Very Spingy floor

[danjennings1958]

We have a 15th century house over 3 floors, the upper floors being added in the 18th & 19th century.

The top floor has one room with a very springy floor. It has very old wide oak planks that will be difficult to remove.

We believe that the beams below aren’t too long, they are just too thin or of a poor cut to allow strength, being full of knots and cracks across the width of the timbers. There’s a bow in the length of some of the timbers and some of the ends have separated from the main supporting cross beams

There is space to strengthen from above by adding timbers above the floors boards and screwing through to the beams below, laying a new flow over. But this does not feel right.

I dont want to have to remove the suspect beams and replace with something more substantial as it’s a huge job and very disruptive.

Any other suggestion’s for me please?

 

[Toby Newell]

We have a 15th century house over 3 floors, the upper floors being added in the 18th & 19th century.

The top floor has one room with a very springy floor. It has very old wide oak planks that will be difficult to remove.

Photos please of the top floor and the beams underneath. Very wide oak boards could be period earlier than C18th.

We believe that the beams below aren’t too long, they are just too thin or of a poor cut to allow strength, being full of knots and cracks across the width of the timbers. There’s a bow in the length of some of the timbers and some of the ends have separated from the main supporting cross beams

Why do you believe timbers that have held up a floor for up to 300 years are too thin?

Why do you believe these are a poor cut? They most likely would have been green oak from the centre of a limb / trunk, there is no possibility of 'poor cut' unless a trunk was partially air dried, then split down the middle and tension was released.

Full of knots? Please send photos.

Cracks accross the width of the timbers? Accross the width??? wood does not crack accross it's width, it simply breaks, if this is the case you need to replace them.

Bows in a C15th house are perfectly normal.

Beams? Cross beams? You mean joist and Summer beams. I am curious as to how you do not know the name of your timbers yet have deduced that the carpenter did not cut them correctly.

If the joist have shrunk away from the beams they will need to be replaced or packed and refixed. This can be helped by fitting noggins although obviously not an option if your joist are exposed from below.

There is space to strengthen from above by adding timbers above the floors boards and screwing through to the beams below, laying a new flow over. But this does not feel right.

Correct. This is not right. You would simply be adding dead weight to an unstable structure if, as you say, your joist have cracks accross their width and are loose in their mortices. Thus this is actually counter productive.

I dont want to have to remove the suspect beams and replace with something more substantial as it’s a huge job and very disruptive.

Any other suggestion’s for me please?

If your joists are exposed below (as it sounds like they are as you can obvioulsy see them) then you will need to remove the floor and replace.

If your joists are underneath plaster then you can maybe save some joists by sistering and with noggins, I do this all the time.

It sounds like you have lots of ideas but little knowledge. Hopefully things are not as bad as you presume, in that case you might be able to save the joist.

If things are as bad as you say, weak, twisted, loose joist that is broken accross it's width then they will need replacing.

Either way the floor has to come up.

If the joist are not exposed from below you may be able to save the ceiling. If they are exposed you will have to drop the ceiling too.

Any other suggestions? I guess the horse has already bolted on the don't buy a house built in the 1400s then. Incredibly frustrating but incredibly beautiful.

Start looking for lime plasterers if you need one and a good timber framer, never use a general builder, unless they are actually really timber framers that also do general building work. Look early and be prepared to wait.

What part of the country are you in?

 

[Toby Newell]

To elaborate. Theoretically (although quite a lot for your CO to accept if he ever needs to visit) you could strengthen from above at least by overjoisting the central Bressummer. However often the side beams / top plates are at the very edge so getting a fix would be difficult. Essentially the wall ends would be unsupported.

Also if your joist aren't in great condition you couldn't rely on construction screws. You would need through bolts and large square washers.

BC would require 16mm coach bolts through the main beams at least.

Good luck drilling straight through a 300 year old oak Bressummer with a 16mm 18in long auger bit.

 

[Toby Newell]

sometimes (most of the jobs I take on) the ceiling and timbers can be saved... (apart from any part I put my foot through)


if exposed the ceiling is sadly bye bye...



but please send photos, it's perfectly possible your joist are not as bad as you think. And yes, here in the last photo the side beams are partially inbound as this is a middle room, so theoretically your overjoisting idea is in theory at least, possible. Whereas if any of the walls are exterior, then probably not.

 

[88v8]

Photos please of the top floor and the beams underneath. Very wide oak boards could be period earlier than C18th.

Why do you believe timbers that have held up a floor for up to 300 years are too thin? If your joists are exposed below (as it sounds like they are as you can obviously see them) then you will need to remove the floor and replace.

Our attic beams (elm) are thin, but then they were never designed to support anything other than the ceiling.
I don't even walk up there, would crack the plaster, and I'm not heavy.

On the other hand a springy floor with no plaster beneath might be fine... depending what's going to be on there. Bath, double bed, hmmm.

Toby, you may be right, but as you know all too well it's very hard even for a pro to pull up old oak boards due to the tannin/rusting nails, this is not something I would want to do as it could be quite damaging. Might be lucky, punch the nails in, probably not unless the floor has been unusually dry. At best, one is likely to destroy one edge board and even with care and a wide bolster I would not be sure of avoiding more damage. And then of course there's the skirtings if any.

How would you go about taking up an old oak floor?

Ivor

PS yes, pics. Use Photobucket or the like.

 

[Toby Newell]

Punch the nails in?
Ok. No.
Japanese cats paws, superbars, no bolsters.

Bolsters would snap boards, punching nails in C18 C19 oak? very unlikely. Even if you dont have 10mm roseheads like my last job, any forged or even cut nail is not going to punch. It's going to crumble the head or just plain not move. If it does move forcing the large head through the board is going to damage everything because of the hole created plus all the impact (vibration) damage. You remove with cats paws and pincers or break off the head to aid lifting. This will damage the top area around the head but much less destructive and much more physically possible.

(Note: Beams = main supports = llel to boards. You mean joists = board supports = right angle to boards)

The OP said the joists were weak and broken (cracked accross) without lifting floor you cannot support at wall, so impossible to fix from above without removing boards.

It's possible it's all fine and looks worse than it is and can be left, but if it is as bad as described then it may require attention and there is nothing you can do without lifting boards.

 

[danjennings1958]

Ive been working on some other things so no recent replies - i can see lots of suggestions but just to make one thing clear - im not a builder a good DIYer at most and probably wont be attempting this myself. My description of various beams, whatever you might want to call them might not be correct, but as i said I'm not a builder. I'm trying to understand what might be involved so that i dont get mugged by a rip off builder selling me his dark art skills. Im also trying to not remove the old oak flooring above the suspect beam, but if i have to , what might be the best way, as a start at least? I can then see what Im faced with for the next stage.
Ive added a few pictures of the suspect beams and the cracks in them and the floor which may well be older than i suggested but im only working on the history of the house as i know it which suggests it was originally build at the lower level around 1470 and added to over the years, the latest being a few hundred years ago. If anyone has any useful suggestions, it would be appreciated.
Thanks

 

[Cubist]

Hello Dan,

Being responsible for all the bills associated with the upkeep and maintenance of a timber frame house dating back to 1550-70 I can thoroughly empathise as I'm sure other members here do. Unlike yourself though I have the advantage of an engineering background and an unwillingness to pay others to make the same mistakes I am more than capable of. Whilst your posts concerning the state of the upper floor of your home are quite clear they do not provide any guidance concerning your objectives other than to avoid getting ripped off.

Could you help me/us please to get a better handle on what it is you want to achieve? What are your primary aims here? To conserve as is? To make safe for domestic use? To modernise and enhance?

There are some here who are happy to help and have relevant experience to share but we do need a little more guidance from you.

Cheers in anticipation.
Cubist

 

[CliffordPope]

What about lifting the board a fraction with a wedge enough to get a very fine hacksaw blade in to cut the nails? If you can get a thin bit of tinplate in as well that would protect the board from scratching.

 

[Cubist]

In the past I've used a very simple approach to check for deflection of joists, ceilings and the like. This uses two lengths of square or rectangular section wood. These are firmly held face to face and then slid apart so that the ends are in contact with both the floor and the underside of the joist. Strike a pencil line across both the aces of the wood and then get someone to stand/walk immediately above. Any deflection will be immediately obvious and the extent can be crudely measured..

 

[Kearn]

View attachment 14473

early wide joists… makes sense with your age guesstimate. Sadly, this one has failed. Shakes along the length are perfectly acceptable and have been there since the year after the house was built.

Stand under this while somebody walks above and you’ll see the movement. Be careful though…!

Not knowing the spacing, dimension etc and what is above, it’s impossible to say what to do. A structural engineer will calculate on their laptop and the result will be steel. They don’t like wood as it doesn’t behave uniformly and can’t be predicted.

There may be methods of appending this joist with metalwork, but it will be intrusive - likely mid to full length steel, routed into the top of the joist, making the cracked area purely visual she’s also don’t like scarfing joists/purlins due to the variegated forces exerted on them. Simplest option may be to replace it entirely.

All is very circumstantial though.

What you need is a good conservation structural oak framer to look, advise, fix. Now they are also hard to find…

 

[danjennings1958]

Hello Dan,

Being responsible for all the bills associated with the upkeep and maintenance of a timber frame house dating back to 1550-70 I can thoroughly empathise as I'm sure other members here do. Unlike yourself though I have the advantage of an engineering background and an unwillingness to pay others to make the same mistakes I am more than capable of. Whilst your posts concerning the state of the upper floor of your home are quite clear they do not provide any guidance concerning your objectives other than to avoid getting ripped off.

Could you help me/us please to get a better handle on what it is you want to achieve? What are your primary aims here? To conserve as is? To make safe for domestic use? To modernise and enhance?

There are some here who are happy to help and have relevant experience to share but we do need a little more guidance from you.

Cheers in anticipation.
Cubist

Thanks Cubist - The floor as it dosent feel safe to use, we really want to improve it so that we can add a bed. There is sufficient space to add a joist across to make it effectively float, without it touching the floor below it. Taking up the flooring boards as they are isnt really an option as im sure well end up replacing everything so building something over the top is favourite. I like you idea of using two lengths of square or rectangular section wood and testing, so i think ill give that a try and get back to you.
I appreciate the feedback, cheers.

 

[danjennings1958]

early wide joists… makes sense with your age guesstimate. Sadly, this one has failed. Shakes along the length are perfectly acceptable and have been there since the year after the house was built.

Stand under this while somebody walks above and you’ll see the movement. Be careful though…!

Not knowing the spacing, dimension etc and what is above, it’s impossible to say what to do. A structural engineer will calculate on their laptop and the result will be steel. They don’t like wood as it doesn’t behave uniformly and can’t be predicted.

There may be methods of appending this joist with metalwork, but it will be intrusive - likely mid to full length steel, routed into the top of the joist, making the cracked area purely visual she’s also don’t like scarfing joists/purlins due to the variegated forces exerted on them. Simplest option may be to replace it entirely.

All is very circumstantial though.

What you need is a good conservation structural oak framer to look, advise, fix. Now they are also hard to find…

Thanks - The pictures show just one joist, in all there are 3 of 4 with defects, some with 2-3 shakesa you call them. All old im sure and probably been there a while but the previous owners of the house ( for 40 years ) were the type to leave it and do nothing and im sure the room was unused for many years because of that . Below is our main bedroom and when someone walks above you cant actually see any movement. you can feel the flex above. Things standing on the floor will move as you walk across. we had thought about Steels, but id rather try and solve with timber if we can. I do know an oak framer who trained at a very well known local village famous for its oak framed properties ( Lavenham ) but he's very difficult to get hold of.

 

[Cubist]

Hi Dan,
If you find that there is no, or very limited, deflection of the joists using the slip-stick it becomes more likely that it is the floorboards themselves that are flexing. From your photos it appears that the ceiling below and between the joists is plastered and I see what appear to be wooden quadrant mouldings fixed to the face of the joists. This suggests that the ceiling plaster was not applied to the lower face of the floorboards and therefore, if there were significant movement of the joists the surface of the plaster would most likely show signs of cracking and loss of material.

If the above proves true then the job becomes much easier in some respects as there are several strategies you could employ to strengthen the at risk joists and remove the spring in the floor to make it capable of supporting foot traffic and furnishings loads. These can be discussed later when you have confirmed the situation.

Cheers,
Cubist

 

[danjennings1958]

Hi Dan,
If you find that there is no, or very limited, deflection of the joists using the slip-stick it becomes more likely that it is the floorboards themselves that are flexing. From your photos it appears that the ceiling below and between the joists is plastered and I see what appear to be wooden quadrant mouldings fixed to the face of the joists. This suggests that the ceiling plaster was not applied to the lower face of the floorboards and therefore, if there were significant movement of the joists the surface of the plaster would most likely show signs of cracking and loss of material.

If the above proves true then the job becomes much easier in some respects as there are several strategies you could employ to strengthen the at risk joists and remove the spring in the floor to make it capable of supporting foot traffic and furnishings loads. These can be discussed later when you have confirmed the situation.

Cheers,
Cubist

Hi Cubist.
The ceiling below isnt plastered, it board that is held in place by the quadrant. You might be right about the floors boards that are flexing and not the beams, i assume it was as they have cracks/defects in them. let me do what you suggest and get back to you.
Very much appreciate you help.
Cheers
Dan

 

[Cubist]

Noting your reply regarding the nature of the material used between the joists in the room(s) below I've taken another look at the photos you supplied. Typically flooring joists used in these old places are found to be roughly 100mm x 100mm (4x4 inches) or sometimes 100mm x 150mm (4x6inches), unlike any beams making up key elements of the buildings frame which will be much more massive. On the basis of that assumption, and your photo, it seems that a previous owner has cut pieces of some sheet material and pinned these directly to the floorboards above and applied a quadrant trim to close any gaps around the edges. I'm guessing therefore that the visible exposed depth of the joists below would be found to be in the order of 75mm - 125mm (3 - 5 inches).

An easy test to confirm that conclusion would be to use a small diameter wood drill to cut a hole near the middle of one of the ceiling panels. Done gently when the drill bit fully penetrates the sheet material there would be a brief moment when there is no resistance to pressure until the head of the drill bit contacts the floorboard material above. Once done, the hole can easily be filled and painted if desired or necessary.

I mention this as I think theres a good chance that should you need to take up the existing floor, as I think you may, there is a very good chance that what appears to be ceiling infill panels below will come out with the boards or simply fall out when you begin to lift them - they certainly should not be asked to carry any weight.

In terms of strategies to remove the spring or bounce in the floorboards there are only variations around just two themes. The first requires the removal of the floorboards to allow the insertion of strengthening splints for the joists and additional noggins between them to allow greater support for the final floor above. The second relies on the addition of a new material on top of the existing flooring to deliver much improved weight distribution for point loads. This approach however, whilst much easier in some respects, has other implications that may rule it out.

 

[danjennings1958]

Noting your reply regarding the nature of the material used between the joists in the room(s) below I've taken another look at the photos you supplied. Typically flooring joists used in these old places are found to be roughly 100mm x 100mm (4x4 inches) or sometimes 100mm x 150mm (4x6inches), unlike any beams making up key elements of the buildings frame which will be much more massive. On the basis of that assumption, and your photo, it seems that a previous owner has cut pieces of some sheet material and pinned these directly to the floorboards above and applied a quadrant trim to close any gaps around the edges. I'm guessing therefore that the visible exposed depth of the joists below would be found to be in the order of 75mm - 125mm (3 - 5 inches).

An easy test to confirm that conclusion would be to use a small diameter wood drill to cut a hole near the middle of one of the ceiling panels. Done gently when the drill bit fully penetrates the sheet material there would be a brief moment when there is no resistance to pressure until the head of the drill bit contacts the floorboard material above. Once done, the hole can easily be filled and painted if desired or necessary.

I mention this as I think theres a good chance that should you need to take up the existing floor, as I think you may, there is a very good chance that what appears to be ceiling infill panels below will come out with the boards or simply fall out when you begin to lift them - they certainly should not be asked to carry any weight.

In terms of strategies to remove the spring or bounce in the floorboards there are only variations around just two themes. The first requires the removal of the floorboards to allow the insertion of strengthening splints for the joists and additional noggins between them to allow greater support for the final floor above. The second relies on the addition of a new material on top of the existing flooring to deliver much improved weight distribution for point loads. This approach however, whilst much easier in some respects, has other implications that may rule it out.

Hi There.
Thanks for your observations, they helped me a lot.
Ive solved the issue by hanging new joists across from one main beam to th eother as i had sufficient head room to allow at least 100mm increase. so i laid 75mm joists and will strengthen them by sistering each beam to make them 150mm, this has taken out any spring in the new floor and more importantly raised the floor above the old springy floor so nothing ive added is in contact with the old floor. Ill be laying 12mm ply flooring over the top to complete.
Once the new joists were added you can see the amount the old floor has dropped in the centre by the gap between old and new.
so hopefully issues solved without taking up old flooring and replacing with new joists.

 

[Cubist]

I think you made the right strategy choice there, well done. Hopefully, depending on the use intended for the room you may consider finishing the floor with something a little more attractive than ply.

BTW a few years back I went through a very similar problem here to level and strengthen a bedroom floor that had up to 200mm of height variations.