Wet floor joists..need to replace?

[Brown and Boris]

Finally got around to getting the damp done in the dining room. Full tanking jobbie as it is partly underground. All is going well. Contractors knocked off the plaster and suplhated the walls to deal with the salts yesterday. Today the guys applied the tanking system and they are back Monday to plaster. All going well. But..

It looks like I have soggy joist ends, but the good news is that they seem to be sitting on an inner lip so they don't need to be cut back into the walls when they are replaced. Anyway, I was quoted £65 to £90 a joist by the posh damproofing people to cut off about 600mm, and splice in new treated wood. There are 10 joists.

I have a damp meter which suggests the joist are indeed damp over 20% up to about 600mm (but not yet rotted and only the very ends are quite soft). After about 800mm, the moisture drops down to under 16%.

My question;

If I treat the existing joists with a good dose of fungicide and bug killer like Boron, and then simply fix lengths of new joist alongside the existing with steel or galvanised coach bolts, do I really need to cut out the old joists and spice in new ends as that seems a weaker fix? The joists are set on bricks with slate topping ( I know) so once the damp is stopped and I remove the damp muck that has built up betyween the joists so they are not touching anything, why do anytghing more? Splicing in new joist ends requires a splicing kit and another few feet of very fragile floorboards to be lifted to make the joint sound. Once the damp source is removed and the joist ends protected is there a massive risk of the new treated joists getting infected/wet by leaving the existing ones in situ?

They have lasted 240 years to get a bit soggy, if treated and allowed to dry, why can't they stay???

Edited by Brown and Boris on Friday 29th May 16:57

Edited by Brown and Boris on Friday 29th May 17:02

[MrV]

Professional opinion I would replace.


Personal opinion if they are treated correctly I would leave them in and just add new joists along side.


£600 to £900 sounds like a piss take for what is at most a days work for a chippy even including a labourer and any unforeseen problems.

[Mr Fenix]

Having seen and dealt with mouldy, rotten joists in my time I would recommend you replace/repair the joists as necessary.

However 900 quid is being bent over a barrel and savaged with a broom. 400 - 500 quid seems more like it (that's what I would've charged were I the contractor) anything more and I'd want to see a list of materials and labour costs.

[Brown and Boris]

Thanks guys. I have the materials now to do the job (about £100 including the timer, Boron, coach bolts, plates etc) and my chippy is coming anyway on the 8th.

I will see if the damp readings drop over the next week as the joists are open to the air and the damp gunk wil be out today. Got to be beter than I had either way as 3 joists were not actually connected or supported at all, they were resting in bricks so I will have to splice new ends there!

[ncs]

Timber merchant head on...

Not that long ago all timber for joists was 'wet' in other words it had a moisture content of well over 20%.

Only in the last few years has it nearly all become 'kiln dried' but even now KD timber can have a moisture content of up to 21% if I recall. The main difference is kiln drying it changes the cellular structure & if it does get damp it dries out more quickly, do you know how old the joists are?

Nick

[robinhood21]

240 years, at a guess.

[ncs]

robinhood21 said:

240 years, at a guess.

Oops...missed that bit!

fk it, rip em out & start again

As long as you buy treated joists & treat any cut ends your plan sounds fine

Edited by ncs on Saturday 30th May 15:57

[Brown and Boris]

ncs said:

robinhood21 said:

240 years, at a guess.

Oops...missed that bit!

fk it, rip em out & start again

As long as you buy treated joists & treat any cut ends your plan sounds fine

Edited by ncs on Saturday 30th May 15:57

I have treated timber ready for the new joists and have some more treatment on the way to be sure. I am alos treating the reclaimed floorboards which are going down along the 'wet' gable, just in case.

It looks now like the joists are laid on a solid sandstone floor and just held off the stone with packing (thick quary tiles and lumps of sandstone). It seems remarkably dry afte the first 2 feet from the troublesome gable wall and all the debris seems to be dirty sand, possibly washed down from the wall base or washed up from the sandstone floor. In places it looks like the joists have been cut THROUGH the stone and the trench through which it passes has filled with debris which I have raked out. Either that or a loose sand floor has solidified but I would have thought it would have washed to one end before it solifified. It is solid enough to need a chisel to cut it and one very solid lump was a foot square.

Anyway, bottom line is that having cleared all the debris, the joist ends are worse than I thought and the resting corners are pretty well shot, along with the bottom edges having lost some flesh in places where they have had their wet sand covering. It looks like I will have to do the full 'new joist ends' thing although the joists are hardly load bearing because they are laid, apparently, on a solid stone base all the way across. I had thought there had been a cellar but it may have just been a small understairs pantry cut into the stone to keep the food.