repair wall plate?

[GerryC]

Hi all, i want to remove and replace a piece of the wall plate at the front of my timber-framed cottage. I can't find any web pages or books covering this specific task (loads about sole plates) though it must have been done millions of times. The complications are -
1. how do you best support the roof rafters that rest on the piece of wall plate you want to remove?
2. how do you work on the wall plate with the thatch right in your face?
3. And, in this particular case, how do you support the dormer window above the piece you want to replace while still leaving room to get the new piece in?

If anyone an advise how any of these are best done or point me in the direction of some instructions I would be most grateful - tin of home made biscuits?

 

[a twig]

1) Prop rafter by cutting a timber and fixing it between rafter and joist, usually where the purlins are - that will take the rafter’s load down onto the joist and allow you to cut back to good timber and hack out the old rotten stuff wall plate

2) not a thatch expert so will defer to others on here but potentially might have to remove some thatch and get it repaired later, or try and access from inside

3) I’d suggest window out and then prop the frame either internally with timber or externally off the scaffold (it’s not an “off a ladder” job so you’ll need scaffold anyway)

Keep the biscuits, you’ll need ‘em

 

[GerryC]

1) Prop rafter by cutting a timber and fixing it between rafter and joist, usually where the purlins are - that will take the rafter’s load down onto the joist and allow you to cut back to good timber and hack out the old rotten stuff wall plate

Hi Twig and thanks very much .. can i make sure i understand ... is the bit in red in the picture what you mean? (Its an H frame by the way) ...if so, I guess I should also prop underneath the 1st floor joists immediately underneath as the joists are slight and over 12 ft with no support apart from each of the two walls?

 

[Cubist]

Before going any further I am a little concerned to make sure that we have a thorough understanding of the challenge and that we are all on the same page concerning the terminologies involved. With this in mind: -

1. Is it safe to assume that the wall plate you refer to is immediately below the upper floor window frame in your picture?
2. Is this a full beam spanning a pair of the bents of the house and upon which the bird-mouth of the rafters are mounted?
3. What is the nature and extent of the damage/decay to the beam and has the extent been verified?
4. How much, what length, of the wall plate must be replaced?
5. What are the dimensions (L/B/D) of the wall plate beam?
6. Is the length of the replacement timber less than the complete width of the bedroom(?} pictured?
7. Is it possible to manoeuvre the new section of beam into the room(s) on the upper floor?

Sorry for all the questions, I may have others, but I would be seeking to effect the repairs without interfering with the thatch if at all possible as any work to remove, even limited sections, and make it good later could be very expensive and, perhaps more importantly, it may take months to find a competent thatcher to do the work.

 

[GerryC]

Hi Cubist, good questions and id like to avoid the thatch too

1. Is it safe to assume that the wall plate you refer to is immediately below the upper floor window frame in your picture? YES
2. Is this a full beam spanning a pair of the bents of the house and upon which the bird-mouth of the rafters are mounted? YES .. the beam goes acriis neighbours house too
3. What is the nature and extent of the damage/decay to the beam and has the extent been verified? About 6ft immediatly under window is decayed - water wear, stuctural engineer inspected says needs replacing.
4. How much, what length, of the wall plate must be replaced? 6 ft
5. What are the dimensions (L/B/D) of the wall plate beam? 5 x 6 inch beam, 14ft across on my part and a further 6ft neighbours
6. Is the length of the replacement timber less than the complete width of the bedroom(?} pictured? yes its a little wider than the width of the window
7. Is it possible to manoeuvre the new section of beam into the room(s) on the upper floor? yes

 

[Cubist]

Hi Gerry,
Ok, so some further questions and maybe some thoughts on how to proceed.

The challenges are then;

1. How to support the roof and the bay window while providing enough space to remove and replace the beam section.
2. Where and how to cut the extant beam cleanly to allow the new section of timber to be scarfed into place without damaging or displacing the rafters mounted to the bad section AND without interfering with or damaging the thatch.
3. Also, how to make sure that the joint between the old and new timber is structurally sound and does not compromise the integrity of your AND the neighbours bents. [BTW - is your neighbours section of the beam in good order?]
4. How to re-fix the rafters to the new beam section without removing/displacing the thatch. [Is there a fire barrier installed below the thatch?]

Theres a lot here that needs to be thought through and it's best to determine the needed solutions in reverse order before making any final decisions or taking any action. I suspect we may be having several conversations in the coming days - some of these are multi-teapot questions.
Speak soon,
Cubist

 

[GerryC]

Cheers,
re yr 3. the structual engineer has recommended a butt joinst only and connecting the new oiec with the existing via a steel plate front and back. The steel plate would go across and at least 50cm wider each side of the replacement piece and be bolted through. Reasoning i believe is that the position is in the middle and the thrust of roof spread is greatest at mid point between the gable and party walls therefore not a good place for a scarf joint on a piece of wall plate without additional support v. outward thrust.

re yr 4. no fire barrier i,m aware of though i have not stared to strip the wall panels yet.

Thank God for tea and biscuits!

 

[Cubist]

Cheers,
re yr 3. the structual engineer has recommended a butt joinst only and connecting the new oiec with the existing via a steel plate front and back. The steel plate would go across and at least 50cm wider each side of the replacement piece and be bolted through. Reasoning i believe is that the position is in the middle and the thrust of roof spread is greatest at mid point between the gable and party walls therefore not a good place for a scarf joint on a piece of wall plate without additional support v. outward thrust.

re yr 4. no fire barrier i,m aware of though i have not stared to strip the wall panels yet.

Thank God for tea and biscuits!

That makes sense even though I have no idea what 'oiec' is.

When we bought this place, I was wise enough to also invest in a tea plantation and a few shares in McVities.

 

[GerryC]

oiec ! drinking too quickly! ... connecting the new one with the existing one ... that is, connecting the new pice of wall plate with the existing parts via two steel plates on the face and back bolted through ...
ATB

 

[a twig]

Hi Twig and thanks very much .. can i make sure i understand ... is the bit in red in the picture what you mean? (Its an H frame by the way) ...if so, I guess I should also prop underneath the 1st floor joists immediately underneath as the joists are slight and over 12 ft with no support apart from each of the two walls?View attachment 10328

Yep, that was the rough idea - yep an acro underneath would be a good idea.

I see Cubist is on the case so will leave you guys too it

 

[stuart45]

Did your SE have any thoughts on how to tackle the job?

 

[GerryC]

Hi Stuart, the SE's position is that the contractor should know how to do all this ... but i cant find a contractor who will take it one or have a sensible converstaion about why they cant help me with it ... i suspect i'm going to have to do it myself in which case i will certainly be going back to the SE but don't know how much gap there will be between the engineering/physics view of it and the hands on part so he may not have all the answers ... the trade spends most of its time on non-period bricks and mortar I guess ...

 

[Cubist]

Good morning Gerry,
I've been pondering how the necessary work can be done and think I have a plan that would work. Mostly it's fairly straightforward and there are few technical elements that pose significant challenges for someone with reasonable woodworking skills, access to suitable tools and someone to help with the heavy lifting. If you are comfortable you have, or can acquire, those resources, we can discuss the plan in greater detail and throw it open to others here for wider discussion and assessment.
Cheers,
Cubist (aka Steve)

 

[Cubist]

Yep, that was the rough idea - yep an acro underneath would be a good idea.

I see Cubist is on the case so will leave you guys too it

Why thank you Twig. Always grateful for such kind acknowledgments but nevertheless worried that such confidence may be misplaced/misguided.

 

[GerryC]

Good morning Gerry,
I've been pondering how the necessary work can be done and think I have a plan that would work. Mostly it's fairly straightforward and there are few technical elements that pose significant challenges for someone with reasonable woodworking skills, access to suitable tools and someone to help with the heavy lifting. If you are comfortable you have, or can acquire, those resources, we can discuss the plan in greater detail and throw it open to others here for wider discussion and assessment.
Cheers,
Cubist (aka Steve)

Hey Steve, yes I expected to need and have all those resources one way or another and would be every pleased to get good direction from someone who knows ... do please advise

 

[Cubist]

Hey Gerry,
Step one, as always, is a little more investigation work. You will need to know how the frame of the dormer bay is fitted and whether additional support will be required to hold it in place while all the key work is done. The key concern here is that you do not want the dormer to sag or otherwise move as this could cause damage to the roof components above and the thatch. I'm assuming that the beam is oak but it could be a different species. I ask because the timber, depending on its age, can be incredibly hard to work even with power tools. A reciprocating saw with wood cutting blades no less than 10 inches in length will be needed as will a couple of good 30mm-50mm wood chisels. A multitool with hardwood and metal saw blades will also be useful.

And here's the health warning - heat build up in power tool blades while cutting old and hard timbers is a major fire risk and extreme caution is needed if they are used near thatch. Water based extinguishers must always be on hand and a water spray mister of the garden type should also be available to wet down any cuts if the room is to be left unattended.

Back to the investigation work. Concerning the old beam; you need to check the location of any large knots in the wood as these may influence the length of the segment that needs to be cut out and therefore the length of the new timber. Oak is nicknamed 'Ironwood' for a very good reason and the knots in old oak can be as strong as hardened steel and cause major problems for even a chainsaw! Once you have a clear idea of the final length that needs to be cut out of the old beam, and depending on when you may hope to do all this work (I would be aiming for summer), you can think about buying the timber you will insert. It would be wise to add say 10% to the overall length to allow for the unfortunate positions of any knots, ideally you want none within 12 inches of each end of the new beam. When buying the beam be careful to ensure that its a seasoned timber and not green wood - green oak is wonderful to work with but, as it seasons, it can twist, bend/warp and shakes (splits) can arise. Also, despite having been seasoned properly at the lumber yard the timber will continue to shrink for some considerable time - oak is a timber that needs to acclimate on site and ideally in the building in which it is to be used for a month or two at the very least for the dimensions needed.

Another health warning - Do not be tempted cut the new beam to length or cut the lap joints, until the old one is taken out as you may find some alteration is vital.

There will be some problems with the fastenings used to fix the 'birds-mouths' of the rafters where these rest on the old beam, First is that these fastenings will need to be cut before the old beam is removed - this is to avoid the prospect of the beam dangling in space held by just a few old nails or pegs and perhaps also causing the rafters to move and suffer damage. We can discuss how to do this later but for now you only need to consider the bracketry that will be needed to fix the foot of each rafter to the new beam as these will need to be fitted to the new beam before it is finally installed. There are many potentially suitable brackets on the market but it will be important that the selected brackets can be firmly screwed into place on the beam 'and' the side of the rafter without compromising the slope of the roof.

Last health warning, for now; this job is not something that can be done in a weekend. Be ready for a long and, at times dirty and sometimes risky, exercise that offers more than just a few personal challenges. Hopefully though good planning now will reduce the overall time needed to finish the job effectively. Given the size of the house you may need to give serious consideration to sleeping arrangements.

Nuff for now, more later when you have some feedback re the above.

Cheers,
Steve

 

[GerryC]

Hey Gerry,
Step one, as always, is a little more investigation work. You will need to know how the frame of the dormer bay is fitted and whether additional support will be required to hold it in place while all the key work is done. The key concern here is that you do not want the dormer to sag or otherwise move as this could cause damage to the roof components above and the thatch. I'm assuming that the beam is oak but it could be a different species. I ask because the timber, depending on its age, can be incredibly hard to work even with power tools. A reciprocating saw with wood cutting blades no less than 10 inches in length will be needed as will a couple of good 30mm-50mm wood chisels. A multitool with hardwood and metal saw blades will also be useful.

And here's the health warning - heat build up in power tool blades while cutting old and hard timbers is a major fire risk and extreme caution is needed if they are used near thatch. Water based extinguishers must always be on hand and a water spray mister of the garden type should also be available to wet down any cuts if the room is to be left unattended.

Back to the investigation work. Concerning the old beam; you need to check the location of any large knots in the wood as these may influence the length of the segment that needs to be cut out and therefore the length of the new timber. Oak is nicknamed 'Ironwood' for a very good reason and the knots in old oak can be as strong as hardened steel and cause major problems for even a chainsaw! Once you have a clear idea of the final length that needs to be cut out of the old beam, and depending on when you may hope to do all this work (I would be aiming for summer), you can think about buying the timber you will insert. It would be wise to add say 10% to the overall length to allow for the unfortunate positions of any knots, ideally you want none within 12 inches of each end of the new beam. When buying the beam be careful to ensure that its a seasoned timber and not green wood - green oak is wonderful to work with but, as it seasons, it can twist, bend/warp and shakes (splits) can arise. Also, despite having been seasoned properly at the lumber yard the timber will continue to shrink for some considerable time - oak is a timber that needs to acclimate on site and ideally in the building in which it is to be used for a month or two at the very least for the dimensions needed.

Another health warning - Do not be tempted cut the new beam to length or cut the lap joints, until the old one is taken out as you may find some alteration is vital.

There will be some problems with the fastenings used to fix the 'birds-mouths' of the rafters where these rest on the old beam, First is that these fastenings will need to be cut before the old beam is removed - this is to avoid the prospect of the beam dangling in space held by just a few old nails or pegs and perhaps also causing the rafters to move and suffer damage. We can discuss how to do this later but for now you only need to consider the bracketry that will be needed to fix the foot of each rafter to the new beam as these will need to be fitted to the new beam before it is finally installed. There are many potentially suitable brackets on the market but it will be important that the selected brackets can be firmly screwed into place on the beam 'and' the side of the rafter without compromising the slope of the roof.

Last health warning, for now; this job is not something that can be done in a weekend. Be ready for a long and, at times dirty and sometimes risky, exercise that offers more than just a few personal challenges. Hopefully though good planning now will reduce the overall time needed to finish the job effectively. Given the size of the house you may need to give serious consideration to sleeping arrangements.

Nuff for now, more later when you have some feedback re the above.

Cheers,
Steve

Hey Steve, great stuff, Thanks ..

re fire risk: when using such hot tools i could water down the thatch before a session as additional precaution?

re "how the frame of the dormer bay is fitted and whether additional support will be required to hold it in place while all the key work is done". The front posts of the dormer are flush with the front of the wall plate. It looks like the two front posts of the dormer come down onto the wall plate at the same place as the rafters (horizontal view) over which the dormer is built . That would be as expected no? At some point I could take away materials, cladding etc to be sure ... but is there any alterative other than that the front posts and rafters touch the wall plate right next to each other - i.e. into the same tennon or the post nailed/bolted to the rafter? I cant see yet how the rafter are connected to the wall plate - birds mouth or other - but i can see that one of the rafters is being pulled by the roof spread. I

Re knots: thanks wouldn't have through of this - will inspect although i am not going to be be able to see the top plane of the wall pate of course unless I remove thatch - should i do that or just inspect from the inside and outside view of the plate and when ive taken away the infills, the underside?

RE brackets: !ah, there was me thinking that birds mouth would use the weight of rafter and thatch to stay in place and 17th century guys didn't use matal straps! I guess the best thing will be to get a view of what's been used here ... I'm just about to start taking plaster off internal side of wall so I can see the timber structure before putting straps and needles through ... so i'll see if i can get a detailed view of one of the rafters joining the plate and let you know and if poss photo

ATB, Gerry


...

 

[Cubist]

Hi Gerry,

1. Considering that the underside of the thatch will, if it's doing its job properly, be bone/tinder dry, tt would be a good idea to wet it down before making any cuts but nevertheless its best to keep any hot metals/blades away from it.
2. Dormer - I suspected as much and it poses a challenge insofar that the window frame and their posts will need to be supported somehow while the work is done. Whatever is used to provide that support must not block or hinder access to remove the old beam and install the new one. Some photographs would be helpful to consider alternatives. Also, the base of the dormer window frame is almost certainly fastened into the wall plate somehow. These fastenings are most likely to be nails or screws and you should be able to locate them beforehand by examining the upper face of the window sill. At his stage I'm guessing that the weight of the dormer is carried by the wall plate and the posts are connected in a right angle pattern to the neighbouring rafters. It's unlikely that any connections into the wall plate would be morticed and tenoned so you can expect nails and screws. Traditionally wooden pegs would have been used to secure the birds mouth of the rafters in place but iron/steel nails made that approach redundant when they became commonly available.
3. Knots - that's why I urged you not to cut the new beam until after the old one has been removed. Some surpises always hide and are only revealed at the last minute.
4. Brackets - metal (iron/steel) have been available for a long time so don't be surprised if you find them. Unlikely though as nails are/were a much cheaper option.

This may be a dumb question but... have you considered just how you would get a 2 metre beam weighing close to 100kg into that room? Could be a gotcha.

 

[GerryC]

Hi Gerry,

1. Considering that the underside of the thatch will, if it's doing its job properly, be bone/tinder dry, tt would be a good idea to wet it down before making any cuts but nevertheless its best to keep any hot metals/blades away from it.
2. Dormer - I suspected as much and it poses a challenge insofar that the window frame and their posts will need to be supported somehow while the work is done. Whatever is used to provide that support must not block or hinder access to remove the old beam and install the new one. Some photographs would be helpful to consider alternatives. Also, the base of the dormer window frame is almost certainly fastened into the wall plate somehow. These fastenings are most likely to be nails or screws and you should be able to locate them beforehand by examining the upper face of the window sill. At his stage I'm guessing that the weight of the dormer is carried by the wall plate and the posts are connected in a right angle pattern to the neighbouring rafters. It's unlikely that any connections into the wall plate would be morticed and tenoned so you can expect nails and screws. Traditionally wooden pegs would have been used to secure the birds mouth of the rafters in place but iron/steel nails made that approach redundant when they became commonly available.
3. Knots - that's why I urged you not to cut the new beam until after the old one has been removed. Some surpises always hide and are only revealed at the last minute.
4. Brackets - metal (iron/steel) have been available for a long time so don't be surprised if you find them. Unlikely though as nails are/were a much cheaper option.

This may be a dumb question but... have you considered just how you would get a 2 metre beam weighing close to 100kg into that room? Could be a gotcha.

Hey, re 2 metre beam weighing close to 100kg ah, i have handled 5" x 5" oak (green) and figured two guys could easily manoeuvre a 6ft length of 4"x5" - i thought it would weight in region of 50 lbs - so thata about 22kb? 100kg ! yikes. But if that can sit on wall plate, it can sit on the support props ive put in place to support the floor: at every 16 inches (under each joist) Ive put a 2'' x 8" post into a 2x8 across the ceiling, about a foot inside the front wall. Because the stairwell is open I can get the new oak piece onto the floor above those supports ... without having to lift up all of the stairs as such. But could 3 guys lift 100kg - that's 70 bags of sugar each, i don't think so ... that weight would imply machinery to lift it into position even on the outside no? Am I misunderstanding?

 

[GerryC]

sorry "easily manoeuvre a 6ft length of 4"x5" " >>>should be >>> easily manoeuvre a 6ft length of 5"x6"