Replacing a suspended floor in Victorian house

[Matt K]

Hi, sorry for the long post! Just thought I'd get as much info in as possible!

I'm renovating a Victorian terraced house in South London. I'm turning an old bedroom into a bathroom, having finished the work on the roof (which was falling down), I'm now ready to start the work in the actual room, which is at the top of the outrigger part of the house at the back. I've put some pictures/drawings together to help explain my questions, here's where the room is in the house:
www.matt-k.com/downloads/house/bathroom/floor/overview_of_house.png

I noticed that the floor was bouncing a bit so asked a builder friend if he could come in and take a look, he recommended that I install noggins to support the floor and stop "lateral torsion", which I did as per the pic below, as you can see I stripped the ceiling out from underneath the floor - it was asbestos and needed to come out anyway) so have access above and below.
www.matt-k.com/downloads/house/bathroom/floor/noggins.jpg

Problem is, having installed the noggins it's still bouncing quite a lot! As I want to install water UFH I'd really like to minimise it as much as possible. I think that it's the timbers being over 120 years old (they've done well considering!) is the issue, as it's not bouncing at the ends near the wall, only in the middle, and I can actually see the joists bending from underneath when someone jumps in the room above.

While doing the noggins I also noticed another potential issue, in that the header plate the joists sit on (not sure if that's the correct name!) on the partition wall side of the room... seems to be coming away from the wall. Also there's a stud wall in the room below and the header plate seems to rise up to it either side, as though the stud wall is supporting some of the weight of the floor above. It's not easy to see from the pics but I've taken some to try to illustrate what I mean:
www.matt-k.com/downloads/house/bathroom/floor/header_coming_away.jpg
www.matt-k.com/downloads/house/bathroom/floor/dodgy_header.jpg

I'm thinking that probably the best course of action would be to replace the floor, especially while I have it all open and access to it etc. With that in mind my plan is to:

1. Temporarily reroute the pipework currently in the floor (most is old and not used/connected, only 2 heating pipes which aren't too big a job to move)
2. Take out the floor
3. Patch-up the brickwork to provide a solid surface to attach the new floor
4. Install wooden header plates onto newly patched brickwork, using resit bolts both sides of the room
5. Hang new joists off header plates with joist hangers
6. Install noggins into the new joists
7. Use a router to cut out channels for pipework
8. Re install old and add any new pipework needed

Does that seem like a sensible plan? Is there anything blindingly obvious I need to include!?

I also have some questions generally about the best way to approach things:

1. The joists on the exterior wall side of the room are set into the brickwork as per the pics below. I've seen different schools of thought on whether it's best to reuse this approach when renovating. Does anyone have any recommendations as to whether it'd be best to reuse the current "joists set into brick" method (while covering the wood ends and insulating so prevent damp issues)? Or should I fill in the voids where the joists used to sit and use a wooden plate secured onto the wall with resin bolts?
www.matt-k.com/downloads/house/bathroom/floor/joists_into_dodgy_brickwork_2.jpg
www.matt-k.com/downloads/house/bathroom/floor/joists_into_dodgy_brickwork.jpg

2. Generally is it better to use joist hangers set into brick, like this:
www.matt-k.com/downloads/house/bathroom/floor/joists_hanger_into_brick.jpg

.... or a wooden header plate which is secured into the wall using resit bolts then joist hangers hung, like this:
www.matt-k.com/downloads/house/bathroom/floor/header_plate.jpg
I'm wondering whether the hangers into brick might be better for blockwork walls rather than for old buildings, of brick construction?

I know it's a long question so cheers if you read everything and got to the bottom! Any advice would be really appreciated!

Thanks, Matt

 

[Mr Chibs]

Lots of info

How many joists are sat on what you are calling the 'dodgy header'... its not the whole floor is it?
How big is the floor that's bouncy?

 

[Matt K]

Yes I thought the more info the better!

It's is the whole floor sitting on the dodgy header yes, 10 joists in total.

The room is 3.7m x 2.4m, so not huge but should make a decent size bathroom once done.

Cheers, Matt

 

[tomfe]

Sounds alright. Though sounds a bit Ott.
As you've said your wall plate has started to come away but it's just the size of your joists which is causing the bounce. Removing the ceiling will also have added to the bounce.
Timber floors do bounce though.
You could double up some of the original joists especially around the bath and add a new wall plate.

 

[John D v2.0]

While your ceiling is down consider glue and screw plywood to the bottom. The bottom and top edge is the most critical for bounce hence why I beams exist. Then do the same on top without the glue.
In my case I also glued long strips to the sides of the joists nearly as high as the joists.
It wasn't cheap though in materials or time.
I'm not sure how much of it is placebo effect but the difference seems immense.
Of course I didn't want to replace the joists so that was the best I could do with the existing over notched joists.

 

[JohnD]

herringbone strutting stiffens a floor. Noggins are just for supporting cut floorboards.

Herringbones push against the adjacent joist, if one joist tries to bend, as they are diagonal. They have to be quite tight.

You mention taking the floor up. If you lay the largest sheets of 18mm WBP ply that you can carry, and screw them down tightly, they will form a deck with the joists and again, make it more rigid. Have the biggest pieces in the middle, and do your cutting and trimming to fit the edges. Do all your wiring and plumbing first. IMO it is better to use square-edge as it can be lifted easier in case of need, without having to saw through tongues or cut traps. opinion may differ on this.

I have not tried a lower deck on the underside of the joists but it sounds plausible. You can add dense mineral wool batts while you are about it, between the joists, to help muffle noise.

Verify that all the joist ends are firm in the wall. You can foam into small gaps to stop draughts.

You can use timber preservative against rot and worm, especially in the bathroom and kitchen which may have overflows.

If you have bad notching of the joists, post photos on here.

 

[Mr Chibs]

If the other ends of the joists are embedded in the wall, you might not have enough wiggle room at the 'header' end to use joist hangers (and get them level), so you may just have to renew the header plate, are you able to pass a bolt through the wall, if not perhaps you could resin and threaded bar to secure it to the wall.

 

[John D v2.0]

Oh yes JohnD has a good point about struts, the reason I started adding plywood to the sides was to add strutting without disturbing the ceiling. However measuring it all out was a massive pain so I'm not sure I'd recommend my way.
Let me find a photo of my efforts

 

[Matt K]

Hi all,

Thanks for the advice so far, I've managed to strip out the floor and reroute the pipework. I'm now ready to install the new floor.

Bit of context, as you can see from some of the pics, the brickwork is not in great shape:
www.matt-k.com/downloads/house/bathroom/floor/joists_into_dodgy_brickwork_2.jpg
www.matt-k.com/downloads/house/bathroom/floor/joists_into_dodgy_brickwork.jpg

Although I'm going to repoint all of the internal wall/leaf, I'm still not sure which joist hangers I should use because of the points below. I'd really appreciate some advice please!

I'm almost certain I don't have a level mortar line around the room, so don't think I can use the SAE joist hangers such as these, without cutting out a lot of brick for parts of the brick which have settled out of line over the years:
https://www.metrofixings.co.uk/main...n Strong Tie Masonry Joist Hangers/1627/0/0/1

Apparently using the "header-plate on resin bolts method", means that there are fewer anchor points between the joists and wall, as a result that might not be the best approach. I'm told that I should use an SAE Hanger, such as the ones below from Simpson, my concern is that means I only have 1-2 bricks to anchor to for each joist, due to the height of the hanger. Considering the quality of the brickwork that seems risky again. Is there a Jiffy type hanger such as the Simpson JHA that "goes up the wall" further allowing me to attach each hanger to 4-5 bricks rather than 1-2??

I guess my question is, can I get a timber to masonry joist hanger, that enables me to connect the joist to say, 3-4 bricks up the wall, that would looks like this, but is good for masonry rather than timber?
https://www.travisperkins.co.uk/Simpson-JHA450-100-Timber-to-Timber-Joist-Hanger/p/529819

.... Rather than this (doesn't seem to go high enough to allow me to attach to several bricks rather than 1-2):
https://www.metrofixings.co.uk/main...impson Strong-Tie SAE380/38/2/25 38mm Width/1

If not, is it really OK to attach the joist hanger to 1-2 bricks using the SAE hanger, and expect that the floor stays on the wall while supporting a bathroom!?

Cheers again, really appreciate the help/advice on this forum!!

Matt

 

[Mr Chibs]

On your previous images, the one where you are pointing to the 'header'... is this a solid single skin masonry wall?

If yes, then I think I'd sort the brickwork out, you could then use standard timber to masonry hanger, if this can't be attached in the mortar line i.e it's not level, then you can grind/drill a slot into the brick(s) and mortar-in said hanger.

If this 'wall' is a stud wall, then perhaps a different method is needed.

 

[Matt K]

Hi Mr Chibs,

Yes you're right, in that picture is the solid single skin masonry wall I'm attaching the hangers to. There is an external wall on the one side of the room and a dividing with neighbours on the other. So there are effectively two cavity walls either side of the room, the internal leafs of which I'll be repointing.

Quick question on the masonry hangers, if I were to grind/drill into the one of the type of hangers with an "L" at the top (like the ones at link below), would I be relying on only the mortar holding it into the wall? as I cannot get access to the top of the brick to anchor through the holes on the top of the "L" on the hanger.
https://www.metrofixings.co.uk/main...n Strong Tie Masonry Joist Hangers/1627/0/0/1

Would I be better to use a resin bolt hanger like the one on the link below, on the face of the repointed brick maybe?
https://www.metrofixings.co.uk/main...vy U Face Fix Joist Hangers SAE/1940/0/0/1/12

Thanks for any help, sorry about all the questions, just want to try to get it right!

Matt

 

[Mr Chibs]

I'd would use the masonry to timber. These are embedded in the wall and when you mortar them in, you are spreading the weight to the whole wall.
I would not use any additional fixings through the top of these. When the joist in inserted, they cannot fall out.

Your resin bolt idea is also good, but your wall is not (looking at your images). Either method will do the job.

If you wanted to go the whole-hog, you could refit the wooden support (header) under all the re-fitted joists, and resin into the wall.