Questions relating to removal of load bearing wall

[pasty-man]

I have obtained specifications and calcs from a chartered structural engineer with regard to removing a downstairs internal wall in my 200 year old random stone built cottage.
The spec defines a steel box frame of 152mm rsj's with the verticals (which are to be installed 'chased' back into the walls either side) tied into the walls with type 2 ties - ancon spb or similar. The rsj on the floor finishing with its upper surface 50mm from floor level.
Hope you get the picture.

I asked him for suggestions as to how we get these type 2 wall ties fixed into the stonework/mortar and he confessed it would be awkward but we should do our best to fix them with mortar into cavities made between the stones.
Fiddly is not the word when this is working in a 'chased 'section of stone wall.
Has anyone got any suggestions here??
Wall construction is random stone with a rubble/'muddy' filled cavity. Walls about 2 ft or so thick.

Next one - What is the appropriate method to create/ finish the 'hole' for the rsj along below floor level, with regard to creating a base, damp proofing etc.
I believe the house has no foundations as such although the floor is a poured concrete/screed finish.


I thank anyone in advance for their input here and will reply to posts as quickly as family life allows!

 

[Shytalkz]

Hope you get the picture.

Funnily enough, it's called a picture frame .

What's its purpose (don't say supporting something above it!), as I'm struggling with the need for partially chasing-in to the wall at the moment, or what that achieves.

 

[pasty-man]

Its the removal of a supporting wall. A steel frame is to be installed (4 steels).
The chasing of the walls is to recess the 2 vertical beams so not to protrude into the room.

 

[Shytalkz]

So it's in the plane of the wall, but chased into the sides of the opening?

 

[chessspy]

These rubble filled random stone walls are so different to modern construction, that your CSE is clearly not up to speed on this sort of thing.
You/one, cannot simply 'add on' a standard construction solution to such a problem.
sack him, get your money back, and employ an SE who understands the problems associated with altering a rubble [filled] wall building in such a fundamental way.

 

[pasty-man]

Shytalks - The two vertical steels are to be 'set back' into the inner skins of (and 'tied' to) two external walls. This is so they do not 'intrude' into the room. The horizontal upper steel sits below a joist supporting it, the wall above etc etc and is bolted to the two verticals. The lower horizontal steel sits just below floor level and again is bolted to the verticals.

chessspy - I understand and appreciate what you are saying however the SE has given good reason for this design in saying that we dont want to tie this structure to foundations (As the rest of the house isn't). The stone walls would not safely be capable of supporting an rsj & padstone design etc..
His given reasoning seems very logical to me. The only aspect I question is tying this to the walls.
At this moment I do not have enough knowledge to be able to challenge this specification.

Do you have any thoughts on this that I could confront him with. I would appreciate advise if you are experienced in the type of stone wall cottage construction that I have.

 

[chessspy]

Hi, pasty,
yes, I have renovated the oldest cottages in Northern Europe, and also renovated a similar build in Beverley in yorkshire.
That building was on mass chalk founds of a size I couldn't fathom, when I did a test dig.
Have you done a test to see if your suppositions on the founds, or possible lack of same are accurate?
I would suggest that you do a bit of digging, as the superstructure your surveyor is proposing should be based on fact not guesswork

 

[pasty-man]

There has been no investigatory dig at this time. I/se are simply basing assumptions on age of property. The house exhibits no evidence of a problem with the foundations or lack of. The whole building moves as one with no detrimental evidence to suggest a varying density to its founds. After all its over 2 centuries old!
Can you please expand on your reasons for questioning in this line. The proposed solution from my viewpoint practically negates the question of the quality or lack of foundations as the load is spread across a horizontal steel at ground level. The load is distributed(allegedly) effectively with the steel onto the ground.
What would you propose based on possible outcomes?
I thank you for your valued input as you are clearly highly experienced in this field.

 

[chessspy]

actually Pasty, I think I'm out of my depth here, so I'll but out.
good luck with the build.

 

[Shytalkz]

Picture frames help to maintain the existing foundation loading profile, by spreading the load from above along the bottom beam. However, this theory is somewhat negated if the existing foundation has to be removed to install the frame: you still end up with a stiffer section of foundation in comparison to the foundations on either side.

That said, it retains the advantage of not putting concentrated loads on a wall of questionable load-bearing ability, so I can fully understand the approach taken.

With regard to tying-in, as you have correctly identified, trying to install a rigid tie into random walling is not without its problems. But anything that you can achieve is better than nothing.

I would suggest using Helibar, drilled and resin-bonded into the wall wherever you can and at close vertical centres, leaving a fair length sticking out from the reveal, which can be hand bent around the flange/s of the post. Not pretty, but it will all be hidden up by the boxing-in and will provide a degree of restraint to the wall.

 

[pasty-man]

Shy - I like your thinking!!
Can you make any suggestions for dealing with the floor 'trench' with regard
to a base before placing the steel in & prevention of damp etc.