Giving a wooden floor the best chance against rot?

[CluelessDIYer1]

We may need to replace our wooden floor - the floorboards themselves & also the joists.

Problem is - the actual cause itself cannot be solved. There's water occurring underneath the floor naturally & this can't be stopped. So it's a case of managing it.

The house is 80years old & i dare say the floor system is original. Who knows, it may last another 50 years or so, but the ends of the joists & some of the boards themselves have gone quite mushy.

JOISTS:

I dare say these will have to be tanalised. Beyond this i'm not sure.
Would you coat them with some wet/dry rot treatment & then hardener as well as?
I've been told about Boron as a preservative. Would you slap this on as well?

If it has to be replaced i don't fancy cutting corners for such an important section, but at the same time, what would all this extra treatment on top of the fact it'll be tanalised give us? Any real extra benefits or are we talking about it may give us an extra 5 years lifespan, that's all?


FLOOR SYSTEM:

I thought floorboards but i spoke to a customer at work who said 22mm moisture resistant chipboard.

I emailed Kronospan who disagree as they don't believe MR board is likely to be suitable in this situation. They go on to say they don't really know WHAT would be suitable. Well, we need SOMETHING.

So what would you go with on this & would you give it any extra treatment like the joists?


Oh & there'll need to be some sort of hatch system to the subfloor (as is currently in place). We have a sump pump that kicks in every so many days so obviously we'll need access under there.

 

[foxhole]

Install a ground water pump to remove water. [all problems can be solved]

 

[AronSearle]

+1, solve the problem properly.


If you cant, or just need some extra protection whilst the problem is addressed.

Joists


Pressure treated, aggressivly re-treat cut ends, make sure they sit on some DPC if they go into the wall, with airspace around the end, sides and top (so lose within the brickwork). Some may say wrap the ends in DPC, my concern is that might trap moisture as much as prevent it getting in if the problem is atmospheric rather than direct moisture transference.

Floor.

Moisture resistant chipboard is still chipboard, its not THAT moisture resistant. I wouldnt bother treating, if you need treatment for floorboards, you really have far to much moisture and you need to deal with that.

You could just use quality plywood or softwood square edge boards, with the idea that you fit them in a way they can be easily replaced.

Putting a VCL under the floor will keep it dry and should prevent the floorboards decaying anyway, however if there is not sufficient ventillation to the underfloor that could trap more moisture, and if you dont insulation between the joists (under the VCL) there is some risk of condensation on the VCL.

And of course the insulation can hold lots of moisture if it gets wet.

SO yea, sort out the moisture.

 

[gregers]

as above but shouldnt worry to much about problems with wrapping joist ends,because that is all you are wrapping,condensation should evaporate from other sections of the timber.

i would defo spray a combi wood treatment all over the floor etc.this will then protect against wood boring insects and rot in general.

also as said upgrade the sub floor ventilation.

 

[pinenot]

Every reply so far is spot on, trying to defeat rather than cure dampness is useless, dry and well ventilated is the only recipe for success.
The cause of your "water occurring naturally" is anything but natural, if that were so the house would not have lasted 8 years, never mind 80. So first off establish if the water table has risen since the house was built, somewhere away from the house (preferably downhill) dig a hole two or so feet deep, if this fills with water then you have found the water level, if not the water under the house is not natural, most likely a leak of some sort. By try to establish one thing at a time...dig the hole and come back to us in one day after with the results...pinenot

 

[CluelessDIYer1]

Install a ground water pump to remove water. [all problems can be solved]

We've already got a sump pump. It removes the water but it returns. We thought things would change come the summer time but nope - returns as it always did.

+1, solve the problem properly.

In an ideal world, we would.

We simply don't have endless amounts of money to throw at this though. The void is 1mtr deep & the living room is 7mtr-x-3.5mtr, the hall is approx. 1.5mtr-x-2mtr/3mtr. I was in touch with the local council who said they had someone out 30 years ago to that area & put me in touch with him. He said it's best to manage the water, not try & cure it/stop it. It has to go somewhere.

Pressure treated, aggressivly re-treat cut ends,

What do you mean by this? I assume by pressure treated you mean tannalised, but aggresively re-treat?

Some may say wrap the ends in DPC, my concern is that might trap moisture as much as prevent it getting in

EVERYONE i've spoken to says wrap the ends, but my concern is the same as yours. Partly because i'm doom-&-gloom & think everything is going to go wrong.

Moisture resistant chipboard is still chipboard, its not THAT moisture resistant. I wouldnt bother treating, if you need treatment for floorboards, you really have far to much moisture and you need to deal with that.

Thinking about it tonight, it's only where the ends of the floorboards touch the wall. The rest of it is fine. So replacing with floorboards while more expensive should be fine.

Putting a VCL under the floor will keep it dry and should prevent the floorboards decaying anyway, however if there is not sufficient ventillation to the underfloor that could trap more moisture, and if you dont insulation between the joists (under the VCL) there is some risk of condensation on the VCL.

What's VCL? I know what DPM & DPC are but VCL?

 

[CluelessDIYer1]

as above but shouldnt worry to much about problems with wrapping joist ends,because that is all you are wrapping,condensation should evaporate from other sections of the timber.

i would defo spray a combi wood treatment all over the floor etc.this will then protect against wood boring insects and rot in general.

also as said upgrade the sub floor ventilation.

Yeah the joists that are in place right now - the ends are mushy & this spans down the length a bit, but the centre parts are good for the most part.

Under there right now are 2 air bricks to the rear, but the vent is not a full air brick size as it's a 2" (guessing) by 2" square pipe that leads through the dining room solid floor out the back.
There are 2 air bricks to the front of the living room, 1 to the front of the hall & 1 to the side of the hall.

There would be room to install a further 2, perhaps 3 at the front but no more at the rear with it being solid floored.

I still (in my infinite wisdom/experience) highly doubt that this would solve the problem. I'd love to be wrong.

I guess it wont harm anything by installing more, but i just don't think it'll work as that's a huge space with just a small extra brick.

Every reply so far is spot on, trying to defeat rather than cure dampness is useless, dry and well ventilated is the only recipe for success.

Unfortunately as i've said, the only thing here is to manage it.

We're not alone. There's a few of us in the dip of the cul-de-sac who are affected by it. In different ways too. The house at the rear has a really wet garden & he had to raise it. Their house is ok for the most part. Our immediate neighbour is worse than ours. One of the houses across the street - the chap went through his living room floor.

The cause of your "water occurring naturally" is anything but natural, if that were so the house would not have lasted 8 years, never mind 80.

Like i said, i know nothing about this stuff. I was in touch with the council who put me in touch with a guy who worked on our area 30 years ago. They tried to solve it back then & couldn't. His advice was also to manage it.

So first off establish if the water table has risen since the house was built, somewhere away from the house (preferably downhill) dig a hole two or so feet deep, if this fills with water then you have found the water level, if not the water under the house is not natural, most likely a leak of some sort.

Well the void under the living room is 1 metre deep if that helps? And the sump for the pump is perhaps another foot deep.


Like i say though, these kind of things are all budget depending & we simply do not have the money to spend going down a cure route to see whether it'll work or not. I've already been & had quotes to solid floor it & when i told them how deep we're talking they almost choked & told me to sit down. We're talking many many thousands which i don't have, not with all the other things that need looking at & where we're at in life & want to be. We are going down the manage it route (i think) - new floor, new sump pump (so that we know it's new instead of the current one which may be 12 months, 12 years, who knows) & then something with the walls.

 

[freddiemercurystwin]

Your sump pump set-up should be designed so that it kicks in whenever there is any water in the sump, not every few days on a timer. The ground should be to a fall down to a hole within which the pump sits.

Do not underestimate the importance of good ventilation, add as many air bricks as is practical.

Soak the ends of the joists in preservative, even though they are treated already.

There is nothing wrong with wrapping the ends of the joists in dpm as they sit in the wall, in fact this is very common nowadays.

As mentioned MR chipboard really isn't that moisture resistant and should be avoided if at all possible especially if you want to tile anywhere as chipboard is wholly unsuitable.

A VCL is a Vapour Control Layer, more commonly known as a VB or Vapour Barrier, effectively it is a thin dpm! Or you could just use dpm if you wanted to.

About the only 'cure' if its is just a high water table is fill the void up with hardcore and then stick a dpm down with a slab on top, above the maximum height of the water table level.

 

[gregers]

if the joist ends are already weak then i would say they need cutting back,but this may require a new sleeper wall built to take them.

 

[CluelessDIYer1]

Your sump pump set-up should be designed so that it kicks in whenever there is any water in the sump, not every few days on a timer. The ground should be to a fall down to a hole within which the pump sits.

Yeah from the googling i've done on sump pumps & correct installation, this has been a DIY job.

There's the sump (let's say 1ft deep at a very rough guess) then there's the floor. The water level can get to 4.5"-5.0" I think it kicks in when the level gets a little over 5" as that's when the float is over 90degrees (it's floated, not on a timer).

If it was sorted so that it kicked in whenever the sump filled with water then the pump would literally ALWAYS be on. I timed it one time & within a timeframe of 7hrs, it has gotten back to a level of 4.0"-4.5" high from the floor.

One thing we've been warned about is it taking "the fines" out of the floor & then subsidence.
Another we're weary of is if it is kicking in every 2 seconds, then the floor drying out & cracking, although i guess MAYBE this wouldn't happen since the water flows from the back to the front, but then the sides near the wall may dry out & crack. Who knows (not me!).

It just concerns me about it always being on. I could be pumping all next doors water as well as.

Do not underestimate the importance of good ventilation, add as many air bricks as is practical.

I understand the logic behind it, i just don't think it will work. With that said, just because i don't think it'll work doesn't mean i'm poo-pooing the idea. Like i say, it can't harm things, surely, so i probably will get a few more bricks put in place.

Soak the ends of the joists in preservative, even though they are treated already.

What sort of preservative are we talking here?
The damp report we were given mentioned boron. This?

As mentioned MR chipboard really isn't that moisture resistant and should be avoided if at all possible especially if you want to tile anywhere as chipboard is wholly unsuitable.

Thanks. We're going to drop the idea of chipboard altogether.
Though i'm interested - who tiles their living room?

About the only 'cure' if its is just a high water table is fill the void up with hardcore and then stick a dpm down with a slab on top, above the maximum height of the water table level.

This was one suggestion but again is costly. Plus i'd hate to barrow & shovel 40ton+ of hardcore It was the initial suggestion by the damp surveyor but after he inspected the 'tide marks' on the walls below from the photos i provided, he suggested this would not actually work & the best course would be to manage it (sump pump) instead.

With the tide marks - while the water level now gets to approx 5.0", the sleeper wall is approx 9 course brick high. The black tide mark which i assume is from before a sump pump was installed, is 5 course brick high. This only leaves 4 course between where the water probably used to get & the joists themselves.

if the joist ends are already weak then i would say they need cutting back,but this may require a new sleeper wall built to take them.

Going to show my lack of knowledge here - why would a new sleeper wall be required?

I don't know how these things usually go, but the current joists are resting ON the sleeper wall, not into it or anything like they do at the other ends of the joists.

 

[AronSearle]

I understand the logic behind it, i just don't think it will work. With that said, just because i don't think it'll work doesn't mean i'm poo-pooing the idea. Like i say, it can't harm things, surely, so i probably will get a few more bricks put in place.

Timber floors suspended over rivers will not decay if there is sufficient ventillation, most houses are limited in the amount of ventillation, especially good cross ventillation, that you can provide unless they are built on stilts, still, MORE VENTILLATION! will help.

If you provide enough ventillation so that the airspace under the floor maintaines the same humidity as the outside air, the timber will. not. decay.

You will also need to think about airtightness to the property if you massivly increase ventillation, you don't want lots of cold draughts coming up through the floor, you may as well take the opertunity to insulation and install a VCL (plastic sheet) under the floorboards.

What I mean by aggressivly re-treat cut ends = Timber treatment penetrates much less on the cross section than into end grain, cut ends will have much less treatment in them, aggressivly re-treat means go nuts, slather it, dip it, there is no such thing as to much.

 

[freddiemercurystwin]

Well reading the OP's replies in this thread it seems to me that you can lead a horse to water ......


So to speak!

 

[CluelessDIYer1]

I'm on my mobile at work right now so will respond better łater. That last comment there is what's making me reply now:

I'd like to know what the problem is with asking more questions & trying to learn more???? I've already said I don't know about this stuff, hence i'd like to understand & learn it better. Can't do that without asking questions. Questions don't mean I'm saying you're wrong, they mean I'm wanting to learn.

So again, what's the problem?

 

[CluelessDIYer1]

Again i would like to know what the problem is with asking questions? I know you never said you had a problem with me asking, but i'm assuming that's what your comment was getting at? If not then let's not be cryptic.

You gave help, i am greatful & took it on board. From help like that we've decided not to go for chipboard flooring for example.
Anyway...

Timber floors suspended over rivers will not decay if there is sufficient ventillation, most houses are limited in the amount of ventillation, especially good cross ventillation, that you can provide unless they are built on stilts, still, MORE VENTILLATION! will help.

You need to listen to the masses & the masses say get more ventilation.

As such, it'll be something we'll very likely be getting done. Had a look tonight & we can get another 2 at the front of the living room, 1 at the side & then 1 at the side of the hall.
Not sure if that'd cause a noticeable draught, but it'll be the maximum number of air bricks we could possibly fit in & should at the very least help with keeping the moisture levels down on the timber (hopefully).

Shame we can't add any to the rear due to the solid floor.

One thing i thought about (wondered) is why the solid floor for the diner & kitchen. I know none of you can answer that, it's just something i was wondering. The diner floor area was the old outside so i can see why that is solid, but the kitchen area is still the original floorspace, but it's solid. I would assume (rightly/wrongly) it would've originally been timber to match the hall & living room.

But ATEOTD all that is is 1) guesswork & 2) pointless, as it doesn't help me any.

You will also need to think about airtightness to the property if you massivly increase ventillation, you don't want lots of cold draughts coming up through the floor, you may as well take the opertunity to insulation and install a VCL (plastic sheet) under the floorboards.

My wife & I have differing pictures in our head on the back of what you said.

She thinks that you mean a plastic sheet on top of the joists but under the floorboards.
I for some reason thought you meant under the joists to protect the joists also. One of us has to be wrong.

Whichever the location, sweating is something that bothers me. Causing sweating by trying to solve a problem. Perhaps i'm being paranoid. Either way, the hatch to the sub floor would obviously have to be free to gain access.


Thinking about it though, the independent damp surveyor said against suffocating flooring. He referred to laminate flooring, saying it wont work & went on to talk about breathing (we're going back 7 months now & my memory is poor). Would plastic sheeting as you mention cause the problems he spoke about?

What I mean by aggressivly re-treat cut ends = Timber treatment penetrates much less on the cross section than into end grain, cut ends will have much less treatment in them, aggressivly re-treat means go nuts, slather it, dip it, there is no such thing as to much.

Thanks. I was actually meaning what sort of treatment (what solution) rather than the method of application. Sorry for not explaining myself.

Right now we have i think it's Ronseal wet rot/dry rot treatment solution in. The damp report mentioned treating with boron. I guess there's other treatments too.

 

[gregers]

gregers wrote:
if the joist ends are already weak then i would say they need cutting back,but this may require a new sleeper wall built to take them.
Going to show my lack of knowledge here - why would a new sleeper wall be required?

I don't know how these things usually go, but the current joists are resting ON the sleeper wall, not into it or anything like they do at the other ends of the joists.


at the moment your joists are sitting on a wall plate that is either set within the wall or sitting on a sleeper wall,if the ends are shot and you cut back past any support you will need a sleeper wall to carry them or the floor will be hanging in mid air or invest in sky hooks.
look on the web or even here for info on floor construction.