Removing suspended wooden flooring

motch

Hi Peoples

I live in a 1900's terraced house and i'm thinking about completely removing the suspended wooden flooring and cross beams (and floor supporting walls! etc) in one downstairs room to gain extra room height.

I'd gain about 4 feet, making the new height about 12 feet! Room is about 12 foot by 14 foot.

I'd like to know if the single 3 foot high brick walls crossing (which help support the wooden cross beams) are in anyway structural to the building?

Also would i need any planning for this? after all i'm not trying to add any more rooms, just making it higher!

there's a few reasons/different ideas why i'd like to do this (i'll try to add some more info about it all soon) I might confuse everyone too much if I add everything now lol

just trying to get some views and ideas about it all..

latecomer

The small walls should purely be support for the floor joists but it might be worth employing a structural engineer to check out what you are proposing.

No idea whether you would need planning or not.

One thing you will definitely need to check is where the damp proof course is on the walls. You couldn't go below this serious changes.

Mojisola

We have just removed our floors and put in insulated concrete floors. The house looked very odd at the inbetween stage. You'd have to have steps down into the room. You would certainly be below the dpc so that would cause problems. You would need to maintain the airflow under the floorboards to the other downstairs rooms or you would get problems with damp under them, too.

You will probably find that there are pipes and wires running under the floors and they would all have to be rerouted.

motch

cheers for the replys so far.

I'll try and add a bit more detail and background.... I've lived in this property for over 10 years now. It was converted from a four story house into two maisonettes about 25 years ago.

I have the lower two floors. It's arranged as an upside down house - ie two bedroom's on lower level, with kitchen, living room, bathroom above.

One bedroom has a solid floor (which keeps warm), the other with the suspended flooring has always been cold and draughty and a bit damp (smells damp)

About three years ago i removed the old carpet and sanded and varnished the lovely wide old floorboards, looks great! but noticed floorboards a bit rotted around edges, especially near the
outside wall. Damp smell improved a bit but still there.

Several months later I pulled up some floorboards near window and went underneath the suspended flooring (bit spooky at first! lol) crawled around a bit and noticed only one airbrick on
one wall, with nothing on the opposite wall/s so no through flow.

I'm thinking when the place was converted perhaps the builder put a solid floor in the other room, therefore blocking off any through flow? also the chimney brest has been blocked over on
the lowest level, probably for 25 years - maybe this was the original through flow? There's a fully working chimney fireplace on my room above.

27col

I had this problem with my first house. There was a 3ft drop below the boards. The whole of the floor was rotten with dry rot. There were only a couple of air bricks and no way there could be any significant air flow. What was required was to fill the space so that the volume was reduced to a quarter of its original size. This gave the air bricks a chance of ventilating the space. The walls you mentioned are called sleeper or dwarf walls and are there only to supply support for the floor joists. Depending on the span there may be 1, 2 3 or more of them. Easy enough to remove, they are in no way structural to the house in general, except for the local floor that they support. If the floor is to be removed then they have no more purpose.

motch

Mojisola wrote: »

We have just removed our floors and put in insulated concrete floors. The house looked very odd at the inbetween stage. You'd have to have steps down into the room. You would certainly be below the dpc so that would cause problems. You would need to maintain the airflow under the floorboards to the other downstairs rooms or you would get problems with damp under them, too.

You will probably find that there are pipes and wires running under the floors and they would all have to be rerouted.

Mojisola did you gain much height and if so how does the room look now?
I could fit some steps down from the hallway without too much trouble. + i'd try to add some storage underneath in them.
I don't have any other rooms with suspended flooring so no need for airflow.

I have a single electric cable for a twin socket running across the crawl space, but could be re-routed with little hassle. no pipework luckily! (will be careful when cleaning out dust and rubble though in case i find some!)

Biggest hassle - I think -would be dpc as it stops a few inches below floor.

David_Aldred

Hi Motch,
The function of the intermediate walls (dwarf or cross sleeper walls) is simply to support the suspended timber floor joists at their mid span otherwise larger section floor joists would be required.

The damp proof course (dpc) as you rightly point out is normally under the floor joists at some point in order to protect the joist ends from rising dampness.

When you install your new solid floor ideally the damp proof membrane (dpm) beneath the solid floor would be sealed into the dpc in the walls to give one complete barrier to ground moisture. If this is not possible / practical then you need to structurally waterproof the area below the dpc with a design function of holding back moisture (be that penetrating dampness and / or rising dampness) and any salts within the wall.

Be aware that if you change from suspended timber floor to solid floor with a damp proof membrane you will reduce evaporation from the area of the floor and consequentially there will likely be an increase in moisture to surrounding walls below dpc level and at the new floor / wall joint. This increased moisture may find any weaknesses in the existing dpc.

Depending upon floor design there is also a likelihood that the new floor will move seperately to the surrounding walls over time and as such there needs to be a system in place that will maintain a waterproof flexible seal at the junction of the solid floor damp proof membrane to the wall structural waterproofing system such that the structural waterproofing system should ideally be continuous to the floor / wall area and be able to cope with such movement.

The solid floor should be compliant with the Building Regulations and a telephone call to your Local Authority Building Control Officer to discuss the matter is a first recommendation. They are usually helpful and can provide appropriate specification of works.

Furhter details on providing waterproof areas below dpc level may be found from the following:

Safeguard Chemicals - Redkiln Close , Redkiln Way, Horsham, Sussex, RH13 5QL (tel 01403 210204 ) www.safeguardeurope.com

Wykamol Group – Unit 3, Boran Court, Network 65 Business Park, Hapton, Burnley, Lancashire BB11 5TH ( tel 0845 4006666 )
www.wykamol.com

Sovereign Chemicals – Park Road, Barrow-In-Furness, Cumbria. LA14 4QU ( tel 01229 870800 )
www.sovereignchemicals.com

Hope this helps - kindest regards David Aldred Independent damp and timber surveyor