Breezeblock wall built off floorboards supported by rotten joist

[nebjamin]

Hi All

In the process of renovating the WC. Have pulled everything up to find that one of the joists has been hacked in the past and is pretty much rotten through (presumably due to leakage from around the drain).

To make things more difficult, the wall in the pic is built off the floorboards which in turn are supported by this joist and one on the other side of the wall (which is sound).

I guess it must've been like this for some years, and there's no sign of that wall moving (but the joist can be moved by just pressing it).

The joist seems pretty solid about 20-30cm either side of the rotten hacked bit.

How to proceed here? Sistering with another joist will be tricky due to the concrete holding the drain in place (presumably why they hacked it up in the first place).

Would something like a steel plate fixed either side of the rotten bit work?

Thanks
Ben

 

[vinn]

OP,
Before you do anything else I would suggest that you clear out and sweep up all debris etc.
Then remove the cistern and basin after isolating the supplies.
Also release & remove all skirtings.
Next you want to lift all floor boards that will lift without cutting.

The joist in the pic is totally shot & must be replaced - its probable that all the joists and some of the boards are also decaying due to proximity to the oversite soil and lack of ventilation - where's the nearest outside wall?
Some of the boards have been cut & are landing on fresh air.

What is on the other side of the wall (its probably a stud frame partition - can you post a pic of the floorboards on the other side?
Can you also post a pic, showing all the bathroom floor with all possible boards lifted - from the entrance doorway?

Why have you smashed the upstand to the soil pipe hub? If necessary, it should be cut with an angle grinder.
Presumably, you have another WC?
Is that soil bend half full of water?

What do you intend for the WC compartment - for the left and right walls?

 

[nebjamin]

@vinn Thanks for the response. I'm reasonably competent and have verified that none of the other surrounding joists are rotten, it's just this one.

So, appreciate the help but let's not worry about all the other stuff just yet - the question I posted is what to do about this specific joist. I imagine complete replacement will be very difficult due to the wall which is built off the floorboards. Even though the joist is rotten in the middle, since the joist is quite long (and hence cantilevered to a degree by the weight of the adjoining room), I believe it is still supporting that wall. Taking it out completely will likely result in that wall dropping.

 

[vinn]

I understand thoroughly how the joist is situated, and most of the info I was asking for is, believe it or not, to enable you to do a quick, correct and lasting job of work.

I notice that you have posted more informative pics in the plumbing forum - there are some good tradespeople in there, I hope that they can help you.

 

[^woody^]

Treat the rot.

Bolt a new joist section that is a bit wider than the toilet width to the rear side of it, and support off a hanger in the wall.

Bolt it with two m10 bolts with square washers on the ends and a timber connector 'spur' washer between. 300mm apart and 100mm past any soft timber.

Don't worry about the wall as the load is spread along the other hosts and it's wedged against that other wall, and likely tied to it too.

 

[vinn]

"Treat the rot" - how?
The joist is beginning to form cuboidal cracking across the section: the only method of treating such a decayed joist is to remove it well past any signs of decay. Chemicals alone wont work.
In other words, given the narrow span, remove the joist from wall to wall at least.

Bolting-on to a joist in that condition is to add good to bad - fungal decay will affect the sistered joist.
It will also continue to infect the undersides of the floorboards.

How a joist hanger is to be used I dont understand but by the time taken up by bolting-on, and "supporting off a hanger in the wall" it seems quicker and simpler to replace the joist as I mentioned above?

 

[^woody^]

Once the source of wet rot is removed, the rot stops.

How taking up the floor to needlessly replace a whole joist (if it can even be slotted in under that wall) is quicker than replacing part of it by widening an existing hole in the floor i don't understand.

 

[nebjamin]

@^woody^ Thanks - I was thinking something along those lines. Thanks for the detail. The joist seems sound where it's supported in the wall and getting a hanger in there (under the breezeblock) would be difficult. So, bolting a new bit in either side as you suggested would probably do it. AAMOI the breezeblock (or clinker, whatever: it's not lightweight) is not tied in... it's just sitting on the floorboards! This toilet and wall is not original. No sign of movement though, and the joist is very dry, so I think it's been like this for some time.

@vinn did your alias used to be ree?

 

[^woody^]

@vinn did your alias used to be ree?

You know, that is what I have suspected for a long time. "Ree" was not as grumpy, but he loved the questions and pictures just the same.

 

[^woody^]

the breezeblock (or clinker, whatever: it's not lightweight) is not tied in... it's just sitting on the floorboards

It's still wedged in and the rest of the floor is load-sharing, so a single joist does not make much difference in the short term.

 

[vinn]

Your proposal to merely "treat" a joist that has failed with severe fungal damage goes against all good remedial practice. No Remedial advice, that I'm aware of, would allow it.

From the pic - the whole visible section of the joist will have to be cut out leaving a LH stub & a RH stub but my experience tells me that, actually, most of the joist will be at risk.

The rot will not stop, the fungal infection will continue to be fed moisture by ground conditions (bare soil) and ambient humidity in that unventilated space.

There is nothing "needless" about doing a job properly - from what I can make out of your method, almost as much floor will have to be lifted as doing it my way.

"slotted in under that wall" - what wall? Which wall are you referring to?

"widening an existing hole" means taking up enough of the floor for you to bolt-on, and somehow use the "hanger" you mention.
FWIW: Why use a hanger with a short piece of bolt-on material?
By the time you've "widened the hole" you will have enough space to replace the joist with guaranteed sound material.

Anyway, your convoluted method would be difficult enough for an experienced person but will be well difficult for a DIY'er.

 

[^woody^]

No Remedial advice, that I'm aware of, would allow it.

Well, now you are aware of it.

"Would" "you" "like" "me" "to" "upload" "some" "photos" "to" "help" "you" "?"

 

[^woody^]

Read this quick before the mods delete it

And just what are you infering? LOL

 

[nebjamin]

@vinn You are making assumptions, many of which are not valid. The rot in that joist is not from being in contact with the soil. That is not soil. It's concrete that holds the clay waste pipe in place. It's not in contact and it's bone dry. And it's not unventilated down there. It's very well ventilated. So I believe that rot to be historical wet rot.

I've used these forums for at least 10 years and I see your posts all the time - you may not intend it but your posts come across as quite patronising. That you asked me why I smashed up the clay drain collar tells me immediately that you think I'm incompetent. It didn't occur to you that this is what I found after removing the floorboards.

The responses which I find most useful are those which give direct, focused advice about the specific question asked by the OP.

 

[vinn]

^woody^

Why do you feel so threatened whenever you are challenged?
You lost the argument the moment you ducked answering my questions. The moment you ran away.
You are not a Remedial expert or an authority on Remedial work as your suggestions prove.

I'm sorry that you are unfamiliar with quotation marks, perhaps you should brush up on remedial English - & Remedial building practices?