Damp joists what should I do ?

[Gary111]

Hi I have a terraced house maybe 1930s , I can see the first couple of feet of joists from the front wall near the inspection hatch are soaking wet.
Doesn’t appear to be rotten , (I think it was also like this around 6 years ago when I bought the house)
It looks like maybe it’s had dpc injected from the drill holes.
Could it be condensation ? The air bricks seem small and there’s a concrete slab extension to the rear.
There are a couple of areas of pointing that look dodgy.
There’s a small area of expanding foam next to one of the joists under there too.
Also under the stairs near the back of the lounge can smell a bit damp.
Thanks

 

[foxhole]

Can’t see any damp timber? Are you sure it’s not a stain from a treatment ?

 

[Gary111]

Thanks for replying, it feels wet, water droplets on the underside here’s a pic of a section of floorboard from the hatch

 

[Gary111]

I have noticed a house further down has some different looking bricks a bit higher up, I wonder if they had a similar problem

 

[KenGMac]

Gary111, good evening.

You mention a rear extension with a concrete slab. Does this extension span the entire width of the rear elevation?

What can at times occur is that the concrete floor slab in the rear extension blocks of the rear air bricks [if fitted??] this lack of air flow front to rear under the floor can / will cause various types of damp issues.

Can you see any air bricks on the rear external walls at all??

As for the neighbours property, that row of air bricks is indicative of someone trying to get a load of air to circulate, i would bet that there is a rear extension on that property as well??

Ken

 

[Gary111]

Thanks for that I’ll check, it covers maybe 2/3 .

 

[bobasd]

"Can't see any damp timber?" - well unless you actually look, and know what your looking for you definitely wont "see any damp timber"
OP,
ignore the ignorant or you will pay hard cash to join them.

 

[bobasd]

"that row of air bricks is indicative of someone trying to get a load of air to circulate"

no its not - the "air bricks" are the "Holland System" of inserts. they have nothing to do with underfloor venting.
they were sold by scammers as a cure for rising damp, and have disfigured lots of houses.
they never worked and they never will.

OP,
there are two courses of historic injection holes below the Holland nonsense in the neighbour's wall.
which would mean that the neighbours have had or still have rising damp issues.

 

[bobasd]

OP,
try and find your DPC's, rake out a little mortar - perhaps there's a DPC below the air vent you show?
you need to replace all those metal vents with plastic double air bricks at about every 1.5m.

under the floor there's a massive amount of condensation showing on the soil surface, and under the T&G floorboards.
adequate through ventilation will relieve this - but you may have wet oversite soil? or even high groundwater?

the joist tails sitting in the brickwork are showing signs of rot -
you need to go under the floor, and probe all your joist tails including under the stairs, and round any fireplace hearth trimming joists.
look for softness and discolouration.
slide about on a plastic sheet.

the foam was possibly an attempt to firm the joist pocket up.
pressure injected DPC's in outside skins had a limited chance of success.
do you have interior signs of damp on the lower walls/skirtings?

sub-area's under hallways are always suspect for lack of ventilation and hence rotting joists - you need to access under the hall.

 

[Gary111]

Thanks Bobasd , I think the airbricks are ceramic but don’t look like they have much flow.

I dont suppose you are in the Manchester area ?
Or know of someone suitable there ?
Thanks

 

[JP_]

Toolstation airbricks are £1.79 each .... get a free workout and change them yourself! I actually found it really hard work - even with my cheap Katsu SDS drill.

Reminds me, I still need to fit mine - I made the holes and put the air bricks in place, still not got around to mortaring then in!

https://www.toolstation.com/9-x-3-air-brick/p70541

 

[Gary111]

Thanks Jonbey I’m not sure what goes on the inner skin of the wall ?
There are apparently peeiscopic vents that lead from the air brick and divert the air lower.
I wonder if that may work to vent under the floor better ?

 

[KenGMac]

Gary111.

Are there any airbricks on the rear wall? either on the original property wall or in the extension?

Any idea if the front air bricks are all clear of debris and rubbish?

 

[JP_]

There are apparently peeiscopic vents that lead from the air brick and divert the air lower.

I don't think needed if not there now - if the floor level is a couple of courses of bricks up and the air bricks directly under, then that would give enough air flow. My guess is that you just need more - or some are totally blocked. In my 1930s bungalow almost every air brick was blocked up, most painted over, some covered in a concrete path, in some the damp course had collapsed and was blocking most air flow, and in all there was a pile of dirt on the inside too - result - lot's of damp, rot and mould.

If you are planning to stay there, then the best thing is probably to refurb one room at a time, lifting all the floorboards, replacing any rotten wood, clearing out air vents, replacing air bricks, treating all wood with preserve (I used Everbuild Triple Action, kills insects & their eggs, protects against wet and dry rot) and insulating under the floor between the joists. And clear out any junk down there, as this will help trap moisture and reduce air flow.

My whole house smelt of damp and mould when I moved in, now no smell - well, a little in the last area I haven't done yet, but I've already removed some rot and left the floor partly exposed and ventilated. It's not what I signed up for when I bought the house, but rewarding to make the improvements!

This is how it started for me: https://www.diynot.com/diy/threads/my-rotten-floor-s.491659/

latest project: https://www.diynot.com/diy/threads/bathroom-project.527790/

and 2 other rooms in between those ... happy days!

 

[JP_]

in fact... Snorklevents! https://www.diynot.com/diy/threads/...tilator-with-solid-walls.493708/#post-4044160

I did consider it myself, had forgotten. Instead had the path dug out...