled floor in the kitchen dining area did not have any signs of cracking or hollowness at the time of the inspection.
6. There was no perceptible level change in the tiles throughout the dining / kitchen area.
7. There was a gap of 1 – 1.5mm between the internal wall in between the lounge and dining area and the tiles on the floor. There was no hollowness of the tiles in this area at the time of the inspection.
8. Some cracking was visible in the brick veneer on the western wall. Cracks generally propagate from the corners of the windows along this wall and are approximately 1-2.5mm in width.
9. Some cracking was noticed adjacent the saw cut joints in the external slabs at the front and eastern side of the house. These were generally 0.5mm to 1mm in width.
10. The gravel garden on the western wall did have some low points and showed some signs that water does pond in spots during rain events.
11. There were no signs of unexpected cracking of the external slabs at the time of the inspection.
12. There is a lateral displacement of the brick veneer in the SW corner of the house. This is at the damp coursing level and appears to have been built in this manner.
13. Apart from the door into the study (internal sliding door) all doors and windows moved freely.
14. Discussions with x recalled that the deformation of the plasterboard tape at the wall intersection (as noted above) was present for some time; however the damage to the internal wall between the study and dining areas was unknown.
AS2870 Residential Slabs and Footings Code
Appendix C of AS2870-1996 Residential Slabs and Footing Construction classifies damage to structures due to foundation movement.
The slab would be classified as Damage Category 0 with approx crack widths <0.3mm and a change in offset from a 3m straight edge <8mm. This category has insignificant movement of the slab from level and does not need repair.
The walls would be classified as Damage Category 1 and 2 with Category 2 being cracks up to <5mm in width. These cracks are described in the standard as noticeable but easily filled. Doors and windows stick slightly.
The masonry veneer on the house has minor cracks in weak points at the corners of windows, but generally the expansion joints appear to be performing within their limits at this stage. The masonry would generally be classified as Damage Category 2 with cracks generally below 5mm which do not warrant repair in accordance with the code. The openings in a masonry veneer structure are generally used to allow for movement within the slab to avoid cracking in the masonry. These are called control joints which control where movement can occur within a structure. Clause 4.8.2 of AS3700 Masonry Structures generally only allows for opening movement of control joints in the order of 10mm. The movement experienced does not exceed this recommendation.
Conclusions
Overall the extent of cracking appears to be limited at the time of the inspection to the south western corner of the house. The cracks are 2mm at worst and occur generally in the same alignment from the study across the house near the dining area. The majority of the visible damage is internal and located on the wall between the back room and the dining area. Some cracking had occurred in the veneer at the weak point in the wall next to a window in the bedroom next to the study, but this was minor.
From the discussions with Mr X, it is possible that settlement of this end of the house has been occurring for some time. The corner tape may move without notice more than a sraight section of plasterboard wall as the movement is taken up in the deformation of the tape.
Based on the findings of the investigation, it is concluded that the house has experience some settlement of the southern end of the house at this location. As this part of the house is founded on fill material, it is most likely that the settlement is as a result of that fill consolidating (compacting) over time.
Recommendations
It is recommended that following be undertaken:
Undertake a longer term monitoring program to assess the current state of damage and
determine whether movement is still occurring. As the house is built on reactive soils, it is
possible that some foundation movement may continue to occur due to seasonal changes in soil moisture content. Monitoring need only require measurement of the width of the opening in the SE corner of the house ever 6 to 12 months. Current measurements as at May 2010 are 2mm.
Look at the site drainage and where necessary slope the ground away from the house to ensure that the site is free draining. Remove and avoid any areas where water can potentially pond. Maintaining constant soil moisture content is important.
Maintain a minimum clearance of the sewerage treatment sprinklers at least 8m from the
house.
All owners should become aware of their responsibilities to care for and adequate maintain a reactive clay site (particularly with on site sewerage and stormwater disposal). Guidance is given in a CSIRO information sheet which is available to homeowners entitled ‘Guide to Home Owners on Foundation Maintenance and Footing Performance’ (Obtainable from the Publications Office of Division of Building Construction and Engineering, PO Box 56 Highett, Victoria, 3190.) Should the cracking continue and increase to greater than 5mm it is recommended that further investigation into whether foundation underpinning may be warranted.
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