Clunkclick

A few days ago I noticed that a small patch of the bathroom floor, 6" x 9" ,next to the bath was beginning to move up and down a little. This progressively got worse, until this evening, when it was nearly 1/2 inch down on the surrounding surface.

After cutting a flap in the glued-down carpeting, pulled it back to reveal a series of cracks clean through the chipoard, radiating in a star pattern from one point. Very odd, it looks like impact damage. The board is dry and does not appear to be suffering from dry rot.

I'm at a loss to think what caused it ? Any ideas ?


As to repair/replacement I dont want to have to remove the board as it runs parallel to and under the bath and into the next room, which at the very least will mean removing the bath.

Any ideas for quick/proprietry fixes ?


Nick

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BlackFR

I have over boarded with 12mm ply before which makes things stronger and a suitable substrate to tile on. Chipboard does seem to turn to soggy weatabix when it gets moist so its not ideal for the bathroom but its seems to be that way in most houses. Not sure if that will be any good for you, can you get your carpet off to overboard?

Or you could cut out to the nearest joists then add some extra timbers to the joists for the new board to sit on and cut a new piece of board to fit the hole.

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Bigw2069

Fill with epoxy, araldite mix smoothed over like a plaster.

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cheezemonkhai

Are you saying you have chipboard floorboards in the bathroom?

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Clunkclick

Yeah. They appear to be uncoated/untreated.

One of them (Not the one that has failed), which runs under the bath, got really soggy due to a leaking bath surround and although the leak has been temporarily fixed and the board dried out, its now got no structural strength - you can stick a knife through it no problem.

I wonder if, there is a proper way of "Tanking" a fitted bath installation to capture leaks round the bath edge, e.g a polypropalene membrane or bitumen ?


Nick

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Kandy

Sounds like someone got out the bath a bit too heavily?
Chipboard can be quite fragile (but water resistant, usually green, is fine for a bathroom). It is made from resin & ground up rubbish and can have weak unbonded areas. The groove joint is often a weak point - they are supposed to be fully glued on installation but many people don't bother.
If the background is very uneven, fixings too far apart, the joists too far apart, or the joins running parallel to the joists instead of across, then it'll be prone to movement/flexing and hence break out.

If you don't want to replace or board over as suggested, the only solution is to cut the damage out and replace (make a template to get a good fit or use a holesaw if area is small enough) and screw battens/boards underneath and across the damaged area/to side of joists as required, screw the 'patch' down to these. Sink all screws slightly, glue and fill edges/heads as required.

Pipes/wires - drills/saws etc.!

Kandy

Having just read your later post about the leak - I suggest you take the floor up and replace anyway - you can check the joists aren't quietly rotting away at the same time!

It could well be the joists/adjacent boards warping have caused the damage.

Clunkclick

Definitely an action to be undertaken during my next leave period - I don't want to be without the bath for too long !

The floor as originally laid had a "hump" at the location of the break and, I think, subsequent building settlement emphasised the raised portion. It just so happens that the break sits on this raised portion as well as being the prime landing point for feet coming out of the bath -double whammy !

Nick.

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pittVRS

Replace with Marine Ply or even hardwood flooring if you can afford it. Hardwood bamboo is incredibly resistant to water ingress.

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cheezemonkhai

So they don't use real floor boards in houses these days when building them?

What a heap of .....

I'd have it cut and as above have it replaced with either marine ply or real floorboards with a vinyl or similar layer over it if you don't mind vinyl.

It's shocking how much they save money these days. Cheap and short term

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Interphase

What we used to do for delaminated skateboards was to mix sawdust of different density (depending on the severity of the damage) with PVA glue and then spread that into the gaps before clamping them shut. The stuff sets rock hard when it's cured.

flinty

Most modern houses have tounge and groove chipboard flooring throughout. If the damage is bad enough to need to replace flooring the best way is to cut it along the middle of a joist with a circular saw set to a depth equal to the floor thickness. Replace the damaged section then screw at staggered intervals along the join. Smaller areas can be cut out and fixed by bridging the join with battens screwed underneath.

The most important thing is to find and stop the leak. Tanking is no good. It will just channel the water to somewhere else. Usually the area under a bath or shower stays dry so this is not a problem. Check the silicone around the edge of the bath. Gaps in tile grouting can cause water to run down the back of the tiles. A badly fitted shower screen or careless use of a curtain can cause water to run down the front of the bath panel.

Check the bath is secure, if it moves the seal around it will fail. Check the feet are all adjusted to take the weight of the bath. Some plastic baths need battens fixed to the wall anong the back to stop movement.
If you need to re silicone, make a thourough job of cleaning off the old stuff and make sure it is dry before re siliconing and fill the bath with water to nake it settle before running a bead of silicone around the edge between the tile and the bath. Smooth it in using a round edged tool regularly dipped in soapy water. (I use my thumb but some sealants are poisonous so take care!). Allow to cure fully before using the bath, I allow 24 hours to be sure then hose down the area with the shower to check for leaks.
Water is a pain, if there is a gap it will usually find it. A small leak ofer time will damage most kinds of wooden flooring, and will often not show itself until damage is done.

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flinty

Just re read the post and realised the leak isn't under the bath!
Carpet in a bathroom is always a bad idea, Laminate flooring even worse. If you want to keep these then a thick bath mat will help catch drips and stop them soaking through to the flooring. If the floor was 'proper' floorboards the water would probably have rotted them or tracked through and damaged the ceiling below.
I think the only suitable flooring in a bathroom or toilet is tiles or good quality lino. I once had to tell a customer, 'your toilet isn't leaking, could you ask your husband to either stand closer or sit down!'
Not nice

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heresmo

If I may, and not necessarily in sequence, and please bear in mind that I know nothing.

If the board has factured, it might be that there has been a leak at some point before so warping the joists slightly (which might explain why you had a bump where you stand out as water will expand wood. Joists are rarely seasoned as they used to be in the good old days. Chipboard isn't flexible (unless it's wet, lol).

For repair, I always reckon that a bad bit should be cut out from joist to joist and possibly with an extra baton for support screwed to the side of each joist as modern joists are very narrow, widthwise. Put another way, cutting out a bit of chipboard and screwing a batton to the underside of a big piece remaining would not be my choice as the integrity of the whole board would be compromised just from cutting a bit out. (In other words, the flexing absorption distance of stress being broken - me not an engineer, but I know what I mean).

Re sealant and black mould on top and the tons of cleaners marketed to remove it - in my experience, it's caused by damp coming up from under, not lack of surface cleaning skills re the sealant. More likely that the sealant isn't sealing any more. If the sealant is removed, thus leaving a gap, stuff some tissue/toilet paper in for a while and see if it comes out wet.

They used to put chipboard throughout and marine ply (as pittVRS says) in the bathroom. These days, it can be all chipboard.

As another said (I think), it's better to lay loose lino and pref not carpet on a fibreboard bathroom floor Take it up periodically, take off the side panel of the bath, get a torch and see what's going on (hopefully nothing). A paint-on waterproof sealant might help if it's properly dry and only bog standard chipboard, incidentally, though it does mean, as said, that water will just go somewhere else Tsk!

Needless to say, baths are rarely set on lino, it starting at the panel usually, so water will happily find its way down the panel of the bath

Going back to the fracture lines, I'd think it must be dry to cause those (and a fair weight to boot), If the chipboard is reasonably OK (not breaking up, just cracks) and you can get at it, could you use a spirit level and pack one of the joists as necessary and paint lots of rubber PVA into the cracks?

Mo in overdrive

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Clunkclick

With the Saturday shopping out of the way, I've had the opportunity to pull back the carpet and had a closer look at what's happened.

First of all, the degradation has only affected a 12" square section, at exactly the point where one's foot alights when getting out of the bath - feet away from the taps and waste outlets and on the open (as opposed to enclosed) side of the bath

Second the chipboard has parted company in itself, delaminating, if it can do such a thing, along its horizontal plane. When I removed what I thought to be the broken section in its entirety, I found to my horror a separate piece corresponding to the bottom surface had already parted company with the bit bearing the top surface (Carpet side) and had obviously been laying on the top of the plasterboard ceiling below, together with wood shavings debris.

So I'd been treading on half-thickness board for some time.

Joists look A OK !

I can't understand this, as 99 % of the time I use a rubber backed bath mat over this position, so I am doubtful that damp in the carpet has caused this problem.

So what I think has happened is that the boards were originally fitted with insufficient clearance between them, which together with slight building settlement has caused them to be in continual compression width ways - presumably causing "Bowing" . Add the flex caused by me demounting from the bath and hey presto, you got the recipe for a long-term delamination fatigue crack - either that or I've got a heavyweight poltergeist !

Obviously, this is something that might not have happened if sufficient expansion gap had been left or if floor boards were fitted as these would have a greater range of flex before failure !

I've been down to Wickes, they have a couple of ranges of tongued and groved floor boards (£17 for 4), which if coated with a few coats of marine varnish, will probably do the job. If I'm lucky, I will be able to leave the bath in situ, lever out the old chipboard and slip the replacement boards into place - I don't think I would be able to get away with that using replacement chipboards as they are too wide. Only thing is that that the floorboards are centre tongued whereas the chipboard is tongued on the lower edge - Oh err missus ! So a bit of cutting will be required on the chipboard.


Nick

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Clunkclick

Forgot to say, joists centres are 14" apart. Is that too wide for 18mm chipboard.


Nick

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trundlenut

Just for good measure you could put a couple of braces across between the joist for the new boards to lie on. In my old house one of the boards in the bathroom disintergrated along the tongue and groove, I discovered the board went through into the bedroom so I bought a steel sheet from B&Q and screwed through it into the floorboards, worked a treat. Mind you the rest of the boards were sound.

I also discovered when changing the bath that someone had literally bashed a hole in the floor under the bath when plumbing in the shower so I ended up putting the bath on two nice hefty planks and bracing the damaged floorboard and planks with a dirty great piece of angle iron - the nearest joice was the other side of the wall so I couldn't cut out the damaged bit there was nothing to sit a new piece on.

heresmo

Hi again Clunkclick.

Reading what you say and hoping I've understood, it does seem more likely that it's water dripping from person down the bath panel rather than wet feet and because weight will be on the foot area you mention, the water will gravitationally go that way.

Re floorboards, these are normally set into/under the walls, so you might need to buy "hangers" as you can only get one end in and under, not both, of course. Alternatively, you'd have to cut the boards across and abut the middles. Then you'd need a crosswise joist - or two, as it's usually better to stagger cuts in floorboards. This is where I'd read trundlenut's post again, though hangers ought to be an option.

Re the groove thingy, if the chipboard and floorboard (or replacement chipboard) is set on the joist, it wouldn't need to be tongue and grooved there, just butted, so would just need to take off the ickle sticky-out bit from the chipboard if it's pointing that way.

On old houses, there was an airbrick set in to air the underfloor cavity area, so important to try to keep air movement going another way in modern houses and enclosed bathrooms (e.g. window ajar, vents or fans). I'm afraid I can't agree with your thought that the boards were set too close (if I read you correctly) as you can't leave gaps in tongue and groove chipboard or over joists so airflow has to come from somewhere else IMO.

Again, me not know so will happily stand corrected. Just know from what I've found that previous peeps had done (What the...) and trying best to learn what fixes such things

Regards
Mo

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Clunkclick

Earlier this evening, I had a closer look at the damage, and I think I can get away with just replacing an approx 14" x 11" section, as all the board outside this area seems sound at present. This will leave a reversed "C" section of the existing undamaged board north, south and east of the hole. The easterly side will extend well under the bath.

The joists run across the line of the boards and the bath and the damage extends up to the piece of timber that retains the plastic bath panel at floor level. So the strategy will be to cut out a section of board, which extends north and south to the joist faces and east to the retaining piece. Fix bearer battens to the joists, extending suffiently east to connect with the middle of the undamaged "C" section and to fit a joist cross brace at the East and west joints of the new and undamaged old board.

I've got a spare length of flooring grade chipboard in the loft so I will cut a suitable section out of this, mount it on the bearers (Again spare timber), screw it down all round and give it a coat of varnish or PVA. Hopefully, gross cost of repair will be next to nothing.

I think I will then renew the plastic bath edging topside, after having re-caulked it. And see what happens.


Nick

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heresmo

Hmm... If you're interested in my views and again assuming I've read your post correctly.

I'd perhaps worry a little bit about replacing such a small area with chipboard, even if screwed in all round, though you mention a cross-brace, so hopefully it'll be supported under.

Have you got the right screws and brackets? Those black supascrews (wide thread) are good (easy) and don't rust, ditto solid brass ones (not just brass coated).

Is your spare flooring board the same depth? (Sometimes even chipboard is thicker in bathrooms). If not, an alternative might be to get an offcut of marine plyboard if poss or even just build up the depth with a small ply (e.g. 2 or 3 ply).

Re its getting wet, do you pick up the bath mat after use (e.g. hang over bath to dry)? Rubber-backed doesn't necessarily mean waterproof and moisture can get trapped under, especially if carpet is laid.

Anyway, sounds like a plan that'll work if the joists are sound


Mo

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Clunkclick

Thanks everyone for your advice and pointers - there are definitely some things there that I didn't think of.


Mo,
The spare board is standard flooring, 18mm deep, which is the same as the damaged bit. So I will cut the appropriate section from this length.
I'm a bit averse to using another flooring type such as ply for the replacement, in case its different characteristics e.g stiffness adversely react with the carpet when its folded back in place.

After rumaging through my gash bits and bobs, I've decided to use 1" square battens and 2" steel screws, with 1.5" screws for securing the board to the battens.

And, yes the bath matt is hung over the side of the bath when not in use. It usually goes through the washer once every couple of months, so there shouldn't be an mold problems there. Anyway the recovered bits of chip board didn't show any evidence of fungus/mold attack.

The existing arrangement has lasted 20 years and the planned replacement, with a coat of varnish, will be a little more durable - it will out do my period of tenure here !

The nature of the fracture was strange. The piece that de-laminated from the underside of the board was bigger than the extent of the damage on the top, by about an inch or so all round. ! Also, the edges around the bottom side de-lamination were not dirty, suggesting that these were the last to break and that the centre of the damaged area delaminated first. Eh ? I can only think that this would happen if the board had been bowed upward, as the hump in the floor suggested.

Nick.

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daiking

Bit late to this but I have had problems with a chipboard floating floor. The only thing I really wanted to add was that are grades of flooring specifically for wet areas (mine had a green hue)

Caberboard Product Range

Bloody things queaks and creaks like hell too.

heresmo

In the good old days, they would stop creaking which arises from boards rubbing over the joists by putting a bit of felt in between, or rubbing the joist with candle wax. Not sure why chipboard should squeak as theoretically, it woudn't expand and contract (so doesn't flex) as wood does though

There is another idea that it's better to use "twinned screws", so that instead of using one that could work loose by a board bouncing, one would put two screws an inch or two apart as "\.../".

Regards
Mo

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daiking

Floating floor 8' x 2' boards sat on 4" x 2" timber 'joists' with 2" of bog standard polystyrene foam in the gaps. 'Joists' sat across the concrete beams which are the structural floor of the building, afaik.

Not sure how or why it squeaks/creaks/groans but the bedrooms have parts of the floor that make a noise when stepped on. These are carpetted areas as well so its not the fault of laminate flooring.