Joist rotted floor dropped.

[Leasu]

Hi there.

I've spent the past year renovating a mid terrace 1905 3 storey house and am starting work on the final room (back downstairs room)

The floor needs some serious work doing as it's not level any where. The plan was to lift the floor, level then insulate. I was lifting some floor boards today in an area where the floor seems to have dropped down from the skirting board. Wish I hadn't lol.

There seems to be some rot on one of the joists quite far into the room. I am struggling to tell if its wet rot or dry rot.

The previous owner had block paving laid in the yard which meant the outside floor height was much higher than the inside floor so I'm assuming damp had been getting to the joist ends. The outside is now rectified.

There was also only one airbrick in the whole of the property to the rear (where this rot is) I have since had more put in to the front to increase air flow.

I did notice the joist ends which sit in the external wall seemed damp on the joist showing the rot.

Any help advice would be awesome and much appreciated.

Leanne

 

[Deleted member 174758]

It matters not if it's dry rot or wet rot - you'll still need to cut the joist back to approximately 1 metre beyond the last rot point and sister the joist. The new joist end should over lap the old one by at least 1 metre (better still 1.2 to 1.5 metres) with a minimum of three M8 or M10 coach bolts fixed through on centres of no more than 600mm and fitted with star washers (also called dogs) between the two timbers (to prevent slippage). Because the new joist end won't align with the original pocket you'll either need to brick-up the old pocket and cut-out a new one (in which case the repair joist really must be treated timber and the end wrapped in a breathable membrane), or alternatively you'll need to brick-up the existing pocket and fix a new treated timber ledger plate to the wall using resin anchors (if the masonry is at all suspect) or possibly Rawbolts. The new joist is probably best fixed to the ledger using a metal joist hanger and I'd be belt and braces about this and put a piece of DPM between the wall and the ledger because for the sake a copperds you give the ledger extra protection

Dry rot is pretty widespread in old houses round here. It produces a cracked appearance on the surface of the timber and may need treatment, although getting air flow working and removing (and burning) the affected timbers is the recommended approach on small areas. Wet rot causes discolouration and the fungal "bloom" is often white in colour. It's not uncommon in wet parts of the world to find timbers with both types of rot, in addition to boring beetle damage

 

[Munroast]

can I see a photo showing where the rot is relative to the wall or any structure it is sitting on ?

My guess is that it is wet rot or has been wet rot. If it was dry rot I think you would see some growth like a mass of roots on the wall and fruiting bodies that look pretty much like fungus.

If it is or was wet rot then just replace the timber and keep it away from moisture with some damp proof membrane or by removing the source of damp and that is the job done. If it is dry rot - then good luck, it's nasty stuff and you will need specialist advice

 

[Leasu]

Thanks for the replies guys. Much appreciated. I'll post some more pictures when I get more of the floor up.

I did ring up rentokil and Peter Cox to have an inspection but they charge 130 quid just to look at it. I've contacted some other companies that do a free survey/quote so will find out what they say. I hope it's just wet rot because I'm so skint and dry rot looks a nightmare/expensive to rectify.

 

[Deleted member 174758]

AFAIK you can never really truly eradicate dry rot - it's in the environment but it can also seemingly stay dormant in lime plaster and mortar, etc for years and then, when the moisture level of the host material goes up to the right level it will start up again. Best solution is to get the ventilation working properly, cut-out and burn infected timbers and about a metre back from the affected areas and sometimes to treat any areas where the filaments were with a suitable toxin. I believe red diesel can be very effective, and cheap, if somewhat smelly (and boy does it linger)

 

[bobasd]

leasu, are you still out there?

search for "rotted floor joists".

thats not a ledger its a sill plate, built-in when the house was built.
ventilation needs to be through air bricks at the front, rear and any gable walls.
set the air bricks 1.5m to 2m apart.

the sill plate needs to be completely removed in alternate sections, and replaced with (semi-dry, small stones) concrete packing.
all new joist tails need treating and capping with DPC material.
depending on the length of the span it might be worthwhile replacing whole joists instead of doing bolt-ons.

fwiw, dont use "red diesel" or anything else thats flammable below your floor - spray and treat with the recommended chemicals only.

 

[Leasu]

Hi guys I'm still here. Had someone come out and take a look today. Was only here 5 mins, put a moisture meter in the joist and said they are dry so it's dry rot. 500 quid to spray the room that the joists are in or 1300 to do the whole of the downstairs. The guy said it would protect my joists from wood worm too.

Im not fully confident in that report, so am trying to get someone else to take a look. Could this rot be old wet that has since dried out??

There is no mushrooms, the floorboards to the eye look absolutely perfect on the underside where these joists have the rot. Surely if it was dry rot there would be miles more damage? And spread much further. ??

I've added some more pics that I managed to get today.

One way or another I'll get the job sorted but I don't want to fork out money if I don't need to as im struggling as it is.

 

[cdbe]

My first house was very similar with numerous areas of rotted joist ends. I declined the offer from the preservation company (who I think were working in some kind of "partnership" with the mortgage company) to spray the timber at a cost of £500 (this was 25 years ago) and instead stripped back and replaced all the rotten stuff with new treated (which the company would have charged extra for) and liberally coated it all with "Cuprinol 5 star complete wood treatment" I also cleared out the blocked airbricks. 25 years later the floor is as solid as a rock.

The Cuprinol cost me £65 for a 25l drum at the time, it's now £36 for 5l at Toolstation but well worth it.

 

[bobasd]

OP,
you could post pics of the whole room and external views of ground level and walls?
you could also remove the skirting and look for any issues behind it?
maybe you'll use the search button?
the damaged joists need repairing or replacing.
spraying is useless for lack of ventilation or timber earth contact.

all off-cuts of wood should be removed from the sub-area.
any chimney breast in that room?

for info. dry rot is sometimes called a posh name in Damp and Timber surveys - sepula lacrymans.
with lacrymans meaning tears - ie wetness.
or perhaps damp companies are referring to what happens when customers get the final bill?

 

[Leasu]

Thanks for all the replies.

I have also done a fair bit of research on the forum using the search feature.

Behind skirting boards are fine.

I've also found a blocked up air brick where the door step was and have now 're instated it so have a total of 5 air bricks rather than just one originally. Some nice air flow now.

I've lifted a few more boards and found an old lead pipe coming from outside which is capped off in the hall way. Lone behold it runs right where the rot is. Guessing there could have been a leak here at some point in the past. See pic.

Other joists look and feel absolutely solid so my course of action is going to be... remove and replace rotten joist, treat all joists with the cuprinol treatment which was mentioned above and relay floor.

The wall plates are all solid too.

The 2nd pic shows the room from a different angle. The broom is on the joist that's rotten.

Back to lifting these boards. Boy is it hard work.

 

[bobasd]

still no pics of the exterior?

have you recently had a DPC installed and Remedial plastering in that room because i can see fresh plaster - with a tide mark - and an empty bag of Thistle?
you need to open up that blocked fireplace to allow the chimney flue to be swept, and then install a permanent vent for through ventilation of the flue.
you've got four joists sitting in the hearth/chimney breast - are the tails sound? like all joist tails seated in wall pockets they should be treated and capped.
do you intend to leave the hearth in place or dig it out and board over?
from what i can see, a number of joists look dodgy - do you dig deep enough with a sharp, small screwdriver when looking for rot?

you should search here on Floors forum for lifting T&G boards without destroying them. no need for heavy work or splitting T&G's.
the wall to the right is the outside wall so all boards against that wall need lifting and pics posting.

the pipe is a 3/8" lead gas supply presumably now redundant, and previously used to supply a gas appliance or device - remove it completely.

 

[Leasu]

Hi Bob

Exterior pic uploaded.

Ends of joists all seem ok. Really tough and don't look or feel rotting.

The room was replastered about 3 months back.

The exterior wall was cladded with tongue and groove wood to a height of 1.7 meters if I remember correctly. This was fixed to the wall on batterns. Think the previous owner had damp many many years ago due to the yard been too high. I removed the wood which wasn't rotting but had a lot of black mould behind it around a year ago.

The fire place was bricked up around a year ago also. So that would need a vent? I was going to dig the heart out and board over yes? Is this a bad idea?

With regards to the joists, I'm thinking about just replacing them all now, while the floor is up. Sweet talk dad to borrow me the cash

 

[bobasd]

the deck is a foolish, unnecessary construction to have:
1. its possibly blocking off a fair bit of ventilation to whatever air bricks you have on that back panel of bricks below the living room window.
How many air bricks are below the window?
2. its raised the yard surface allowing moisture and splash to soak above any DPC line - including your neighbour's kitchen rendered wall.

does the kitchen have a solid floor?

the flue - maybe all your flues - will probably need sweeping and through venting.

dig the hearth out and drop the surrounding fender wall bricks to ground level. then board over.

keep all sound joists no need to ditch them.

for info: there's lots of advice on diynot for removing paint from brickwork.

 

[Leasu]

Thanks. Some good points there. Can the chimney vent be placed under the floor? Or will that interrupt the sub floor ventilation. ?

Believe it or not I've had the yard lowered a fair bit. The previous height was inline with the door threshold.

There is a 6 inch trench between the wall and the decking as well as the neighbours house.

Kitchen floor is concrete.

 

[bobasd]

have the flue vent on the face of the c/breast if you intend to have the opening blocked as it now is.

so the only airbricks at the rear elevation are below the window - still dont know how many or what size they are?

ground level in line with the threshold was way too high - it would never have been built like that.