How much floorboard can be unsupported at edge of a floor?

[Lower]

I'm currently replacing a section of my lounge floor where the floorboards have started to rot due to blocked underfloor ventilation. I am also sorting out the ventilation issue to prevent the problem reoccurring.

Due to the installation of a set of double glazed doors leading to a conservatory, the gap between the edge of the last floor joist and the door is now approximately 6". The ends of the floorboards are therefore hanging in space by this amount.

I've currently replaced them as is and screwed them down but they squeak when walked on. I obviously need to support them but how much unsupported board is going to be acceptable?

Supporting them is going to be difficult due to the remains of the original wall that is still in place and supporting the door threshold. I'm currently thinking of screwing a section to the edge of the original joist to provide support closer to the wall will suffice, but the question is how much support do i need to give?

 

[aveatry]

I think I know what you mean I had the same thing.
Isnt your doors on the outer of the two brick walls.
So you can lower the internal one and do as you say add a short bit of joist to the origional one. - coach bolt side by side and sit the end on your now lower internal wall. This is what I have done as my joists were supported at the wall on bricks that came out of the wall (corbold I think ) I also built another support pilar of bricks under that joist in the crawl space, with a small bit of DPC under the wood. You need to get that bit solid as that door part is to get all the foot fall.
I am also in Leicester by the way

 

[big-all]

are you talking planks or chipboard and how thick

are you sure the next joist hasn't suffered ??

 

[Lower]

We're talking planks at 20mm thick but not tongue and groove.

The joist is parallel to the wall, sitting on sleeper walls, so it's only the ends of the boards that are hanging in space by around 6".

The joist is slightly soft in places, but only slightly. It's a short span between the chimney breast and the wall and I may yet replace it anyway but it takes screws quite happily and takes my weight without bounce so I think it's ok.

Unfortunately I can't move the joist any closer to he wall. It's already close to the remains of the wall and I need to put in an air brick behind it so moving it closer to the wall will hinder the airflow. I can bolt something to side of the joist, but it can only be around 2-3" from the top.

The doors have been fitted to he outside edge of the wall but the walls are solid rather than cavity. Bricks have been cut down to he level of the blue bricks and those bricks are in such a position I don't want to disturb them.

 

[aveatry]

think I get it now
between your joist and wall - drop in 6inch long noggings (or whatever is the exact length needed) screw through your joist into the noggins end (one end) the other end will be tight up to your wall.It all this 20mm down from the joist height and get some more of your 20 mm plank and lay it across - making kind of a shelf which will support your floor board overhang.Your noggins should not move there and you can pun in as many as you thing good

 

[big-all]

if you cant do as aveatry says the very least you should do is a minimum 4ft length but as long as possible minimum 3x2" at the end off the the planks screw into the planks to distribute the load sideways

this wont stop the joist sagging but will remove the bend on the individual planks

 

[aveatry]

The joist is parallel to the wall, sitting on sleeper walls, so it's only the ends of the boards that are hanging in space by around 6".

His joists run the oppsit way to what you are thinking-- hence he can not move the joist closer to the wall as that may inpeed the air flow fom the newly installed air brick

 

[big-all]

The joist is parallel to the wall, sitting on sleeper walls, so it's only the ends of the boards that are hanging in space by around 6".

His joists run the oppsit way to what you are thinking-- hence he can not move the joist closer to the wall as that may inpeed the air flow fom the newly installed air brick

i think the joists are running paralel to the wall but 6 inches away is that correct
or is my description clear as mud as usual

 

[Lower]

The problem is that the the wall has been cut back above the floorboard level and only in the centre where the door is so even if i removed the remains of the wall in the centre where the door is i would be prevent from moving the joist closer to the wall by the rest of the wall that is in situ either side of the door.

My intention is to bolt another section of wood onto the existing joist, but only to a depth of 2-3 inches and only to fill the gap where the door is an the ends of the floor boards overhang.

The question is how much floor board i can leave overhanging without problems. At the moment there is some flex in the 6" or so of floor boards that are unsupported and because it is in front of a door it will be a high traffic area.

I am going to improve the ventilation with an air brick/hole and associated duct in a trench under the conservatory floor, but i want to avoid any contact between any wood work and the walls as it will inevitably take a while for the wall to dry out.

 

[aveatry]

If you go with my noggins idea the contact on the wall can be managed with a bit of DPC betwix the wood and wall
Did you have air bricks there befor that have been blocked by the new conserv

 

[Lower]

If you go with my noggins idea the contact on the wall can be managed with a bit of DPC betwix the wood and wall
Did you have air bricks there befor that have been blocked by the new conserv

Your noggin idea would work. Particularly as the other end of the noggin could rest on the wall where its been cut down below floor level as long as i put in some DPC as you say.

I think there was ventilation before the conservatory went in because the underfloor is otherwise very well ventilated with even a 4" bore cast iron pipe running from the corner that abuts the solid floored hallway to another room that abuts the hall way on the other side of the house. I've now got to cut a trench in the conservatory floor to put in a duct or a couple of drain pipes to reinstate the ventilation.

Would have been dead easy when the conservatory floor was poured but a pain in the backside now....

 

[aveatry]

The builders who did the conserv were cowboys for not maintaining the air.
I have just had building work done and the air flow was maintained vis brown sewage pipe before the concrete sub floor was layed.

Maybe you should also think about insulating your pipes too as that will be cold air under your conserv floor