water under the house and condensation - help!

[hawie]

Hi

Please can you help?

We live in a 3 bedroom bungalow which we have had for just over 2 years, build in 1960's. We have had really bad problems with condensation in the winter since we moved in - affecting all windows and to the extent that the floor boards in lounge have rotted under the french windows.

We have ventilation bricks under the floor boards, and have recently had vents put into every room. This has helped a bit, but we still have condensed on the windows in the morning and it smells musty - its much worse the colder it is. We have recently pulled up the floor boards and there are 2 inches of water underneath the lounge floor - under the rest of the house the ground is wet but not pooling.

SO far we think the problem is due to the water table - its very wet around here and the garden is a bog in the winter. We are thinking about putting in land drains to take try and divert the water away, and then insulating the floor boards to keep any residual water out of the house.

Can anyone help?

Thanks

Hawie

I am very concerned as I have a baby and there are black mould spots growing on the walls - I am worried about his health

 

[anobium]

If as you say it is due to the high water table, your chances of removing completely or diverting the water are low.
Your best bet is to increase the underfloor ventilation by either additional or larger airbricks. If your current airbricks are 75mm replace them with 150mm.
Alternatively if they are already 150mm insert additional vents between the existing.
From what I recall the building regs used to stipulate 1 airbrick for every 2.4m run, but this should be increased if you live in an area with a high water table.
This will prevent the moisture vapours on the oversite from condensing and affecting to a lesser extent the rooms above.
You say that you have had vents put in every room, are these in the floor or skirtings,? if so all you are doing is extracting the moisture vapours from the oversite into the rooms above.
Removing condensation is a process of elimination starting with most obvious and working along.
One of the biggest factors I used to come across particularly in bungalows was were the owners had blocked of the fireplaces.
Its amazing the affect that it had on the removal of moisture vapours.
Good luck.

 

[^woody^]

It might help if the OP describes the rest of the construction, insulation, ventilation, heating and heating patterns too.

It is very unlikely that the sole (or even main) cause of the problem is the underfloor water

 

[anobium]

It might help if the OP describes the rest of the construction, insulation, ventilation, heating and heating patterns too.

It is very unlikely that the sole (or even main) cause of the problem is the underfloor water

Take your point Woodie, but as I said to the OP start with the obvious, and in this case rotten floor, water on oversite, equates with underfloor condensation.
A bit pointless embarking on other measures until this fault is rectified.
It may well be that other factors are contributing to the problem but all to often in my experience householders are often talked into needless expense without knowing what is the real cause of the problem.

 

[^woody^]

Yes, there is nothing wrong with damp or even standing water below the floor. Any evaporating moisture will (should) be dealt with by the vents.

If there was an issue with high humidity below the timber floor then there would be a high probability that there would be associated rot or problems with the timber floor first, before there was a condensation issue within the rooms above.

If the floor timbers are OK, then there is a good chance that the floor void is adequately vented, and therefore the condensation above floor is unrelated.

 

[anobium]

Yes, there is nothing wrong with damp or even standing water below the floor. Any evaporating moisture will (should) be dealt with by the vents.

If there was an issue with high humidity below the timber floor then there would be a high probability that there would be associated rot or problems with the timber floor first, before there was a condensation issue within the rooms above.

If the floor timbers are OK, then there is a good chance that the floor void is adequately vented, and therefore the condensation above floor is unrelated.

This is what the OP wrote-

affecting all windows and to the extent that the floor boards in lounge have rotted under the french windows

 

[^woody^]

I took that as condensation running down the french doors which are sitting on the floor - which would be in line with what has been described.

 

[hawie]

Thanks for your input

We have vents under the suspended floor and vents above floor level into each room in an attempt to increase ventilation. We have double glazing, cavity wall insulation and insulation in the loft.

The bungalow is brick built, on a suspended floor, and is 'link'detached to the bungalow behind. There are approx 30 bungalows in the surrounding area - all have similar problems but are the lucky ones who seem to have it the worst!

The floor under the french windows has rotted due to the water running down, through the carpet over a long period of time. We have removed the carpet, put in a piece of wood and wipe down all the windows every morning to try to reduce the moisture.

We had an electric fire in the lounge - we have unblocked this and put in a gas fire to try and increase ventilation - so we are trying to improve things but its just so frustrating.

We discovered that the joists under the dining room are wet as it appears that the path way outside the house is higher then the floor level - its a complete nightmare and I wish we'd never bought it!

Any advice appreciated

 

[anobium]

Can you clarify the vents comment, ie are you referring to vents in the wall outside or are you saying that you have some additional vents fitted in the surface of the floor?.
Also when you say the joists are wet, is the dampness on the ends of the joists were they go in the wall, or on the underside of the joists.
PS a pic may help

 

[blackpoollad]

i also have had a similar problem the joists and floorboards in my bay were rotted and i have replaced them but also have water under my house apparenty its down to high clay deposits but i only have one air bick which is half covered by the idiot who had the house before me so im having more air bricks installed and have been told by a builder friend this will fix it.

 

[PerryOne]

The first thing to do is dig a hole in the garden and ascertain how high the water table is.
If the water table outside is lower than inside then a French drain round the bungalow will help, to lower the water, if there is somewhere to drain the excess water too.
The surface of the French drain should be six or more inches below the damp proof course.
It the outside path is up against the bungalow wall then the French drain may be finished with pea shingle or slabs as you wish but, keep the slabs away from the outside walls.

The rotten floor caused by condensation running down the French doors, is covered.

While the water laying under the floor may look a disaster, if it lays below the damp proof course then, it does no harm, that area would be damp and cold anyway.
The insertion of air bricks under the floor, will not do anything to help the damp situation.
It is unlikely that any surface water will evaporate in a situation where the water is cold and still and much lower than any circulation due to wind suction through the air vents.
Any water vapour in the air will automatically make its way to the nearest cold surface, that is the damp walls.
The floor boards and joists, will be warmed by convection and radiation from above, and as such being above ground water temperature there is little chance of them becoming damp as may happen if you decide to insulate between the joists. Having said that, you write that the joists under the dining room floor are wet? The wet floor in the lounge we have covered, could the dining room floor be wet from the window? Or do the joists run into the outside wall where the garden path is above the damp proof course?
Summing up, water below damp proof course level is not a problem.
Where you have apparently added air bricks above the floor level, all this will do is make the home impossible to keep warm at reasonable cost and these should be filled in.
An electric fire is kinder to a home than an open gas fire, an electric fire produces dry heat, where an open gas fire will add more moisture.
Usually, damp is put into a home by people.
Living our normal lives, breathing and sweating adds a lot of water vapour to our homes. Children and animals being more active add more vapour than adults. Not having extractor fans in kitchens and bathrooms, or not using them, or leaving doors open all add water vapour to a home.
Turning heating down at night or off causes more damp problems than anything else, warm air holds much more water vapour than cold air and when warm wet air meets a cold window or wall then the water vapour turns into condensation.
Not closing blinds or curtains in the evening helps to keep windows warm and condensation at bay.