Floor joists dovetailed into centre beam.

[charlieboy]

Having just lifted a couple of floorboards in a bedroom I have found that every other joist (1st 3rd 5th etc) has been dovetailed into the centre beam. The alternate joists(2nd 4th 6th etc) have just been slotted in as I would have expected. This only occurs in one of the bedrooms.
Was this normal practice in the 1700’s and if so, why would it have been done?
CB

 

[charlieboy]

This diagram might make it clearer. (or not!)

 

[malcolm]

It looks like the dovetails are intended to work in tension to tie the walls to the centre beam. I don't know if this was normal practice but it seems a good idea to tie the walls together halfway up the building and possibly their presence is an indication of good craftsmanship.

The tie would avoid bulging of the walls and if nothing else it should stop the floors from falling off when something like a rotten soleplate moves.

 

[Flyfisher]

I don't know about it being normal or regional practice, but I agree with Malcolm that it's a good idea for strong construction and I can support his point about such a design avoiding bulging walls fro experience.

In at least one of our bedrooms the 'king rafter' / A-frames (I'm not sure of exact terminology) connect to the wall plate with a dovetail joint. One of the joints had been severely damaged by years of water damage because of a leaking roof. The result was that the corner of the A-frame came apart and the wall began to splay outwards.

I would guess that this sort of attention to detail says something about the quality of the building and possibly the wealth of the original owner who commissioned it.

 

[88v8]

That's excellent.
And the alternate joists are recessed so as to provide support in compression.
Very good.

The joists in our kitchen ceiling have pulled so far out of their supporting beam that someone has had to add new joists alongside.

Ivor

 

[charlieboy]

Thanks for your thoughts on this.
I agree that the dovetails would tie the front and back walls together. Was it successful? Well the house is still standing, but the back wall is leaning out by about three or four inches at that height (so it may have had possibly some benefit).
This design might have "said something about the quality of the building and possibly the wealth of the original owner who commissioned it"
It is a pity that it says nothing about the wealth of the present owner!
CB

 

[Lime]

Having just lifted a couple of floorboards in a bedroom I have found that every other joist (1st 3rd 5th etc) has been dovetailed into the centre beam. The alternate joists(2nd 4th 6th etc) have just been slotted in as I would have expected. This only occurs in one of the bedrooms.
Was this normal practice in the 1700’s and if so, why would it have been done?
CB

The floor looks to have been designed and constructed very well.