Soggy piece of wood holding up floor joists

[Londonterrace]

Hi all,

Another request for advice. Apologies for another damp question…I know you get an abundance.

My house is a Victorian terrace. A few days ago we noticed the downstairs floor was ominously springy and lifted the floorboards. The springy area is in the back reception room, near to the back wall. Half of this wall has the side return on the other side and the other half has the kitchen.

About half of the joists seem to be resting on a piece of wood running perpendicular to them (so in line with the floorboards). This is turn is resting on brick piers. The piece of wood is damp to the touch and rotting. After some time with bowls under our plumber’s shocking joins, I don’t think there’s a plumbing leak. (We did find a bonus unrelated plumbing leak further down in another part of the wall though. Such fun!) The wood is wettest at the bottom and looks salty where it touches the brick piers which to me suggests it is soaking water up through the piers?

I don’t think the ground level is too high (certainly not touching the wood) and I can see through the two air bricks in the part of the wall that communicates with the outside.

What’s this piece of wood called and can I stop it drawing water in through the brick pillars (if that is indeed what is happening)? Does it need to be replaced with metal?

Why has this just started happening? I don’t think the floor was springy a year ago.

Thanks for any help!

Photos going from left to right along the wall:

Now we reach the bit that was spring and where the beam looks most in trouble. Despite the suspicious proximity of the plumbing, nothing coming from the pipes:

It ends and the remainder of the joists touch the pillars directly, or at least hang on scraps of wood on the pillars:

Then this second joint is leaking (very slowly), but hasn't made the joist above it or the ground wet, just the pillar it is above. So I think an unrelated problem:

 

[MatthewC]

Hi there

What a lovely set of pictures! I know the piece of wood you mean and I would term it a "wall plate", although on my blog I have used "sill plate" as an alternative. Strictly "wall plate" refers to the piece of wood which transfers the roof load to the top of the wall. Personally, I think it is correct here because it is transferring the load from the floor to the wall (or individual piers) below. I cannot find any definition for it, but I'm sure someone will be along with a good term (or else agree with me!).

It certainly should not be damp but frankly I am not surprised it is, as there clearly has been no decent ventilation there for a long time. Under my suspended floor the joists were supported by three wall plates on small walls (3 bricks high, IIRC), just as you describe. However, saying that the (single?) vent is unobstructed does not mean there has been good ventilation. On my floor I thought it necessary to install a floor vent on the far side of the room from the wall vent and your floor is awfully low on clearance so I am not surprised that any dampness was unable to be ventilated.

The worst bits of rot in my floor were where the boards and the end joist abutted an external wall with concrete at floor level on the other side. However, there was dampness in various places, especially where the ground level had been built up or (beside the fireplace) had been FILLED IN with rubble!

I reckon you will need to replace the rotten wood with decent wood, clear out some of the ground to improve ventilation and add a floor vent or two. Or, of course, do a limecrete floor instead!

See entries on my blog, such as http://houseintheenchantedforest.blogspot.com/2010/11/is-it-really-only-three-weeks.html and http://houseintheenchantedforest.blogspot.com/2011/03/floor-to-dance-on-and-mystery.html

 

[Londonterrace]

Thank you Matthew. I hope I don't have to make any repairs as extensive as those in your blog. I'm still vaguely hoping it might be possible to correct this without taking up the entire floor.
In terms of excavating the ground, how do you know how much is too much? I'm nervous of disturbing the brick piers +/- wall. There is a bit of debris in there but no serious rubble, and I can still clearly see the earth floor at what I presume is the original level.

 

[Flyfisher]

The description of 'dodgy plumbing' suggests that it might have been recent water leakage that has caused this problem, rather than there being a fundamental problem here, especially if the floor was not 'springy' a year ago.

I would be inclined to leave the sole plate/sill plate well alone but to add some additional support under the affected joists to remove the 'spring in the floor. I have an entire suspended floor with the joists supported on bricks and tiles sitting directly on the earth subsoil and given the good underfloor ventilation it is perfectly fine. Based on this, my approach would be to clear some space under the affected joists close to, but not touching, the sole/sill plate and place an engineering brick (or two) under each rafter to provide additional support. That should make the floor rigid again.

The trick will be to ensure the brick is 'tight' under the joist. If possible, lift the joists slightly somehow (car jack, long crowbar etc) and pack under them with some pieces of slate or similar thin but solid material so that the joists rest tightly on the new supports. If you manage to use slate then it will also act as a damp-proof course to keep the joists dry (though using engineering bricks will also help in this regard anyway). If you really wanted to be sure, then you could cut some plastic DPM to fit under the joists or between bricks.

I suppose that purists might consider this approach to be a 'bodge' compared to lifting the entire floor, removing the compromised sole/sill plate and replacing it with new oak before replacing the floor, but I'd wager a small sum that the above approach would last at least until next century and I'm not sure of the timescale definition for when a 'bodge' becomes an actual solution :wink:

In any event, I don't think there is anything to panic about and certainly nothing that would necessitate the expense, upheaval and destruction of a limecrete slab.

 

[MatthewC]

The description of 'dodgy plumbing' suggests that it might have been recent water leakage that has caused this problem, rather than there being a fundamental problem here, especially if the floor was not 'springy' a year ago.

I wondered that, but surely the sill plate would not have rotted that much in a short space of time? It sounds much more like long term dampness.

 

[Flyfisher]

I picked up on the floor becoming springy in the last year: "Why has this just started happening? I don’t think the floor was springy a year ago. "

Could it be that it was already weakened affected and leaking plumbing was the last straw? Or was the springy floor not actually noticed until recently, in which case I'd tend to agree that the sill plate might have been affected for some time by a more fundamental problem.

Either way, additional supports for the joists as I described would fix the immediate problem, though for how long could be up for debate.

I suppose the crux of the matter is what does a 'fundamental problem' mean in practical terms, ie time & cost A thatched roof is a fundamental problem as it will only last for 30-odd years without significant attention, ie a relatively short time and very expensive. My roof pantiles have a fundamental problem in that they gradually break up (I've replaced three already this year), ie a recurring problem but quite cheap to fix. My heating system has the fundamental problem that the gas boiler will probably only last 10-15 years, ie another short time though relatively cheap to replace (assuming we still have mains gas in 15 years - perhaps a big assumption!).

Thus, a spongy sill plate in a 100-200 year old house may or may not be a fundamental problem if the resulting springly floor can be relatively easily fixed with some additional support - depending on your perspective. After all, nothing lasts forever.

Or perhaps I've just become too relaxed about the shortcomings of an old house over the last 15 years or so. Certainly, as I get older such problems seem to be less worrisome.

 

[CliffordPope]

Houses have always had built-in problems - they are made that way. The generally accepted life-span of a newly built house is 60 years.

The Victorians were among the worst jerry builders of ordinary houses. Our standard Victorian terrace in London was supported on about a dozen rickety brick pillars about 2 feet high. Where they had moved over the years they just hammered in more wooden wedges. Where a support rotted they knocked up another pillar under the nearest sound portion of wood and nailed an additional support next to the rotting one.
The projecting rear of the house had started to tilt from the moment of construction. The crack was about 2" wide up in the roof, and they obviously just adjusted the building as it was built. 100 years on it had stopped widening, and become full of soot and all sorts of debris. The tilt was small but perceptible in the corridor running towards the kitchen. My wife in a wheelchair could freewheel down into the kitchen but found it harder work coming back.
35 years later the house is still standing, now worth nearly a million.

 

[Lacan07]

Its called the 'plate'. They never used to bother applying a DPC to the brick wall it rests on so this can happen from time to time, usually in the corners. Cut out the rotten section and replace with treated wood of similar spec, buy a roll of DPC and place between the wall and your newly inserted section. Job done.

 

[malcolm]

My worry there is that the wood is soaking wet in the photos. You've got 100% humidity under there. It's starting to dry where the floorboards have been removed. I like Flyfisher's ideas as a solution to the immediate structural problem, but if you cover it up again it'll need a new floor.

Wet wood will rot. You've got to keep wood dry to avoid rot. Whatever plumbing leaks you might have you don't have enough ventilation under there. Also make sure all the wood has air space between the wood and the earth.

Cross ventilation is important. If you only have air vents on one wall that's not enough. You want air wants on the opposite wall so the air can pass through and pick up moisture on the way. Has someone put a concrete path or patio on the opposite wall? Pull out a few flags and expose the airbricks.

It's well worth having a flip through the Pete Ward videos on Youtube :https://www.youtube.com/user/stibnite11/videos Lots of underfloor damp issues there and sensible ways to fix them.

 

[Londonterrace]

Thanks all for the good advice and reassurance. This has been very cheering. Flyfisher I like your solution and will probably do that +/- trying to add some plastic membrane between the brick pillars and sill plate. If it is a bodge it's a benign one compared to much of what has been done to this house.
I take the point about the ventilation/clearing out the the cavity and will try to get the other nearby floorboards up (the radiator needs to come off the wall first) and have a better look. When I put my hand on the sill plate, I can feel a slight draft, so there is air moving. But I'll check the air bricks across the ground floor and see if the others needing clearing out. They are all still above the external ground level if I remember correctly. Internally, the floor of the front bay window is a concrete slab, but I'm hopeful it's lying on joists with air flowing underneath...I'll check.
The joists and boards are all dry and all the wood is clear of the earth. The portion of the plate that was particularly rotted is further away from the air bricks (and I think next to the kitchen so no possibility of adding one) and possibly touching the wall more than the rest of it, so maybe that's why it's suffered. Hopefully it will be easier to tell once more boards are up.
Thank you!

 

[88v8]

Air bricks are vital. No airflow = eventual disaster.

I agree with inserting dpc beneath the wood.
All the brick piers/dwarf walls under the floor should have dpc in or on them.

The plumbing... plastic fantastic... what on earth is that supposed to be??
And the little lengths of pipe insulated, but not the corners.... ye gods.... this person claims to be a plumber?

Ivor

 

[CliffordPope]

The plumbing... plastic fantastic... what on earth is that supposed to be??
And the little lengths of pipe insulated, but not the corners.... ye gods.... this person claims to be a plumber?

Ivor

Good plumbers don't use corners, they make beautiful bends in copper pipe.
Corners slow down flow rates and reduce pressure - there's a set of tables somewhere for calculating the effective pressure drop per length of different diameters of pipe and the number of bends of different radii. It can all add up to quite a lot.

 

[Cubist]

The plumbing... plastic fantastic... what on earth is that supposed to be??
And the little lengths of pipe insulated, but not the corners.... ye gods.... this person claims to be a plumber?

Ivor

Good plumbers don't use corners, they make beautiful bends in copper pipe.
Corners slow down flow rates and reduce pressure - there's a set of tables somewhere for calculating the effective pressure drop per length of different diameters of pipe and the number of bends of different radii. It can all add up to quite a lot.

I must admit that I have always admired the skills of some tradesmen. Particularly those plumbers who could intuitively bend copper pipe into the sometimes arcane shapes needed to precisely navigate whatever obstructions they encountered.

Personally I have no time for those push fit plastic fittings, partly because unless they're properly prepared the likelihood of a leak is, in my opinion, much greater than with a soldered or compression metal connector.

My bias though results in large part from the time I was replacing the kitchen sink here and found that the 'plumber' - the PP website won't let me use the term that first came to mind - that installed the original sink had used plastic pipe to connect to the copper supplies and had used, get this, no fewer than EIGHT push fit elbows to connect them to the new mixer tap. All of them completely unsupported! When I uncoupled them from the tap the whole perishing lot collapsed on the floor like a pan of spaghetti and went in the bin in the same state.

 

[MatthewC]

Good plumbers don't use corners, they make beautiful bends in copper pipe.

Yes, a good plumber does do beauty. I recall the chap who did the new pressurized tank in my posh flat in London; the new one really was a work of art, with all the shiny copper pipes parallel and then bent uniformly on the cone at the top. We were south of the Thames and he usually worked only on the north; there were very few places on the south that he would deign to visit!

 

[LadyArowana]

Good plumbers don't use corners, they make beautiful bends in copper pipe.

Yes, a good plumber does do beauty.

Yes and then unwise homeowners gush about how fabulous they are and they go off to make candle holders and all manner of arty stuff and don’t want to do boring sinks and boilers any more….. https://www.notonthehighstreet.com/copperandhall/product/copper-candelabra

 

[Cubist]

Good plumbers don't use corners, they make beautiful bends in copper pipe.

Yes, a good plumber does do beauty.

Yes and then unwise homeowners gush about how fabulous they are and they go off to make candle holders and all manner of arty stuff and don’t want to do boring sinks and boilers any more….. https://www.notonthehighstreet.com/copperandhall/product/copper-candelabra

My father, call him a perfectionist or a pedant - he was an engineer who celebrated the introduction of Metric units so that he could play with Microns rather than Thous - taught me that I must always be precise when cutting copper pipe, that I must properly de-bur it and tin the ends before soldering a joint. Oh, and to clean off the flux residue after making the joint as it rapidly oxidises to produce unsightly verdigris.

But thats not my reason for replying. After finishing the modenisation of our bathroom I was left with lots of unused copper pipe and fittings that, quite simply, I did not want to carry back to the shed. Fortunately the First Lady came to my rescue with an idea to create a towel rack similar in design to the luggage racks one sometimes sees in old train carriages/coaches.

Had to remind myself though that it can sometimes be unwise to try to solder, or weld, a closed pipe. :roll:

 

[88v8]

I made this heated towel rail to fit a space in the downstairs loo of our previous house



The air vent is top left. Valves were Crane D201 and D200, bought from BSS in Clerkenwell.
It was anchored to the woodwork with iron skirting fittings.
I should have made it with all end-feed fittings for neatness, but I hadn't enough so used some Yorkshire, which for ever after niggled me.

Ivor