Ventilation under floorboards

[jezztri]

Hi,

Hoping that someone can help.

My old Victorian ground floor flat smells very damp and various other smells. My damp survey advised of a PIV system, which I installed, and although it provides nice fresh air, if I sit on the floor I can always smell something.

I was going to replace my carpet for floor boards, but it has occurred to me that I may not have proper ventilation underneath the house. Although I can see vents on all sides of my property, they look to be higher than the actual level of the floors. It looks like when they cemented and did work around the building they have made the ground higher. Also, when they put the damp proof course in, they may have blocked it.

How can I tell, and who would I need to get out to identify the issue?

I am a single female and always need to get about 10 quotes for anything before someone doesn't quote me some ridiculous amount. For instance, this week I had a leaking roof with water penetrating a side wall. Quotes ranged from £200 to £1000! I obviously went with the cheapest option, and the guy even did extra work with repointing the chimney.

Thanks, for reading!

 

[Burnerman]

Just a little more info if you please.....
When you lift your carpet, what do you find -timber floorboards or concrete?
From your description it does seem like the property floor was originally suspended timber, in which case the air bricks were there to ventilate the void below.
Perhaps now it is concrete? No problem with that, so long as there was a polythene vapour barrier put down first!
John

 

[jezztri]

Thanks, for your reply John.

It is floorboards underneath the carpet. Underneath the stairs, the previous owners lifted up some floorboards to provide more ventilation I am told, so I can see they are suspended floors. What this means is that when I open the door under the stairs, I get smacked in the face with the damp smell, which is always worse after some rain and it begins to dry out. Definitely can't see any vapour barrier.

 

[Burnerman]

Right then!
If you look down into the void below the floorboards, you'll see that the property is built on earth (really) or a concrete raft.....on both situations you won't see the polythene vapour barrier whether it's there or not.
On an old property, built on earth is the norm, but of course the walls are built on footings - again perfectly normal.
Now then - those air bricks must ventilate the void below the floor boards......chaos will result rot wise if they don't.
The bricks, so long as they are below the floor level, will be ok so long as they are clear so do check that.
On earth floored buildings you have to expect a musty smell - that's the way it is, but I'd like to see a few boards come up, near to the outside walls preferably, to see that there is a damp proof membrane between the small sleeper walls and the floor joists themselves.
At the same time, you may see light through the air bricks too.
John

 

[ree]

A ground floor flat with a roof leak? Do you own the property?

Below your floor boards is a space: the crawl space, and the ground that you would crawl on is the oversite. In a Victorian property there would have been no concrete oversite, merely soil.

You describe a classic situation where, when it rains, the soil oversite is becoming damp, or even wet in severe cases. This damp soil will create condensation. Your oversite is, perhaps, much lower than surfaces surrounding the house?

Ventilation is the key to remedial action - so all your property air bricks at DPC level must be cleaned out from inside the crawlspace, or at least blown thro from outside. Thro ventilation will now clear the stale, dank air.

Besides thro ventilation: across the whole of the earth oversite its best to loose lay a polythene, or similar, oversite vapour barrier. The vapour barrier will contain the moisture in the soil.

Given that the difficulty has been noticed for some time, it might be in your interest to have the joists (esp joist tails in wall pockets) checked for fungal infection.

Why was a remedial DPC inserted?

Why dont you post external pics of the air bricks, the inserted damp course, and the raised surface levels?

 

[jeds]

Thanks, for your reply John.

It is floorboards underneath the carpet. Underneath the stairs, the previous owners lifted up some floorboards to provide more ventilation I am told, so I can see they are suspended floors. What this means is that when I open the door under the stairs, I get smacked in the face with the damp smell, which is always worse after some rain and it begins to dry out. Definitely can't see any vapour barrier.

Follow John's advice. You need to get a good look under the floor to see what is going on. You might be able to do that from the removed floorboards under the stairs or otherwise have a board or two taken up elsewhere. In Victorian houses there are usually a few cut boards that have been previously raised for plumbing or electrical works, These will be least fuss and mess to lift again if you can find them. Start looking near to plug sockets or where pipes disappear beneath the floor. If the space is tight a good tip is to use a digi camera - stick it under the floor and snap a few shots until you get one in the right direction.

Your problem will most likely be lack of sub-floor ventilation or alternatively it could be excessive moisture. Check the ventilation first; make sure your air bricks are clean and clear and are actually venting the sub-floor. When you look under the floor try to establish if there is a continuous path of cross ventilation from one side of the building to the other. You might need to lift more than a couple of boards to be sure. You never know what you'll find. I've often come across insulation (or newspaper) stuffed into sleeper walls and air bricks to stop air flow - by people who wanted to stop cold draughts. If you find anything like this it needs to be removed. Sometimes the original air bricks are just not sufficient and adding more might solve the issue. But work out the problem first before deciding what to do.

If all this is good then the problem might be excessive moisture. This could be caused by a high water table, poor drainage around the house or it could be a cracked drain or a defective water supply pipe or just a defective plumbing pipe. What are the surfaces around your house - hard or soft? And does it slope? Photos would be useful.

 

[jezztri]

Thanks, for everyone's reply. I've taken the tape measure out and it looks like the ones in the bedroom are just sub-floor.

The ones under the bay window and side of sitting room do not seem to be.

In response to the question about DPC - the previous owners I guess had mould, damp issues and instead of increasing ventilation they closed everything up further.

I'll need to get a camera down because my entrance and the ground outside are on the same level, with no elevation, so I can't see how vents could be situated sub-floor.

The only floor boards that are lifted are under the stairs so I'll have to try and get a camera down there, as don't really fancy crawling through. I can already see that a lot of building materials was dumped down there.

 

[jeds]

The vents don't always match up with floor level. Sometimes the brickies just left out several bricks on the inner face below the vent and the floor in a sort of telescopic configuration. Bit difficult to describe but I see it all the time. But it does need to be checked to be sure. Try to get some photos beneath the floor - a picture paints a thousand words.

 

[jezztri]

I've also posted some photos to:

My Albums Link: //www.diynot.com/network/jezztri/albums/

Yes, it does look like my oversite underneath the floorboards goes down another 60 cm below my entrance ground level and I have a slope going down into my bay window. So i guess that is how water is getting in + no ventilation because vents are above sub-floor?

 

[jezztri]

I've just posted photos of my subfloor as well. Is it meant to be this filthy? Looks like it was used as a dumping ground. No wonder it stinks!

 

[jeds]

It's not supposed to look like that but many do - although it doesn't look that damp! It looks too tight to be getting in and having a crawl about under there so if you are really determined to get to the bottom of this you are going to have to lift boards in strategic positions to get a really proper look under the whole of the floor. If you've got fitted carpets that's going to be disruptive.

The alternative is to sort the vents out anyway and hope that solves the problem. They don't look great so they need doing anyway. I'd get a quote to have them thoroughly cleaned and checked to see where they go and also maybe fit a couple of extra ones. It's difficult without being able to see it but it should be obvious to an experienced builder if this is possible.

 

[Burnerman]

I've certainly seen worse than that, and wetter too....
Give us a pic of the sleeper walls if you can, so we can look for any DPC, and secondly, how many air bricks are there in each wall?
All the crap down below is typical.....expect old cable and electrical fittings, lengths of copper pipe, sawdust, joist ends and copies of the Sun
John

 

[jezztri]

John - I had to google what a sleeper wall was!

I can only access the subfloor in the middle of the flat under the stairs, so can't take photos of the external walls where damp proofing is unless I pull up carpet and floors.

The previous owners passed on the paper work of damp proofing being carried out, amongst other warranties etc. Although the DP company they used is no longer in business! Also, I can see on internal walls where they have had to re-docorate and they have not done a very good job as I can see where it ends mid-way up the wall.

I think I may just have to bite the bullet and get a builder out!

 

[jezztri]

There's a air brick a metre a part in the front sitting room, and two in the bedroom that allows airflow from the front to the back. no side ones in the bedroom.

I suspect I should also check the next door property given that it is a semi-detached to see what ventilation is like there?

 

[ree]

The pics show a bone dry oversite & timber - as far as they show.


Quote: "It looks too tight to be getting in and having a crawl about under there" - what nonsense. This idiotic "advice" then goes on to suggest lifting boards up & down the flat, although "its going to be disruptive with fitted carpet." Is he being serious? There's probably an access hatch under the stairs. Why not have a look?

There's massive room to crawl & work down there. The rubbish thats written on here by people who have obviously never worked on the tools or crawled a floor is laughable foolish advice.
What next: "dont crawl you might get dirty"?

OP, thats often the condition of oversites - most of that rubble would be bricklaying rubble from the original build. Professional, skilled people, dont even comment on such conditions - they just get on with the job. Those copper and steel threaded pipes were run by someone working under the floor.


From your pics here's no sign of penetrating water, although, in another area, it might be - someone has to crawl & inspect the house, its that simple. Dont go pulling boards up.