Connection of Timber Floor to Old Rubble masonry wall.

[Contraflexure74]

Hi,

I was wondering if anyone had an opinion on a good detail of how to connect a new timber floor to an old rubble masonry wall. Basically the 1st and second floors are being removed and replaced in an old house. The external walls are 600mm thick. I was going to create a series of concrete pockets along the old wall and fill with 35N concrete (300x300mm). Then bolt a treated 5x2 timber with fixings at the pocket locations to the wall. I was then going to fix joist hangers from the 5x2 to support the floor joists. Anyone got a better idea?

Or should I think about bolting a channel section to the wall and sit the floor joists on the bottom flange of the channel section.

I guess I will need to provide pockets on the parallel walls also so I can tie strapping across the joists to these walls?

J.

 

[robyengIT]

some suggestions

 

[Canuck65]

How are the interior faces of the rubble stone walls being constructed/finished? If they are to be finished with drywall, one could construct an interior 2x4 load bearing wall on the interior face of the rubble stone walls, then just platform frame from there. If you are in a cold climate, the 2x4 cavity could then be spray foam insulated on the interior face to provide R-value and a barrier to air flow. I have 750mm to 900mm thick field stone walls at my house and it is amazing how much air still passes through that thickness of stone on a windy day.

 

[jayrod12]

Canuck, you're assuming that there is a wide enough footing below the rubble wall (which in my experience is not always the case).

I would say the OP has a good handle on a reasonable way to do it. I have, on occasion, seen epoxy anchors used directly into the stones, but that required numerous anchors to keep the load in each one quite low.

 

[dhengr]

JohnFitzgerald74:
The difficulty of your problem is that you and the contractor have to really evaluate the existing ruble stone wall in minute detail. If not, every individual connector will not be worth its cost, let alone the installation effort. You have to be fairly conservative in assigning strength to each connector, as a function of how every time you touch one brick or stone, you loosen the next three adjacent bricks or stones. In a grosse way, the wall is certainly capable of carrying the distributed loading of a new floor, or whatever, but if the brick or stone below the next new connector ends up loose because of your drilling action, or whatever, that connector is essentially worthless. Look back at the old details where each joist was fire cut and set into a pocket in the wall. If old joist/beam pockets could be used without disturbing the masonry, so much the better. While this may be some added work to accomplish, it is redundant, and most of the work can be hidden within the floor structure depth. Can you repoint and strengthen the wall at the immediate elevation of the new work. Those walls have supported that structure for hundreds of years and yet, the minute you start to disturb them, they just start to crumble, and there is no end, they just keep crumbling three stones in front of your work. With today’s diamond saws you can cut and chip fairly nice pockets in a masonry wall, assuming that the wall stays together during this process.

 

[Guastavino]

So most manufacturers will do on-site load testing for you of the epoxy anchors. And if you know them, they will likely do it free if you spec their product. I recently asked Powers if they would do testing if I was only going to be specifying about (4) total anchors (small job). They were like, sure thing! So I would recommend you call your local rep.

It's good for their business to provide this service to engineers. Gives them face time with engineers and they hope we remember that on the big jobs. And, if they have a good product, I will.

 

[Contraflexure74]

Thanks Engineers for all your responses, some good advice there.

J.

 

[Teguci]

I would think drilling and epoxying in a ledger beam would make the most sense with an appropriate anchor testing program. I would think cutting in pockets would add to potential problems. If shear on the face of the wall turns out to be a problem you could always put the anchors in at an upward angle, but usually the face shell is the good stuff.