Wet rot in floor joists

[Saturn1]

Hi all,
New to forum - was unsure whether to post here or in flooring so hope I made the right call.

Would welcome advice re the following: have bought a terrace with a through lounge/dining room and there is evidence of wet rot to the floor joists at each end of the room and a need for re-doing the DPC. Have had two widely differing quotes and sets of advice re the flooring in particular. 1) replace entire floor in one go as if there is damp at each end of the room that makes the most sense 2) replace the rotten sections only up to the - is it called the sub wall? (a wall that runs across the division of each room) and treat the remaining healthy flooring with a fungicide spray.

Am wondering a few things here:
1) which makes most sense (the second option seems credible to me)
2) I have gone to professional damp companies so far but a friend recommended a carpenter who can do this and buy the relevant treatments as well - is there a reason to go with one option over the other? I was swayed initially by the 30yr damp guarantee for the works that the damp companies provide but the carpenter won't be able to I guess, but I am not sure if I even really need such a guarantee? Is it of any value for resale or anything do you think? Surely if the work is done to a good standard and the necessary treatment applied by a chippy that is enough?
3) if I use a damp company would you consider it necessary to use a PCA registered one or not?

I can't move into the property until the floor is done and there's such a financial commitment to it and range of costs I'd really appreciate your advice. Also, if done DIY/by chippy are there products that you recommend for the spray treatment of the good floor and for protecting the ends of the replacement joists. Other than that I simply assume it is enough to ensure replacement with treated wood?

Hope that makes some sense

Have tried a read of forum in other threads for advice so far but would really value some up to date advice on this specifically.
Thanks in advance

 

[^woody^]

The treatment of wet rot is not a specialist or technical job. Replace the rotten sections of timber and rectify the cause of the dampness to stop it reoccurring. That's all you need to do, and no chemical treatments are required. Water is the cause of the rot, so that needs to be dealt with.

Whether whole joists need to be replaced or just sections is a decision that depends on each job. If part replacement will give a sound sturdy floor, then there is no reason not to take that option.

The prevention of dampness getting to the joists is very important. This is done by a physical barrier at the joist ends where they sit on the wall (polythene wrap), or hanging the joists on steel hangers off the wall. Also specify treated timber (eg tanalised) with cut ends treated with a standard preservative.

If the sub floor needs to be ventilated, then make sure you have that job done too.

So yes, it is a basic carpentry job. You don't need no specialist treatments or company, but obviously whoever does the work must be competent.

 

[Joe Malone]

There is no point in replacing timbers that are sound so if replacing them as far as the sleeper wall does the job then that is all I'd do. Woody is exactly right, this isn't a particularly technical job and if you want someone to sell you an unnecessary retrofit damp proof course a great expense then by all means book a PCA registered company.
Simply employ a joiner to replace the timbers, make the timber is pressure treated and make sure he wraps the timber ends in a plastic boot if they are sat on brickwork. Improve sub floor ventilation by clearing vents in air bricks or installing additional air bricks. Make sure you have no water leaks in the floor void and if you do then get these sorted. You don't need any spray treatments at all.

 

[Saturn1]

Thanks folks. Really appreciate the replies. A chippy it is!