The first floor level of my late 19th century property has its floor joists set straight into the solid 9 inch brickwork wall i.e. 4x2 timber joists sitting in 6x2 holes in the brickwork to a depth of about 2 inches. The 6 inch height of the holes means you can see the top face of the 4 inch joists sitting in the wall and a number of these joists whilst perfectly sound along their length have rotted in the holes. I propose acro propping the joists from below, cutting out the rot and a bit more, say 1ft or so and joining in new sections of joist. Can anybody suggest the best way of joining the old and the new joists end to end? Are there purpose made metal plates that can hold the joists together with those large screw bolts? I don’t want to fix new joists along side the old as I want to align the new timber with the existing brickwork holes. One other problem, the ground floor lath plaster ceiling is fixed to the underside of these joists. I guess I'll have to loose a bit of this where the joists get cut out?
- Thread starter michael
- Start date
Penners
Member
- Messages
- 17,294
- Location
- Suffolk, England
Here'sa a scarfing joint that I've used in the past for a similar application. It worked well.
Thanks Mark, Good idea
Fill up the holes with brick and install joist hangers. I’ve never used these before, How are they fixed? The wall I’m fixing to is 190 years old (soft brick) so I don’t fancy drilling great big holes into it. If they are simply fixed by setting a plate into the wall with mortar then I would want to use hydrated (non hydraulic lime) would there be a strength issue here? Lastly would the joist hangers prevent me from re fixing my laths on the underside of the joist?
Penners, you’re idea also looks good but difficult for me. I’m not a carpenter and the area I have to work in (between floorboards, under insitu wooden benches on a first floor balcony whilst the good part of the joist is still in place) is very restricted.
Fill up the holes with brick and install joist hangers. I’ve never used these before, How are they fixed? The wall I’m fixing to is 190 years old (soft brick) so I don’t fancy drilling great big holes into it. If they are simply fixed by setting a plate into the wall with mortar then I would want to use hydrated (non hydraulic lime) would there be a strength issue here? Lastly would the joist hangers prevent me from re fixing my laths on the underside of the joist?
Penners, you’re idea also looks good but difficult for me. I’m not a carpenter and the area I have to work in (between floorboards, under insitu wooden benches on a first floor balcony whilst the good part of the joist is still in place) is very restricted.
CHRIS
Member
- Messages
- 421
- Location
- ESSEX MATE!
You could use Timber to Masonry hangers and chase out the lime and replace like for like, or you could also bolt a ledger along the length of the wall in PT timber and use face fix hangers with nails or screws (my choice).
http://www.orbitalfasteners.co.uk/product_detail.php?id=3499
You could bolt another joist next to the existing one if the original one does not fit the hanger.
http://www.orbitalfasteners.co.uk/product_detail.php?id=3499
You could bolt another joist next to the existing one if the original one does not fit the hanger.
chuckey
Member
- Messages
- 883
- Location
- wenslydale
You don''t say if the floor boards are still fixed to the joists! Joist hangers are meant to be fitted tight to the wall and the joist sitting in them with a with gap of less then 6mm. The normal way is to drop the joist in them from the top, difficult if the boards are still fitted. They also come in standard "metric" sizes, which means that it is unlikely that old joists will fit neatly in them. Sorry to rain on your parade, but these are some of the problems I have come across. I have researched the web for joist hangers and have found one sort (common in the UK) that requires fixing with SQUARE shanked 1 3/4" nails - where does one find these?
Unless the length of the joists are very short, 4 X2 " are too small for floor joists, the floor will bounce too much and your ornaments will rattle.
Hangers are also rated for the "softness" of the surface on which they are too be fitted, celcon blocks, bricks, concrete blocks, it is unlikely that in a domestic situation that it would effect you, but I think that lime bedding is a softness too far. I would fix them dry with blue slate packing and a wodge of some thing like gripfix to stop any rattling, extra shimming could be got from galvanised fixing plates.
I have been contemplating marketing some demountable joist hangers for situations just like this but life is too hectic at present to take the project further.
Frank
Unless the length of the joists are very short, 4 X2 " are too small for floor joists, the floor will bounce too much and your ornaments will rattle.
Hangers are also rated for the "softness" of the surface on which they are too be fitted, celcon blocks, bricks, concrete blocks, it is unlikely that in a domestic situation that it would effect you, but I think that lime bedding is a softness too far. I would fix them dry with blue slate packing and a wodge of some thing like gripfix to stop any rattling, extra shimming could be got from galvanised fixing plates.
I have been contemplating marketing some demountable joist hangers for situations just like this but life is too hectic at present to take the project further.
Frank
If you cant do the joint Penners demonstrated, a simple angled cut is also an option, ie as the one above but without the backtracking ends to the cut. Its also poss to insert stubs into the wall or hangers and join them to the remaining old joist with sidepieces. If youre using side peices, a simple square butt joint also works.
As for 2x4, its plenty for a 12' room, as long as you dont mind typical creaky PP standards. Not much sound insulation too, but thats how many such houses are.
Murders have been committed over neighbourly noise, so who knows what the result of your 2x4s could be.
A few little additions can really help stiffen a floor up.
http://www.wiki.diyfaq.org.uk/index.php?title=Strengthen_a_Wood_Floor
NT
As for 2x4, its plenty for a 12' room, as long as you dont mind typical creaky PP standards. Not much sound insulation too, but thats how many such houses are.
Murders have been committed over neighbourly noise, so who knows what the result of your 2x4s could be.
A few little additions can really help stiffen a floor up.
http://www.wiki.diyfaq.org.uk/index.php?title=Strengthen_a_Wood_Floor
NT
Thanks all for your comments.
Rightly or wrongly, I’ve come to the conclusion that may be the best way to undertake the repair without disturbing the brickwork is to cut the rotten pieces of joist out by say 1ft back from the retaining holes in the wall. Replace with new pieces of joist butted up to the old end on end and then coach bolt a secondary piece of joist of the same size along side the new and old with two coach bolts either side of the join.
Rightly or wrongly, I’ve come to the conclusion that may be the best way to undertake the repair without disturbing the brickwork is to cut the rotten pieces of joist out by say 1ft back from the retaining holes in the wall. Replace with new pieces of joist butted up to the old end on end and then coach bolt a secondary piece of joist of the same size along side the new and old with two coach bolts either side of the join.