Dry rot in ground floor lounge joists

[billm]

As it is now, rainwater cannot run of it.

I assume that these headers are spanning the cavity wall ie; the cavity starts on the course above them ?

So if the rain can't run off them, and with the poor pointing, plus being headers, they have become saturated and are passing water through to the inside wall/floor etc ?

Ok .. I've just done a water test outside. I poured a full bucket of water in the corner (to the left of my last photo) and it ran along the wall to the right. When it got to the 6 or so bricks upto the airbrick, the water hung around right by those headers and seems to be draining under them into the house.

Now that tally's nicely with the 4th photo showing the inside of the same area. Its covered in fungus all around that area.

I think that's where the problem is. Those headers, especially to the left of the air brick, need pointing to keep the rain water out.

Does this sound right ?

 

[anobium]

billm wrote

I assume that these headers are spanning the cavity wall ie; the cavity starts on the course above them ?

So if the rain can't run off them, and with the poor pointing, plus being headers, they have become saturated and are passing water through to the inside wall/floor etc ?

Ok .. I've just done a water test outside. I poured a full bucket of water in the corner (to the left of my last photo) and it ran along the wall to the right. When it got to the 6 or so bricks upto the airbrick, the water hung around right by those headers and seems to be draining under them into the house.
Now that tally's nicely with the 4th photo showing the inside of the same area. Its covered in fungus all around that area.

I think that's where the problem is. Those headers, especially to the left of the air brick, need pointing to keep the rain water out.

Does this sound right

Can't be sure, but I don't think that the headers are spanning the cavity.
If anything, from what I can make out, they will only extend in as far as the other bricks.
By all means repoint as it can't do any harm and may well prevent moisture getting in.
A bucket of water is not the best way to simulate rain, try using a garden hose on the brickwork higher up the wall, (say a couple of metres) for a while, and then monitor the situation under the floor.
This should give you a better idea of were the moisture is coming from.

 

[JohnD]

those bricks look very much like the beginning of footings. I gather that there is no concrete oversite or slab. If you have the chance to excavate beside the wall you could see what the condition of the brickwork is like below ground. If the mortar has eroded it will be less resistant to water (as well as weaker). I wondered if it was lime mortar rather than cement?.

As well as repointing, it could be worth laying fine concrete on the exposed top with a slope to shed rainwater and prevent it lying on the bricks where it will soak in. If this is done at the same time as the repointing it should knit together well. You could increase the number of airbricks at the same time.

I don't know how deep the cavity will extend below the dpc, you may find it is solid brickwork or filled in with concrete below ground level.

 

[billm]

I'm now looking at the damp patch on the side of the chimney breast. The fire isn't used, hasn't been for many years although there is a vent at the bottom to allow air flow upwards.

I've knocked the damp plaster off the surrounding area to reveal damp(ish) bricks and mortar.

The hole on the right is where the joist sat .. and the wood is fine, no rot
The hole on the left is where I knocked out to check if there is a cavity that needed emptying. There isn't. Just a very small 1/2" gap between the bricks as you can see.

Should there be a DPC on this chimney breast wall at the same level as the other walls in the room ? I can't see that there is one.
Could this have failed or be missing / need replacing ?

Any ideas ?
thanks

 

[anobium]

The hole on the right is where the joist sat .. and the wood is fine, no rot
The hole on the left is where I knocked out to check if there is a cavity that needed emptying. There isn't. Just a very small 1/2" gap between the bricks as you can see.

I'm a bit confused, is that the chimney breast on the left of this photo , where the marble hearth is.?
It doesn't look right , could you take another photo to show all the wall head on.

Should there be a DPC on this chimney breast wall at the same level as the other walls in the room ? I can't see that there is one.
Could this have failed or be missing / need replacing

Again difficult to say for certain.Needs another full on pic to be able to comment with any degree of certainty.

 

[billm]

Ok will take some more photos and post them saturday pm.

thanks

 

[billm]

Here's a front view of the fireplace. I'm wondering if the damp could be coming up from the footings under the front face of the fireplace and working its way to the right side of the chimney breast to where the damp patch showed up on the plaster. If this is the case, then the front of the fireplace wouldn't show the damp because of the marble hearth ?

 

[anobium]

Thats much clearer, quite honestly I wouldn't bother trying to form a dpc round a chimney breast, it's well nigh impossible because of all the rubbish that is used when forming the base.
You don't appear to have much of a damp problem in this area, and all I would do is replaster and encase the end of the joist that you have removed in a dpc .
On another point you appear to have cut back the joists from the opposite wall, beyond the sleeper wall, why?

 

[billm]

Ok thanks I'll do that.

I cut the joists mid-way on the sleeper wall so that I can butt joint the new ones against them with both ends supported by the wall and bolt timber either side of the joint to make them solid joins .. a bit like the old fashioned splinter when you had broken your leg. Probably the photo makes the cuts look out of place.

To be honest, the remaining timbers are only 2m long so it might be easier ( and possibly the same ££) to just put new lengths of joists in full width .. it'll save on the jointing, coach bolts and the splinters. I'll ring around this week and get some prices.

Should I use plain un-treated timber joists, soak the ends and brush them with Cuprinol 5 Star or buy ready treated (green ?) joists ? I'm thinking that the ready treated ones will be alot dearer and when I cut them I'd still have to put Cuprinol on the cut ends.

Oh .. and the reason for the rotten joists on the kitchen wall ? blocked cavity. It was solid with brick bits and soil .. 2 bricks worth over the dampcourse .. full length of the wall. So looks like it had been that way from the 30's when they put the original solid floor in the kitchen and bunged up the cavities. Hence the previous repairs.

 

[anobium]

You didn't need to cut them mid way on the sleeper wall , you should have let them fly through, ie beyond the sleeper.
What I would do now is let the new joists go beyond sleeper by about 200 mm and then bolt them to existing using 12mm dia bolts and bulldog connectors.
Pre treated is better because of greater penetration of fungicide but as you say you will still have to treat cut ends.
Costs of pretreated used to be about 10% more .
Blocked cavity sounds right but I would still check your underfloor ventilation.

 

[billm]

Oops .. i cut them short ... never mind ..

I've added another air brick where all the fungus was .. so that should increase the ventilation.

I've also floated mortar over those header bricks on the outside in a wedge shape, pointed them as well and added waterproofing liquid to the mix to hopefully make them more waterproof.

I've also scraped the top of the subsoil out of the floor and when all the brickwork is done I'm going to spray anti-fungicidal proofer on all the brickwork and the subsoil floor.