As Mike has mentioned previously, most existing brick cross walls or spine walls provide a support to the flank or front/rear walls. However, the entire wall is typically removed with just a beam inserted in place on small returns or onto the spine wall and flank wall etc. No appraisal is done for the existing foundations (or very rarely). I recall seeing something in CP 111 or Ciria report 111 (Structural Renovations of existing buildings), that if loading on the existing walls is increased by circa 10% then the foundations might be overstressed. However, large openings or entire walls are removed and replaced with a beam with much higher concentrated loads or as you mention small piers with much higher loads at the bottom. When I do the calcs are check the foundations considering a corbelled foundation, the numbers say it doesn't work. I typically like putting in SHS posts with small offset foundations doweled into the existing foundations if possible. Then the posts are strapped back to the wall. However, many clients do not like the costs associated as they say they have seen just beams used on youtube. It is quite frustrating.
Thank you for sharing your knowledge & highlighting these crucial considerations. We agree that it is imperative to evaluate the load-bearing capacity of existing foundations prior to adding additional loads through the removal of walls and replacement with beams. Your recommendation to use SHS posts with small offset foundations doweled into the existing foundations is a practical solution, as it offers increased stability & support. While we understand that the costs associated with these measures may not always be favored, it is vital to prioritize safety & structural integrity. We appreciate your valuable insights & expertise.
Thanks for the video; very helpful. It does raise one issue that puzzles me. You mention the additional load on the existing foundations which may be more than they can cope with. It is very common in domestic situations for a “knock through” to be carried out involving the removal of part of a loadbearing wall; A typical case would be say a 2.5m gap being created with piers of 0.5m either side. This would significantly increase the load on each pier partly offset by the triangulation of the brickwork below floor level. As I understand it the only way to check this out would be by a physical inspection of the foundations and soil beneath the lowest part of the foundation. This, in my (very) limited experience is never done. I suspect nobody thinks about it and Building Control do not raise it as an issue. The inspection would be very disruptive. However, I have never heard about it subsequently being an issue. Many domestic “knock throughs” are done without the proper approvals and expert input. I suppose one could conclude that because there are never any problems the existing foundations can be assumed to be more than adequate to take the additional load. There must be an element of risk, however. One other query I have relates to the piers that are left and the restraint that they provide to the external wall. Is there a minimum width to the pier or can it be removed entirely? Then the removed wall is no longer restraining the external wall and there is a risk of it bulging outwards especially if the floor joists do not bear onto it as would be normal and there is no other restraint provided. I am trying to understand all the relevant issues and your videos have been very helpful so thanks again.
Thank you for your comment & for raising these important points. You're right that it is very common for "knock through" renovations to involve the removal of part of a loadbearing wall, which can significantly increase the load on the foundations and piers. You're also correct that the only way to know for sure if the existing foundations can cope with the additional load is by physically inspecting the foundations & soil beneath the lowest part of the foundation. This can be disruptive and is not always done, but it is important to consider the potential risks involved in not properly assessing the load bearing capacity of the foundations. As for the piers that are left after a "knock through," it is generally recommended that they be at least a min width to provide sufficient restraint to the external wall. The min width will depend on the specific circumstances of the building & the load that the piers are expected to bear. It is generally not recommended to remove the piers entirely, as this can lead to bulging of the external wall if there is no other restraint provided. I hope this helps clarify things for you. Thank you again for your comment & for watching the videos. If you have any further questions, please don't hesitate to ask!
Thank you for your comment. We use our spare time to create these videos, we aim to upload frequently however we find ourselves frequently overwhelmed with projects. thank you for your support and please stay tuned :)
On point as always SECalcs 👌
Glad to hear Emma :)
As Mike has mentioned previously, most existing brick cross walls or spine walls provide a support to the flank or front/rear walls. However, the entire wall is typically removed with just a beam inserted in place on small returns or onto the spine wall and flank wall etc. No appraisal is done for the existing foundations (or very rarely).
I recall seeing something in CP 111 or Ciria report 111 (Structural Renovations of existing buildings), that if loading on the existing walls is increased by circa 10% then the foundations might be overstressed. However, large openings or entire walls are removed and replaced with a beam with much higher concentrated loads or as you mention small piers with much higher loads at the bottom. When I do the calcs are check the foundations considering a corbelled foundation, the numbers say it doesn't work.
I typically like putting in SHS posts with small offset foundations doweled into the existing foundations if possible. Then the posts are strapped back to the wall. However, many clients do not like the costs associated as they say they have seen just beams used on youtube. It is quite frustrating.
Thank you for sharing your knowledge & highlighting these crucial considerations. We agree that it is imperative to evaluate the load-bearing capacity of existing foundations prior to adding additional loads through the removal of walls and replacement with beams. Your recommendation to use SHS posts with small offset foundations doweled into the existing foundations is a practical solution, as it offers increased stability & support. While we understand that the costs associated with these measures may not always be favored, it is vital to prioritize safety & structural integrity. We appreciate your valuable insights & expertise.
Thanks for the video; very helpful. It does raise one issue that puzzles me. You mention the additional load on the existing foundations which may be more than they can cope with. It is very common in domestic situations for a “knock through” to be carried out involving the removal of part of a loadbearing wall; A typical case would be say a 2.5m gap being created with piers of 0.5m either side. This would significantly increase the load on each pier partly offset by the triangulation of the brickwork below floor level.
As I understand it the only way to check this out would be by a physical inspection of the foundations and soil beneath the lowest part of the foundation. This, in my (very) limited experience is never done. I suspect nobody thinks about it and Building Control do not raise it as an issue. The inspection would be very disruptive. However, I have never heard about it subsequently being an issue. Many domestic “knock throughs” are done without the proper approvals and expert input.
I suppose one could conclude that because there are never any problems the existing foundations can be assumed to be more than adequate to take the additional load. There must be an element of risk, however.
One other query I have relates to the piers that are left and the restraint that they provide to the external wall. Is there a minimum width to the pier or can it be removed entirely? Then the removed wall is no longer restraining the external wall and there is a risk of it bulging outwards especially if the floor joists do not bear onto it as would be normal and there is no other restraint provided.
I am trying to understand all the relevant issues and your videos have been very helpful so thanks again.
Thank you for your comment & for raising these important points. You're right that it is very common for "knock through" renovations to involve the removal of part of a loadbearing wall, which can significantly increase the load on the foundations and piers.
You're also correct that the only way to know for sure if the existing foundations can cope with the additional load is by physically inspecting the foundations & soil beneath the lowest part of the foundation. This can be disruptive and is not always done, but it is important to consider the potential risks involved in not properly assessing the load bearing capacity of the foundations.
As for the piers that are left after a "knock through," it is generally recommended that they be at least a min width to provide sufficient restraint to the external wall. The min width will depend on the specific circumstances of the building & the load that the piers are expected to bear. It is generally not recommended to remove the piers entirely, as this can lead to bulging of the external wall if there is no other restraint provided.
I hope this helps clarify things for you. Thank you again for your comment & for watching the videos. If you have any further questions, please don't hesitate to ask!
do a vid on designing ply to act as a diaphram
Thanks for the video! Could you kindly reference this material to a literature please. I would like to get a book on this subject if possible.
Where were you? You have uploaded the video after long time
Thank you for your comment. We use our spare time to create these videos, we aim to upload frequently however we find ourselves frequently overwhelmed with projects.
thank you for your support and please stay tuned :)