Damp floor at patio doors

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While investigating my damp problems I have turned my attention to the patio doors. I have made as good a drawing as I can although exactly what is underneath the internal floor is a bit of guesswork from squeezing cameras down the side!


The top of the floor isnt damp but feeling underneath to the suspended floorboards and the joist they are very moist. It looks like the small joist near the external brick is the wettest. I squeezed my phone down the edge of the floor and this is a shot along the gap between the two joists above the inner bricks (cavity on the right hand side)


This seems to connect the internal wooden floor directly to the external bricks - I see no sign of any damp proofing although I suppose there could be a thin membrane between the joist and the external bricks?

It is quite an old set of doors, some of the double glazed units are misted but was just planning on replacing those units. Where the opening in the wall has been made for the doors and the cavity at the side closed I can see a vertical damp proof membrane so there must have been some consideration of damp at the time. No knowing if the wooden floor was done at the same time though. I know the floor should probably come up for further investigation but was hoping that would be a last resort as it is going to be a right pain to get up!

I have lifted some of the decking timbers outside as that looks very suspicious of causing damp problems to me. The "shim" I have labelled looks like a botched attempt to lift that end of the decking to make water run away from the doors so I suspect the previous owners have had these problems for a while. I am tempted to get rid of the whole deck anyway (just small children around makes it a desireable softer surface than block paving)

Maybe I just need a builder to come and have a look at all this!
 
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I've got a a feeling that removal of the timber decking may just solve your problem.
Looking at your drawing, with the joist fixed onto the external wall skin, water shed from the door rainwater drip would possibly soak the area around the top brick course. This of course could, and most likely would, wick through to the joist, causing the exact symptoms you have stated...pinenot :unsure:
 
thanks for your thoughts, I might do that as a first step and see what happens. I have already lifted a few deck boards further along the wall where they blocked an air brick with the deck joists and there is another one I can see is blocked which needs uncovering.
 
ok, ripped up half the boards and removed the joist up against the wall, there was quite a bit of wet dirt between the wood and the bricks and you can see they are quite damp in the picture (I guess it is hard to tell how wet the brick is inside though?)

 
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And no dpc? and is some pointing required above the air brick.
The big thing is maintenance of an air flow for ventilation at all times, no timber fixed to the external walls and a dpc between between abutting surfaces and timber to brick etc...pinenot :D
 
most of the house needs repointing actually, something I need to get done this year. The bit near the airbrick I scraped quite a bit out to see how bad it was - should I do a temporary patch of this until I get round to getting the rest of the house done? This pic is from a couple of weeks ago when I first uncovered that airbrick...

View media item 56503
 
1. Have you crawled under the floor?
How do you know what the detail is on the sub-floor side?

2. The decaying wood in the pic will have to be removed - it is beginning to show fungal decay.
The cavity filling appears to be quite high, this could be blocking the vents - see below

3. The paving appears to be blocking the vent (s).
Do you have sufficient, fully exposed, and correctly sized (9 x 6) vents in place?

4. Where is the external DPC - which mortar course?

5. It would be possible to open up below the doors, and remedy the detailing, but if you intend to replace them then watch and wait.
 
1. Have you crawled under the floor?
How do you know what the detail is on the sub-floor side?
No I cannot get under the floor as the whole floor is secret nailed solid wood planks which I am trying to avoid ripping up and replacing, I think this might be unavoidable though! I have taken off the skirting which has given me camera access, and could also poke the camera through some gaps in the wall from underneath the adjoining room but it is a bit of a guess.

2. The decaying wood in the pic will have to be removed - it is beginning to show fungal decay.
The cavity filling appears to be quite high, this could be blocking the vents - see below
noted

3. The paving appears to be blocking the vent (s).
Do you have sufficient, fully exposed, and correctly sized (9 x 6) vents in place?
The vent you can see is the size of one brick - nothing is being blocked. I guess this might have been a bigger vent that was replaced when the paving was laid? On the internal side of this vent there is a big hole in the wall with cavity wall insulation partially covering it which I have manually moved out of the way - that was dry. There is a similar brick sized vent on the other side of the patio doors which is also covered by the deck which I will uncover asap. There are larger (original) vents on the front of the house.

4. Where is the external DPC - which mortar course?
This I am unsure about! How can you tell if and where the DPC is? This is a 1930's semi and I dont see anything different in any of the courses - should I be able to see some kind of layer in the mortar?

5. It would be possible to open up below the doors, and remedy the detailing, but if you intend to replace them then watch and wait.
I think we'll see if anything changes over the next few weeks now some air is getting to the area.
 

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