Damp Problem

[Adam135]

Hi fellas, id be grateful if someone could give me a bit of advice with a damp cellar.

Long story short, old building with a closed cellar since built by a concrete floor. Concrete floor wood and steel support became rotten which meant it had to be replaced.
It was replaced with a wood floor which has become rotten again in 2 years while the building was closed. Due to no air and the cellar floor being left as bare soil.
Sharp sand, damp proof membrane and paving slabs were placed down.
The floor appears to be dry but the wall are a problem.

I understand the reason the wood floor had become rotten was due to condensation and a lack of air but as its completely underground its very hard to install any ventilation. I've recently got a heat recovery unit but I don't think its providing enough air as the cellar is rather large.

With 19" walls and approx 6 foot underground I cant work out whether its rising damp or penetrating, I think its both as the walls feel wet to touch.

I had one builder tell me to apply tanking slurry although he said he couldn't guarantee it which sounds off putting.
Any advice as to what needs to be done, or who I should call in order to find out what the problem is?

Appreciate any replies thankyou.

 

[Blagard]

The problem with a tanking slurry is that it can get blown off by hydrostatic pressure. If it doesn't then fine. But to do the job properly floor and walls need to be done to form the "tank"

The biggest problem then is the lack of ventilation. To get moist air out of the basement you will frequently need some form of mechanical ventilation.

As for the rotten floors I think you need to find out what type of rot it is and get it sorted out. Condensation might get the timber damp but either wet rot or dry rot will be what does the real damage. If dry rot then you will need a very thorough treatment to make sure it does not return. As noted below if you let a cellar get damp again even for a brief period any dry rot spores left will rapidly take off again, and so the cycle repeats itself. Despite the name Dry Rot needs humid conditions to get established and once you have it once it requires less humid conditions to restart - unless the treatment is 100% effective.

Even if you do a thorough job you could still find the cellar damp as they are notoriously difficult to keep in good condition. e.g. leave the ventilation off while on Holiday and come back to a stale and damp cellar!

 

[Adam135]

Thanks appreciate the reply.

I actually tried to tank one wall myself, this resulted in the wall staying wet with visible droplets on it. Im pretty sure i followed the instructions right but it didnt seem to work.

Having a quick read of wet rot or dry rot it seems as if there is both present, pretty sure the floor is mostly ruined and most likely needs replacing.

As regards to ventilation, I bought a small heat recovery unit which seemed to have no effect, could be because the cellar is quite large.

Its impossible to put in air breaks as the ground level is in line with the upper floor.
Just a hunch but If I were to dig a few feet down outside and put in windows for air would that help?
Thinking of how older houses have windows below ground level for cellars.

The thing that confused me the most is, the only part that has air bricks there is a metal beam directly next to the air brick which has droplets of water on it always even though it has air coming directly to it.

 

[Adam135]

I understand a dpc is applied above ground level.

The cellar walls are underground therefore the way to cure them would need either tanking slurry or membrane?
But how or what would be applied to the wood floor joists that run across the wall?
The joists don't go into the wall, they are attached to a wood piece that runs along the wall. This piece has become rotten presumably cause of the damp in the walls?

The floor will need replacing but what would need to be done to the walls?
i.e if it had a membrane or slurry would it be attached straight over this?

 

[Blagard]

If you are able to sort out the ventilation to the cellar you will have a fighting chance of getting an improvement (You may never get a cure for the dampness). You have said that you can't get air bricks in because the floor above is at the same level as the ground outside. But you do refer to an air brick. Is that all you have?.

The metal beam near the air brick is probably just cold and the droplets are likely condensation.

I appreciate you have mentioned digging down and putting in a window but it is not light you need but air movement. Lowering the outside ground level and putting in air bricks will help. You should be trying to create a flow of air through the cellar which at the best of times is very difficult because house cellars frequently have just one wall available to vent. Is that what you have?

So just focus on getting the ventilation sorted for now.

 

[Wakz]

Thanks for the reply.
I did try a ventalation unit but the air it provided didn't seem to have any effect.

It's a large cellar, it's a large detached building. The cellar is split into rooms, the room with only 2 air bricks is the smallest. These air bricks arnt enough to provde air for the whole cellar.

In regards to the window, the idea was to have a window for air although air bricks would do the same job. If i was to dig down I would need to install drainage I presume.

What would you recommend applying to the walls as I think they suffer fr penetrating damp as they are underground.
I understand they can be tanked or membrane but what would go on the wall where the joist is in contact with the wall?

 

[Blagard]

I have never used any of the face applied tanking solutions myself only sheet ones that are built in behind walls as a new building goes up. So while there are various ones on the market I could not say if they were any good or not.

The joist in front of the wall is a problem because there is nothing you can do to it regards tanking. It would have to be removed to apply tanking to the brickwork behind and then put back.

But unless you solve the issue of ventilation any other work is really going to be of very little benefit.

As you have indicated any pit outside (for window or vent) could just end up being a water sump unless you get the water away.

 

[Wakz]

Hi appreciate the reply.
Just had a local damp company have a look at the cellar, he said the main issue is a lack of ventalation. He has had a quick look and aid he would be in touch again, he said he was going to contact triton, I think they are a contractor.
Best way he said was to have air bricks or angled vents coming into the cellar.
I suggested the pit idea, he said they could dig about a foot length outwards and then dig downwards to create the pit.
I mentioned if I would need drainage to this he said it would be okay to fill te bottom with gravel which would make a soakaway for water.

I'm not too sure on this idea as would that not cause the water to run downwards and perhaps cause it to enter from the bottom.

Regarding the pit, would you say it will provide enough air? In other words will there be enough air going down the pit and in through the air bricks?

 

[Blagard]

Your damp man is referring to http://www.tritonsystems.co.uk/

An angled vent would be a good move - It needs locating to get the best circulation of air into the cellar.

Draining a pit with gravel could work if the ground is suitable. If it was in clay then probably no use whatsoever.

 

[Wakz]

It would be angled vents as this is cellar is large.
Where could I buy angled vents from? Would the ones screwfix sell do the job?
In your opinion would a pit provde enough air? As the air would have to travel down into the pit at an angle?

 

[Blagard]

Perhaps it would be better to look at stepped or snorkel types of vents to avoid a pit altogether. Seal all joints

Example:
http://www.dealclick.co.uk/product/13498885/Marley-Offset-Air-Brick-Duct-MV21-Black.html
http://www.ebay.co.uk/itm/Telescopi...-Air-Brick-Ventilator-Airbrick-/281244129635?

Personally I would try and get a vent in every 1.5M/2m of wall with one in each corner wherever possible.

 

[Adam135]

Would these angled vents provide enough air, bit unsure due to the bend in them would air be forced into the cellar?

In the picture of them, there shown to be attached to a wall that is only 1 brick thick/wide, as the property im wanting to put them on is much thicker than 1 brick, would these still be okay to go on if there was a gap between the vent and the outside air vent attachment?

 

[Blagard]

The bends will offer very little resistance to natural drafts so that will not be a problem. Use a plastic airbrick on the outer end of the duct to maximise the free area.

To get the bottom part through the wall you can just extend the duct, or you could build the whole Z bit into the wall.

Untitled

• Blagard
• 30 Jan 2014
• 1

Z duct built in

Untitled

• Blagard
• 30 Jan 2014
• 1

Sleeve extension

 

[Wakz]

Hi thanks for the reply.
Would the sleeve extension go in the wall or is that for making the vertical length longer?

 

[Adam135]

Couldn't edit that last post, Just to be a little more clearer..

Would the sleeve extension extend the air brick horizontally, so that the vent would fit in the wall?

Or is that extension for the vertical length going downwards?