Old suspended floor question.

[Pallando]

Hi - we have just started an extension/renovation project. House is currently half Victorian and half 80's extension. The downstairs Victorian half has suspended Wooden floors, and we frequently get slugs in that room (and on one memorable occasion a road!).

My question is, when we get to that room, should we strip the floorboards and insulate between the joists (adding in a breathable membrane), or should we replace the floor with a concrete one? I am guessing that the slate damp proof course is probably not entirely effective which might affect the decision!

Cheers!

Toad. Not road!

lift the old floorboards and have a look to see why it is damp. Cure the source of water. It might be a broken drain or water pipe. No doubt the numbskulls who laid the concrete floor in the extension blocked the ventilation of the airbricks on that side of the house, but that would not cause toads and slugs.

Once you have rectified the source of water, improve the subfloor ventilation and you can have an improved wooden floor.

An old house that has had the old floor taken up and concrete tipped in is a sign of an unresolved water problem. Often the water makes its way up through the concrete or the walls, as it is still present, and is much harder to find and repair when buried under a hundred tons of concrete. If the water source is cured then there is no need for concrete.

p.s.

slate lasts about a hundred million years. Sometimes there is a crack in it, but that doesn't cause toads. Most often it is bridged by numbskull builders or gardeners. Chemical injection does not repair numbskull bridges, nor leaking pipes.

Thanks! There are currently no drains under that floor, and we are planning to completely replace the heating system, so hopefully any leaking pipes will be redundent then anyway. One of our builders has said that our ground level is too high on one side of the house (just below dpc), so we need to sort that as well (will probably drop the level and patio rather than soil).

Any thoughts on adding a breathable membrane to keep the slugs out?

very often the drain gullies and rest bends on soil pipes are broken beside the house, especially where it was in a town or city that experienced wartime bombing, or if built on clay that moves about. If you dig a hole near them you may find red worms. You may find there is patched concrete around them to hide the sinking wet ground. This is just next to the house wall so may easily get into the void under the floor.

The water supply pipe probably runs from the stop-cock next to where the front gate used to be, under the floor to where the kitchen sink used to be, when the house was built.

Thanks again.

The one soil pipe we have does not go under that floor, though there is a water pipe feeding the kitchen (which will be redundant eventually). Currently the floor does have airbricks to the front and back of the house, and we will put pipes in from the back ones to the edge of the extension we are doing to keep the air flow.

My best bet is that the soil levels were too close to the air bricks, and there was a leak in next doors chimney which might not have helped. Will wait until the floorboards are up in that room before deciding what action (if any) we take.

Oooh - can I jump in? I also have a suspended wooden floor and have caught a couple of slugs in the sitting room (pretty grim). It sounds like you are lifting the floor as part of a larger renovation, but I'd be interested to know how you are going about it. I need to replace the flooring in that room (the laminate has popped up) and need to check whether the old floorboards / a joist has warped because of damp. Are you just ripping up the old floor covering and boards to look at the joists / subfloor? If so, who are you getting in to do it and how long will it take?

if you have slugs and bulging laminate, you have excess water. Most likely from a drain, providing the slugs with food.

Look for a yard gulley that your sink drains into, or a soil pipe.

In an older house it is normal for these to crack and leak under the ground, when the downward pipe turns to run horizontally. This is close to the house wall so detritus easily gets in. If you dig a hole and the ground is wet with red worms, you have a drain leak.

Thanks Piglet! I had the drains surveyed before I moved in so I'm hoping it isn't that, but I do know there aren't enough airbricks under that part of the house. Is there a chance it's condensation in the subfloor?

lack of ventilation will prevent it drying out, but where's the water coming from?

Has the ground been raised, or sloped so that rain runs or pools against the house?

Are the gutters and downpipes leaking? Are the radiators? Is the house built on a pond or riverbed?

Is there a water meter?

Taking up some floorboards will enable you to take a look and a sniff and perhaps see what's going on.

I'm sure no vendor would nail down laminate flooring to prevent you seeing and smelling the damp. Would they?

Ha - good point Piglet! No sloping ground / pond etc - there were leaking gutters when I moved in which are now fixed. No water meter as yet, although I'm pushing Thames Water for one, which should show up any water leak.

I'll just have to have a look underneath. Given that it's a terrace I suppose it could even be coming from a neighbour....

Hi Diplobrat!

We are having a rear extension and also doing alterations to quite a bit of the old house. The suspended floor is in the original victorian house and is currently a dining room and kitchen - we will be taking out the dividing wall (with steel) and turning it into a sitting room, but it will be several months before we get there!

First thing to do is to take up the carpet and see what we are dealing with underneath that. I do want to try and create a barrier for the slugs (as well as making sure the floor space is fully ventilated!).

Hallo Pallando!
What did you find, and what did you do in the end?
I have a 70s house with suspended wooden floor , wooden joists with pine floorboards and good air bricks that we are going to remodel.

The worst thing I have found at 3 am, on my kitchen floor, is not the odd little slug. Once I nearly puked when I found a massive spider wrestling with a massive leopard slug. Both about 1 1/2 inches across. It was so freaky because it was this really intense, but obviously totally silent fight. I think I was a bit tipsy too. Not ideal.
The only source of wet I can think of is if my over enthusiastic watering of pots on patio outside had made it more attractive to slugs- but the slugs are found on both sides of the house, including a no pot zone that I really don’t think has water about. I had thought they were coming in to eat 🤢

I would love to hear about anyone who has changed a suspended wooden floor. Ideally I would pull up the planks and insulate, then some underfloor heating and tile on top, but I think that is thought of as liable to fail because of -
Difficult to insulate but not block air bricks underneath, therefore risk of mouldiness Developing.

• timber underfloor unable to take a weight of screed for wet underfloor heating system.
• risk of tile lifting if underfloor system not laid right.

Perhaps a dry ufh system is the way forward here?

-that is- maybe a dry ufh on top of existing wood floor, is way forward? What do you think?

I think you should start by looking under the floor to find the source of the water, and repairing it.

Hi IgletPiglet. We haven't got to that room yet, so still haven't looked under the carpet. According to our builder the ground level is too high, which might be encouraging damp. We are going to try lowering the level when we put a patio in at the back.

Thankyou Pallando and PigletJohn. Not looking forward to discussing need to look under the floor with OH! Or the builder! But I appreciate your consistent advice PJ.

Pallando, that’s encouraging that your builder thinks he has id the problem from the ground level. Pigletjohn, if the ground level is thought to be prob, would you still look under the floor?

yes

the subfloor should be well ventilated, and also, there should not be sources of water. Leaking pipes in the ground are quite common in old houses.

Update on the floor!

When we took up the layer of tiles in the old kitchen we found vinyl, then quarry tiles coated with bitumen, then sand and then earth. The walls in the old kitchen look like they have been injected and then had bitumen put around the sides as well. Two plastic soil pipes were in the earth tin an attempt to provide an air flow. This has now all been dug out and a new suspended floor installed!