What are these vents underneath the house for

CarPark2

I am looking at a house with a view to buying it.
There are two things that I found unusual:
1. It has wooden floors, but on the ground floor, it doesn't feel like the floorboards are resting on concrete. It feels like there is a hollow underneath the floor boards.

2. There are vents on the outside of the house, just above ground level, but below the level of the floor (there are steps up to the front door). See picture:


Does this mean that there is a cavity underneath the house?
What is the purpose of such a cavity?
It seems like the kind of place that would attract rats. Is such a house construction likely to cause problems?

Thanks in advance.

Gumbo

1. Most likely a suspended timber joist floor.
2. Vents to allow air circulate around the timber joists so they can breathe.

CarPark2

Thanks for the quick response.

The house was built c. 1998. Does that fit with suspended timber joist floor?

What is the purpose of a suspended floor, as opposed to just laying it directly on concrete?

Is this likely to be a problem in terms of
a) rats/mice/slugs etc.?
b) draughts?

jca

My father's house is like that. Floorboards laid across dwarf walls. He had a major roof leak last winter requiring all the carpets to be taken off the wooden floors. With the floors uncovered it's a draughty spot, he never had trouble with rats etc.

loyatemu

we have the same - it can be draughty if you have the boards exposed, it is possible to insulate underneath but tricky to retrofit (though if you're completely renovating the house you could do it at the same time). Suspended floors are very common in older houses, we've never had a problem with rats, but I've heard one of the neighbours say that they did.

BryanF

The vents indicate a suspended timber floor. It is essential this ventilation remains insitu.

Rubberchikken

We have these plus the wooden floors in our house (circa1956).
The original floorboards in the sitting room are in great condition (no dry rot etc).
Definitely have never had an issue with rodents.

rawn

Had that issue in a house i rented before. The floors were FREEZING and we had mould growing up our walls. It turned out the floors were designed as you described but were missing a certain layer (i can't remember what they called it) which meant all the floorboards would have to be ripped up and the layer placed beneath them. I would get a contractor to look at it. We had a small problem with mice but the house was empty for months before we moved in so it may have been a coincidence

Moonbeam

I have it under my house too.
It is timber framed and apparently lacked enough ventilation and firebreaks the builders had to come back after some of the house were found to have dampness in the frames.
We had them at the front of our houses after.

L1011

Moonbeam wrote: »

I have it under my house too.
It is timber framed and apparently lacked enough ventilation and firebreaks the builders had to come back after some of the house were found to have dampness in the frames.
We had them at the front of our houses after.

I thought you lived in the same, very much concrete construction, development as I did? Which has these, because of suspended timber floors

Gumbo

Moonbeam wrote: »

I have it under my house too.
It is timber framed and apparently lacked enough ventilation and firebreaks the builders had to come back after some of the house were found to have dampness in the frames.
We had them at the front of our houses after.

Timber frame houses are typicall built off ground bearing concrete slabs, not a suspended timber floor. Are you sure your thinking of the same thing?

Moonbeam

L1011 wrote: »

I thought you lived in the same, very much concrete construction, development as I did? Which has these, because of suspended timber floors

I do I also own another house .

Looking closely at pics of both they do look different.

foggy_lad

CarPark2 wrote: »

Thanks for the quick response.

The house was built c. 1998. Does that fit with suspended timber joist floor?

What is the purpose of a suspended floor, as opposed to just laying it directly on concrete?

Is this likely to be a problem in terms of
a) rats/mice/slugs etc.?
b) draughts?

These timber floors are an alternative to the concrete floors in many houses. with carpets and flooring they can make for a very warm house but if the boards are left bare it can be draughty. There should be no more/less rodents than in any other house.

BryanF

I have a 60year old suspended timber floors, I lifted the the timber floor boards, put a breathable membrane sagging between joists, insulated between, and put a vapour control layer/air-tightness layer on top taped & sealed, and put back down the floor boards, sanded & clear vanished. No drafts, no sign of rodents, external walls vents still ventilate the subfloor.

CarPark2

BryanF wrote: »

I have a 60year old suspended timber floors, I lifted the the timber floor boards, put a breathable membrane sagging between joists, insulated between, and put a vapour control layer/air-tightness layer on top taped & sealed, and put back down the floor boards, sanded & clear vanished. No drafts, no sign of rodents, external walls vents still ventilate the subfloor.

Thanks. Do you mind me asking how much that cost and what floor area it covered?

CarPark2

foggy_lad wrote: »

These timber floors are an alternative to the concrete floors in many houses. with carpets and flooring they can make for a very warm house but if the boards are left bare it can be draughty. There should be no more/less rodents than in any other house.

Thanks. Are they more common in older houses? Everyone that has given examples above seems to be talking about much older houses.

Also, based on my experience with decking and a barna-shed, I thought that rodents love spaces underneath buildings, as it gives shelter and protection. If they find a way in to such spaces they quickly establish home there. Am I missing something?

loyatemu

CarPark2 wrote: »

Thanks. Are they more common in older houses? Everyone that has given examples above seems to be talking about much older houses.

Also, based on my experience with decking and a barna-shed, I thought that rodents love spaces underneath buildings, as it gives shelter and protection. If they find a way in to such spaces they quickly establish home there. Am I missing something?

apart from the vents the rest of the subfloor space is walled-in well below ground level, so difficult for vermin to get in unless a vent is broken.

CarPark2

loyatemu wrote: »

apart from the vents the rest of the subfloor space is walled-in well below ground level, so difficult for vermin to get in unless a vent is broken.

Thanks. Are the joists typically laid on top of concrete, or is there just soil under the joists?

jca

There are dwarf walls built into the space under where the wooden floor is going to be. The joists are then laid across these walls and the floorboards on top of them. I hope I made it clear enough. As someone said earlier the space is impregnable to rodents etc unless a vent gets broken.

CarPark2

jca wrote: »

There are dwarf walls built into the space under where the wooden floor is going to be. The joists are then laid across these walls and the floorboards on top of them. I hope I made it clear enough. As someone said earlier the space is impregnable to rodents etc unless a vent gets broken.

Thanks for that explanation. Just for clarity, below the dwarf walls is it just soil, or are they built on a surface of concrete?

Gumbo

CarPark2 wrote: »

Thanks for that explanation. Just for clarity, below the dwarf walls is it just soil, or are they built on a surface of concrete?

There is normally no concrete.
The walls are built in foundations as normal and then the timber floor joists span between the walls.

Jen44

my house and my parents house both have floors like this. We never had rats in either house! both houses are in the same estate built around 1950's 60's