Another Damp Question...

[jsmee]

I've trawled through loads of posts on this topic which have been valuable, but I have few specifics and would appreciate any advice out there pls.

1. Damp coming into a bedroom through an external wall. The wall is extensively covered on the outside by a climbing plant (Virginia Creeper I think). I think I know the answer to this one, but before I break the news to my wife that the plant needs to come down, is this likely to be a major contributory factor to the damp on the the inside of the wall? Also, the inside wall has been covered with some sort of polystyrene. Presumably this needs to come off as well in order to increase moisture evaporation?

2. The ground floor of the house seems to be generally quite damp (birthday cards 'curl' at the edges within a few days of being put out etc.). The cause of this is almost certainly coming from the cellar below, and I do have a long-term plan to increase ventilation etc down there, but with the imminent arrival of a new baby I need to do something more immediate. Would a dehumidifier be appropriate in this case? Is there a risk of 'over-drying' the structure of the house by removing too much moisture?

 

[Nige F]

1....cut it out @ the root plants are for gardens.2...any closed off old fireplaces that can be opened ....I seriously wouldn`t use a de-humidifier with a new baby around .......bloody things dry out my 50 year old throat

 

[jsmee]

Thanks Nige, although 'Plants are for Gardens' might not cut it as a justified reason to rip the thing down; it does look nice with the autumn colours and covers up quite a few scars, cables on the outside of the house. Anythng more substantive which supports the case that it could be contributing to the damp problem on the inside?

 

[diy_darren]

Is the plant climbing on the wall itself or a wooden frame? If it's on the wall itself it's probably preventing air getting to the bricks it covers.

Try and get a look at the brickwork the plant covers - check for damaged bricks or pointing. I have no idea what a virginia creeper looks like, but it may be damaging the brickwork in it's attempts to climb.

Don't be afraid to cut the plant back and pull it about a bit to get a good look at the brickwork behind it - it'll grow back!

 

[JohnD]

If you were willing to pay the cost of a dehumidifier, you could get twice the results for half the money by improving ventilation of your cellar and rooms. You need to have vents along each side of each wall, so that there will always be a through-current of air in the cellar. if there are existing airbricks, clean them out and remove any obstructions. You could do with a double-brick (9" square) every two or three metres of wall length for the cellar, and one in each room if you have tight-sealed replacement windows and no fireplaces.

If there are not enough airbricks, and you have not got time and energy to cut out more, you can hire a Core Drill from your local hire shop. this will easily cut a 105mm or 110mm hole through a brick wall. You can then add grilles to keep out mice and things (this size is used for tumble-drier vents etc so is readily available). if it is a cavity wall you can sleeve it with a piece of plastic soil pipe, mortared in round the ends. You can get the covers in reddish brown to tone with bricks or light grey, but you can paint them with non-drip gloss to blend in with your walls. You can get a cowl with anti-draught flap for the rooms, but do not use them in the cellar as they prevent air ingress. Never use the covers with a sort of venetian blind flaps as these rattle annoyingly, and fall off in high winds.

 

[jsmee]

Thanks John - there are certainly some possibilities for me to drill a few holes and I will follow your advice. The main problem here is that the previous owners built an extension along the full length of 2 walls at a level higher than the top of the cellar; that leaves me with no possibility to introduce ventilation in the part of the cellar which is worst affected by damp without some extensive digging through concrete. Although a dehumidifier might cost me a few quid, I guess this might be the more cost-effective solution for a quick fix in this case?

 

[jsmee]

Darren - sorry to split this discussion into 2 topics; should have done that in the first place....

The climber is not attached to a frame; it's attached itself directly to the unrendered stonework. On first inspection, the attachment appears to be mostly superficial, but I'll take your advice to look closer at the joints etc.

My concern here is that as the plant completely swamps the entire wall, and leaves it in total shadow throughout the entire summer, any moisture that is within the stonework is prevented from drying out?

I'm starting to sound like I'm answering my own question here

 

[JohnD]

Might be possible to run ducting into the damp part of the cellar. You can use plastic, not expensive. You will need at least one "in" and at least one "out" duct, run to opposite sides of the house. that way there will almost always be airflow. Ducts should be high up as water vapour is lighter than air, so it rises. You could experiment with extractor fans on the ducts. If you introduce negative pressure in the cellar it will prevent water vapour spreading up into the house.

It is also possible to lay a new concrete floor in a cellar, on top of dpm, this will reduce damp from the ground (but it will stil come through the cellar walls. The concrete is required to stop water lifting up the dpm and floating it away.

 

[jsmee]

Interesting.... I hadn't thought of ducts. I could certainly run one from a window in another room in the cellar to one end of the damp area, and then drill a few holes in the wall at the opposing end of the room.... What would be the principal here? If I duct air from window height to the top of the room which is affected by damp, this would mean an incline of about 2m. What dimension of duct would I need? Presumably the larger diam. the better?

 

[JohnD]

I'd use 100mm-ish (soil pipe size) as it is readily available, as are bends and wall-clips to fit, and not very expensive. Fan companies sell plastic duct in shorter lengths, usually thinner and more expensive. proper ventilation co's make galvanised steel ducts, usually rectangular in section, wrapped in insulation to prevent condensation.

If you needed to double the flow, I'd use two 100mm ducts rather than try to find a bigger one. You can probably clip it to the ceiling where it will be relatively out of the way. it will go through the wall using one of the holes you make with your core-drill.

If this is an old house with chimneys you can open them top and bottom and they will improve ventilation and redice damp.

 

[jsmee]

Great, thanks John; I'll get onto it. So you don't think that the incline the air would need to travel 'in' from window height to ceiling is an issue? I also forgot to mention the significant fact that that this particular window opens into a light-well which acts as a soakaway (very damp..). I might need to duct up out of there as well.

 

[JohnD]

can't you core out into the open air above ground level? that would be better and there is more likely to be a breeze.

 

[jsmee]

Yep, that could be possible. Thanks a lot

 

[jsmee]

JohnD - unfort. not as straightforward as I'd hoped. Although ducting could be easily extended to the damp area, it would involve two 90 degree turns and a hight drop of 2m and then a height gain of 1m. The house took a glancing blow from a WWII bomb, and there's quite a bit of stone reinforcement down there that I need to get around

I could still do it, but i was wondering if your reason for diverting me away from the dehumidifier solution was purely a financial one. If I reverted to this course of action, would it help, and could it present a risk of 'over-drying'?

 

[JohnD]

I saw the dehumiifier as expensive, and not such a good and practical long-term solution as ventilating the moisture away. You will have to keep doing it because more moisture will keep permeating the walls and floor. You may need a pump to dispose of the condensate.

Add as much ventilation as you can, and see how much it helps. If you have a "dead air space" you could use mechanical extractor instead of air cross-flow.

If you have a damp unsealed floor, consider laying new concrete over a dpm.