Joist issues (w/pics)

[markwm]

Had a look under the floor board in a 2u/2d terrace. There's 2 cavities, one under the hall and one under the living room.

A couple of the joists in the hall seem to have rotted at the ends, it's not that bad but I can dent the wood with my fingers. Time to repair?

I'm more worried about the white stuff I can see under the living room. Not sure if it's some kind of mould or spiders webs/nests??? Someone previously has propped up the joists(2 years+ ago I think) and just stood un treated software in damp earth.....

 

[Nemesis]

Ectoplasm?

 

[Ian Bond]

Are there any airbricks providing ventilation to the voids?

How soft is the timber - can you easily stick a screw driver blade right into the centre of the joists, or is it just the surface that's affected?

And are the joist ends rotten where they bear into the walls?

I wonder why someone propped the joists like that - was the floor sagging, or too 'bouncy'?

You are obviously concerned enough about something to be lifting the boards.

May be better to support the joists with brick or masonry piers instead of softwood, and use pieces of dpc to isolate the wood from the piers.

Having said that, my house has a Victorian bodged floor that's survived pretty well without rot. They ripped out a stone flagged floor and built the suspended timber floor with the joists resting on rough stone piers (no dpc of course). In its favour, they did ensure cross ventilation with a crude grate at the front wall, and another on the cellar steps to the opposite wall. Plus the joists don't bear into to any exterior walls - just rest on the crude piers.

I doubt that the floor would be in such good condition if the timber was resting directly on the damp earth, and without ventilation.

My plan would be to repair any joists that have become rotten and weakened, replace the timber props with something more durable and get the ventilation sorted.

Easier said than done, but hopefully you will be able to save most of the structure.

 

[Ian Bond]

Someone previously has propped up the joists(2 years+ ago I think) and just stood un treated software in damp earth.....

Just noticed the software typo!

Not an IT nerd like me by any chance?

 

[markwm]

There are two air bircks under the living room, that's where the white fluffy stuff is. They are only a few feet away from the timber I'm worried about.

There are no air bricks under the hall(no white fluff either) but there is a hole between the hall and living room hence the reason I could see under the living room.

It feels quite drafty down there too, bricks are suprisingly good condition considering they are nearly 200 years old.

Some of the joist ends felt ok, others were soft-ish. Don't think I could stick a screwdriver all the way through though.

Guilty regarding the IT typo.

 

[Ian Bond]

OK Mark, so you just need to be satisfied that the affected joists are strong enough, and it's not just the floorboards holding them up!

With any luck it is just superficial, but you'll to have another look and let us know.

There are some good books on the subject of repairs, which may be of use. If only to check that you are getting reasonable advice from any builders you get in...

Here's a good 'antique' book that I've used in the past!
http://www.amazon.co.uk/House-Restorers-Guide-Hugh-Lander/dp/0715300032

I should point out that whilst Mr Lander is very good, he has an unfortunate habit of recommending the use of cement (albeit a weak mix) in his lime mortar recipes. That's the only thing I'd dare criticize him for though, others may disagree.

 

[Matt Green]

I'm more worried about the white stuff I can see under the living room. Not sure if it's some kind of mould or spiders webs/nests???

No. It's dry rot mycelium.

You need to clear all the timber junk off the earth, rake the floor and get an air blower down there. I take it that access might be an issue.

More later. I have to take the dog for a walk and I have a savage hangover.


Matt Green

 

[markwm]

I've now been under the living room. White stuff everywhere.......Also, a very dangerous prop that's rotted at the bottom and has started to bend. Looks like I have got lots of work to do :-/

check it out....

 

[Matt Green]

This photo show old dry rot damage in one of the joist ends. Given that dry rot spreads down through houses following the path of water percolation through the building fabric, this looks like a old problem back to haunt you. The damage on the joists looks old and fungus has started to attack the untreated timber in ground contact now that the masonry around the joist bearings has dried.

Nothing too much to worry about, but you do need to resupport the floor in this area. Removing those props and resupporting the floor should be the end point and I'd be inclined to put a hatch in the floor to periodically check the void beneath. Remove the decayed timber and isolate any repair pieces from the masonry with DPM or slate. Dry rot can be a bit of a pain get rid of in sub-floor voids if its growing across the earth, hence the need to rake the floor to get rid of all the timber fragments.

What does the earth look like under the floor? Dry and powdery or is it a bit of a river bed?

Hope that helps a bit, you should be able to deal with it. Are you aware of any previous outbreaks? Whomsoever dealt with it didn't do a spectacularly forward-thinking job of it.


Matt

 

[markwm]

This photo show old dry rot damage in one of the joist ends. Given that dry rot spreads down through houses following the path of water percolation through the building fabric, this looks like a old problem back to haunt you. The damage on the joists looks old and fungus has started to attack the untreated timber in ground contact now that the masonry around the joist bearings has dried.

Nothing too much to worry about, but you do need to resupport the floor in this area. Removing those props and resupporting the floor should be the end point and I'd be inclined to put a hatch in the floor to periodically check the void beneath. Remove the decayed timber and isolate any repair pieces from the masonry with DPM or slate. Dry rot can be a bit of a pain get rid of in sub-floor voids if its growing across the earth, hence the need to rake the floor to get rid of all the timber fragments.

What does the earth look like under the floor? Dry and powdery or is it a bit of a river bed?

Hope that helps a bit, you should be able to deal with it. Are you aware of any previous outbreaks? Whomsoever dealt with it didn't do a spectacularly forward-thinking job of it.


Matt

Where the old joists have rotted, do I need to cut off and remove these bad areas of timber? ie, remove ALL of the rotted timber from the cavity

I'm not aware of previous problems but I know when my sister moved in 2.5 years ago they had central heating installed and some work was done under the floor cavity. I recall myself looking down into the cavity while they were repairing some joists. This was before I had any kind of "diy" knowledge but I'm 100% sure that if I had seen all the mycelium I would have asked what I was, therefore it wasn't there 2.5 years ago. I'm sure the rotted timber was, hence the reason they propped it up.

So the plan is to go into the cavity, remove all the loose timber workman have left down there, scoop up and remove all the mould, use a fungicide too?..

When I come to repair the joists. Is it best to continue propping up? If so should I use timber or steel props? Or do I go with brackets like these? http://www.joist-repair.co.uk/

 

[Matt Green]

Where the old joists have rotted, do I need to cut off and remove these bad areas of timber? ie, remove ALL of the rotted timber from the cavity

If they are decayed to the point that they are no longer structurally capable of doing their job, yes. If it's just surface damage, there is no to remove timber as long as it remains fit for purpose.

I'm not aware of previous problems but I know when my sister moved in 2.5 years ago they had central heating installed and some work was done under the floor cavity. I recall myself looking down into the cavity while they were repairing some joists. This was before I had any kind of "diy" knowledge but I'm 100% sure that if I had seen all the mycelium I would have asked what I was, therefore it wasn't there 2.5 years ago. I'm sure the rotted timber was, hence the reason they propped it up.

In the interim 2.5 years, water has fallen through the wall and into the earth at the base. The untreated props were installed just in time for the fungus to attack it.

So the plan is to go into the cavity, remove all the loose timber workman have left down there, scoop up and remove all the mould, use a fungicide too?..

All sounds good except for the last bit. I wouldn't reach straight for the fungicide just yet. Clear it all out, rake the little timber bits from the floor and dry the earth with a fan. Put a hatch in and check it periodically. If you see any renewed growth on the earth sparingly apply something boron-based to it. It depends how much water and timber is in the soil, hence it can be a little problematic.

When I come to repair the joists. Is it best to continue propping up? If so should I use timber or steel props? Or do I go with brackets like these? http://www.joist-repair.co.uk/

I'd specify brackets or an isolated plate beneath rather than propping. Try to keep timber out of contact with the earth.


Matt

 

[Matt Green]

:shock:

http://groups.google.co.uk/group/uk...883c8/99d5bc3a68191ace?hl=en#99d5bc3a68191ace

 

[markwm]

:shock:

http://groups.google.co.uk/group/uk...883c8/99d5bc3a68191ace?hl=en#99d5bc3a68191ace

??

I posted the same pics there as here. Seems sensible to get as many opinions as possible.

 

[markwm]

Where the old joists have rotted, do I need to cut off and remove these bad areas of timber? ie, remove ALL of the rotted timber from the cavity

If they are decayed to the point that they are no longer structurally capable of doing their job, yes. If it's just surface damage, there is no to remove timber as long as it remains fit for purpose.

I'm not aware of previous problems but I know when my sister moved in 2.5 years ago they had central heating installed and some work was done under the floor cavity. I recall myself looking down into the cavity while they were repairing some joists. This was before I had any kind of "diy" knowledge but I'm 100% sure that if I had seen all the mycelium I would have asked what I was, therefore it wasn't there 2.5 years ago. I'm sure the rotted timber was, hence the reason they propped it up.

In the interim 2.5 years, water has fallen through the wall and into the earth at the base. The untreated props were installed just in time for the fungus to attack it.

So the plan is to go into the cavity, remove all the loose timber workman have left down there, scoop up and remove all the mould, use a fungicide too?..

All sounds good except for the last bit. I wouldn't reach straight for the fungicide just yet. Clear it all out, rake the little timber bits from the floor and dry the earth with a fan. Put a hatch in and check it periodically. If you see any renewed growth on the earth sparingly apply something boron-based to it. It depends how much water and timber is in the soil, hence it can be a little problematic.

When I come to repair the joists. Is it best to continue propping up? If so should I use timber or steel props? Or do I go with brackets like these? http://www.joist-repair.co.uk/

I'd specify brackets or an isolated plate beneath rather than propping. Try to keep timber out of contact with the earth.


Matt

The original joists ends aren't doing any good. They're not even resting on the masonry. I find it hard to tell if the damage warrants repair or not, is there some kind of rule? Some of the joists in the hall don't seem that bad to me but they're not that good either.

Someone mentioned covering the soild with weighted polythene, good idea or not do you think?

 

[Nemesis]

Disappointed Matt thought it something as prosaic as dry rot, I thought he might, but ectoplasm would have been so much more interesting.

However - I'd really recommend that you don't panic as suggested on that other place, :shock: and do as Matt has stated.

He does this for a living. Not spiritualism - wood stuff. Knows what he's talking about.

 

[markwm]

Seems so..

Very grateful for the advice

 

[Ian Bond]

Some of the advice in 'the other place' seems to be an over-reaction, along side some sound advice already offered here.

I'd go along with Dr Matt - seems to be the most economically and conservationally sound option to me!!!!

As long as you don't repeat the previous bodge, you should be OK.

The metal repair brackets you linked to look ideal for replacing any rotten joist ends, if there are any that are actually seriously weakened. Fortunately it's going to be hidden and doesn't need to be a cosmetic job, as long as it's structurally sound.

And the hatch is an excellent idea, and would be easy to do. It would certainly help you to keep and eye on things, and provide handing access for running cables and pipes.

 

[Nemesis]

He's here somewhere:

http://www.ridoutassociates.co.uk/personnel.htm


Excellent firm, if you do feel you can't DIY then highly recommended.

 

[Matt Green]

The original joists ends aren't doing any good. They're not even resting on the masonry. I find it hard to tell if the damage warrants repair or not, is there some kind of rule? Some of the joists in the hall don't seem that bad to me but they're not that good either.

Someone mentioned covering the soild with weighted polythene, good idea or not do you think?

Oh, no offence meant: yes definitely best to check in more than one place, its just that some of the advise on uk.diy would do more damage than the dry rot.

I'm not a structural engineer, I can't and don't make structural judgements. As a rule of thumb if theres 2/3rds of it left it will probably be ok, but do check regularly for cracking. If the bearings are not supported, then they probably should be.

Don't put polyethene down: if water can't evaporate through the earth, it will rise into the walls and evaporate from the surfaces into the voids intstead. Which would put water closer to the timber, which the opposite of what you want.

Cheers,

Matt.

 

[markwm]

I'd specify brackets or an isolated plate beneath rather than propping. Try to keep timber out of contact with the earth.


Matt

After reading the blurb about those brackets, it seems they are design to sit themselves in the joist support wall. I assumed they were design to join a new timber to the good part of the old timber.

The rot on my joists extends about 2 foot inwards, which is more than the 17 inch max cut off that these brackets can support.