Placing Fill embankment on Bldg Firewall??? 2

[mick0]

hi All, hope everyone is well and happy holidays! I need a recommendation for a scenario i have, here it goes: There is a vacant lot wherein there are Firewalled (masonry wall with columns every 10 feet)buildings to the left and right side of it. both of the firewalled buildings' finish floor elevations are 3 feet above the original ground. the vacant lot is 30 feet wide. there is a plan to build a building on the vacant lot 18 feet wide with 6 feet setback on both the left and right side. the existing ground is to be raised 3 feet to match the firewalled buildings' elevations. the question is do you still need to construct a retaining wall right next to the firewalled buildings? or is the volume of dirt to be raised does not affect the firewalled buildings? my thought is i just think of it as if the firewall just gets sandwiched between their side and the new dirt to be added on the vacant lot and thus does not affect the neighboring buildings, but i need some expert opinion. i hope i explained it clear enough. comments and suggestions are appreciated. thanks

 

[rowingengineer]

mick0,
You need to check with your local council because if the next-door neighbour decides to demolish the firewall what happens to your property, probably not a big deal but it is good to know te council stand point, normally they would consider the FFL to be the Ground level.

However from a structural point of view it would be fine, however I would keep it 150mm below the FFL of the building to ensure water proofing. I would also ensure water can’t pound against the firewall.



Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[mick0]

Hi rowingengineer, thanks for the quick response. Yes its a good idea to be a bit lower than the neifhbors' finish floor. I am intending to plaster the firewall to waterproof it before filling in the dirt. So from a structural standpoint, that volume of fill will not compromise the stability of the wall right? Im assuming that the lateral pressure to the wall due to the fill dirt will be negligible? Thanks

 

[rowingengineer]

Micko,
lateral pressure to the wall due to the fill dirt will be negligible? No, it isn't, if the wall is a basement wall ect. it all depends on situation, as for a fire wall for a single story residence with a slab on ground it shouldn't be a problem. However i would recommend installing subsoil drains next to the wall and ensure good drainage away from the wall.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[cvg]

you will need to get permission from the neighboring building owners and if it was me I would not allow what you are proposing. You will need to get a grading permit to do this and I would also be surprised if the city allowed it. Also, are you sure that your property line is at the edge of the existing buildings? Most cities require setbacks and zero lot lines are an exception to this.

 

[Ron]

Based on your sketch, it appears that there is only a stemwall for the adjacent foundation, with the interior filled with soil. If that's the case, your fill has little or no effect on the walls, firewall or not.

The spacing between the buildings might require a different fire rating on their walls. Check on that.

 

[mick0]

i forgot to mention, the neighbor to the left (facing the lot, see image 3) is a 2 story house, the one on the right (under construction, see image 2) is also going to be 2 story. both of them are slab on ground, is that still ok? i am attaching the pics of the site. we are proposing a 2 story house also. this is going to be built in asia, but i will not be there when it gets constructed so i want to make sure that it can be done. thanks again to all for your valuable inputs.

 

[mick0]

here is the second pic

 

[mick0]

and the 3rd pic, this is the 2 story house to the left of the site

 

[Ron]

mick0...it looks like you'll only be equalizating the pressure against the stemwalls...not an issue.

Again, check the fire rating. In general, if you have such small spacing between buildings, the exterior wall must carry additional fire rating.