90's Timber Frame House Advice

[Space Race]

Hi All,

 

Perhaps this isnt the right place given its historic rather than current but I’ll try my luck. I’m looking for any advice regarding buying an older timber framed house. Considerations, Risks, Positives etc. Coming from block wall builds it’s an area i know little about and most info seems to be for newer construction.

 

Were in the early stages of a house purchase in the North East of Scotland. The house was constructed in the 90’s and is a detached one off (i.e not a development) in a rural area. We assumed it was of block construction but have since found out this isnt the case. The outer leaf is 140mm concrete block with render whilst the inner is timber framed. I do not have any other details re the wall build up. Whilst timber frame construction is now very common I’m wary as to how good this might have been in the 90’s.

 

There are no visual signs of problems but no survey other than the home report has been done.

 

Thanks

[SteamyTea]

I have a 1987 TF place, no problems.

 

Just get a proper survey done.

[ProDave]

Timber frame has been common in Scotland for a very long time so I would have been surprised if it was not timber frame.

 

You can be pretty certain it was built with a 100mm timber frame.  the unknown for that era is what, if any insulation was fitted in the frame.  Earlier than 90's it would have been none, just a hollow frame.  It would be a simple matter of unscrewing a light switch or a socket and having a look to see, but not something a surveyor would do and you would need to ask the vendor if you can do that to look and see.

 

If there is no insulation then it is not a trivial job to upgrade it, pretty much all the plasterboard would have to come off to retro fit it, unless anyone knows if it is possible to install a blown in product, but even that would mean 2 holes in each section of wall so still not trivial.

 

If it were me, I would ask the vendor if I could take a look.

[Space Race]

2 minutes ago, SteamyTea said:

I have a 1987 TF place, no problems.

 

Just get a proper survey done.

Thanks, From the surveys I have seen done they really are very basic and I'm not sure how much we would benefit. Unless It's a wreck where the surveyor can get intrusive or there are obvious signs. Are there certain things to look out for with this type of construction?

[Space Race]

Thanks ProDave, I have read that cavity insulation can be a big problem with timber framed. You say within the frame so the cavity is maintained correct?

[twice round the block]

Re-done the bathroom on our 90's build one.

On the outside we have pantiles ( a couple bounced off my car as I was gutting out the old bathroom)

No problems with any of the timber frame or insulation side of the build.

[Space Race]

11 minutes ago, twice round the block said:

Re-done the bathroom on our 90's build one.

On the outside we have pantiles ( a couple bounced off my car as I was gutting out the old bathroom)

No problems with any of the timber frame or insulation side of the build.

I can see this in our future What layers were between the main timber frame and your plasterboard? Lining of some sort plus battens?

[ProDave]

Yes you do not want to fill the cavity between the timber frame and the masonry skin.

 

In a TF all the insulation is within the frame, or more recently a layer of insulation over the inside of the frame (you won't have that in a 90's house)

 

There is usually but not always a vapour membrane over the frame before the plasterboard goes on.

 

What does the EPC say?  i.e.what assumptions has the assessor made?

[Space Race]

Re the EPC The walls element is described as "Solid brick, as built, insulated (assumed)" with a 4 star for the energy efficiency and environmental. 

  

[Space Race]

Managed to get a copy of the original plans, I can make out most of the text from the copy but not all hence the odd question mark. Anything to be concerned about here? Thanks

 

Concrete strip foundations all as per foundation layout of drawing Min 450mm below ground level taken down to hard load bearing ground.

Walls to be finished externally with grey granite chip roughcast on 215mm dense concrete blockwork apart from from corners on front elevations which will have natural stone. Internally walls to have 25mm cavity 80 x 38 posting at 400mm ctrs between top and bottom runners with one row intermediate dwangs clad with 9.5mm foilbacked plasterboard with (???) laping and plasterstrim(?) at joints. 51mm expanded polystyrene insulation between posts. 100 x 28.. wallplate over d.p.c at wallhead level.

215mm r.c lintols over all openings. all lintols to have min 150mm hold each. Bit?????? felt d.p.c laid on scarcement with 100 x 25mm wallplate over. 100mm honey????? dwarf walls built off concrete strip foundations 300mm wide, 150mm deep, 150mm deep. 100 x 25mm wallplate over d.p.c allow for creep holes.

Window cill to have d.p.c at back, ends and underside.

Horizontal felt d.p.c incorporated into external wall construction min 150mm above ground level.

[ProDave]

80 by 38 studs is a bit skinny and only 51mm (read that as 2 inch) polystyrene insulation in the frame.

 

It's certainly not the best but at least something.  That's Taping and filling, usual method in Scotland, you just fill then sand the joints on a dry lined wall.

 

If you want to upgrade it, I would suggest over boarding with insulated plasterboard if you can stand a slight reduction in room sizes.

 

Contrast that with our 2003 timber frame with 150mm studs and 150mm rockwool insulation filling the frame.

[Space Race]

7 minutes ago, ProDave said:

80 by 38 studs is a bit skinny and only 51mm (read that as 2 inch) polystyrene insulation in the frame.

 

It's certainly not the best but at least something.  That's Taping and filling, usual method in Scotland, you just fill then sand the joints on a dry lined wall.

 

If you want to upgrade it, I would suggest over boarding with insulated plasterboard if you can stand a slight reduction in room sizes.

 

Contrast that with our 2003 timber frame with 150mm studs and 150mm rockwool insulation filling the frame.

Thanks and yes, 80mm does seem slim. Looking forward we would def want to improve the insulation. 

 

The block is called of as 215mm on the original drawings but during alterations the engineer noted this as 140mm block. I'm aware a 140 block comes as 215 high but would not have expected height to be called off on a drawing over width. That said, I find it hard to imagine the intention was to use a 215x215 block

 

My other concern is the 25mm cavity on a timber frame structure  

[Space Race]

Been researching further and 50mm seems like a minimum for cavity of this type by current standards. Any thoughts on how problematic such a small cavity might be in the future?

[Iceverge]

It's there to ensure the airflow to allow the framing to dry to the outside. 

 

I think 50mm is normally specced as a minimum with external clockwork just to give a greater allowance for any mortar droppings. 25mm is fine from a ventilator perspective and it is lightly any big problems would already have made themselves know.

 

215 block externally may have been the originals plan. As the timber frame has no sheathing it's possible the engineer was counting on the external wall for racking strength. Maybe @Gus Potter would be more knowledgeable. 

 

As for insulation like @ProDavesays insulated plasterboard is probably the easiest win. Worth costing this I would say. 

 

 

[Gus Potter]

On 02/01/2023 at 11:10, Space Race said:

I’m looking for any advice regarding buying an older timber framed house.

Here a few thoughts, please excuse the spelling / grammer as "off duty".

 

@ProDave Enjoyed reading your input, great points and observations you make.

 

I'll try and add a bit where I can maybe fill in some gaps for you.

 

But first there are a couple of pedantic thoughts do you really have a 1990's TF.. lets clear that up first.

On 02/01/2023 at 11:10, Space Race said:

The outer leaf is 140mm concrete block with render whilst the inner is timber framed.

The 140 block flags up.. normally it would be 100mm thick for a UK TF.

 

On 04/01/2023 at 14:47, Space Race said:

Walls to be finished externally with grey granite chip roughcast on 215mm dense concrete blockwork apart from from corners on front elevations which will have natural stone. Internally walls to have 25mm cavity 80 x 38 posting at 400mm ctrs between top and bottom runners with one row intermediate dwangs clad with 9.5mm foilbacked plasterboard with (???) laping and plasterstrim(?) at joints. 51mm expanded polystyrene insulation between posts. 100 x 28.. wallplate over d.p.c at wallhead level.

Forgive me if I sound a bit odd / pedantic .. it's just that there seems some discrepancy in the description of the thickness of the blockwork. I know you have probably copied what you can from the old drawings.. but what flags up and this is why I'm asking is the cavity thickness 25mm. As a minimum it should be 50mm for TF. The EPC also seems to suggest that you may not have a real TF?

 

@Space Race In Scotland we have the home report system. There are good and bad bits about this.. I could write at length.. for another day. But basically they are so heavily caveated that they don't provide the info you need to make a reasonably informed offer., a big hole is a real consideration of how onerous the maintenance requirements may be for example. Tenement flats are worse so be glad you have the info you have. But you also need to cut the surveyor a bit of slack.

 

Anyway.. I may be wrong but have been "pedantic"  as best to ask the daft questions now rather than suffer later.

 

Ok my thoughts are.. do you really have a TF of do you have a more traditional type of construction.. solid walls strapped on the inside. It is not unkown.. folk used to take a solid wall construction, mitigate for vapour / condensation and strap and line. If you are say in the NE of Scotland.. there were a lot of folk who had grown up in solid granite houses.. they wanted something just as robust but a bit warmer.. hence a cavity and an insulated TFnon load bearing lining.

 

Say that is what you are looking at.. then make another visit and look carefully for cracks / sloping floors etc.. post here what you find. In the round though if you do have some form of solid wall construction (the blockwork does the structural heavy lifting and resisting the big winds you get in the NE of Scotland) then it is not a bad thing.

 

If you do have a TF then the good news is that it is probably very drafty (less chance of rot setting in) maybe has 75 -100 mm of glass wool between the studs. The studs could be 89mm x 38mm .. that is a Canadian lumber size, they may be 95 x45.. UK metric graded size or they may have just used ungraded 100 x  50 as this can work too. I can speculate but.. little point at this stage.

 

In the round though if it is a solid wall construction it probably makes it easier to upgrade to a modern standard.

 

Post more if you can and we'll all chip in.

 

Ok you are thinking about offering on this house. What are the risks? If it has stood since the early 1990's then the skeleton is probaby robust enough? If you are a Build Hubber and going to gut the place then actually the solid wall may turn out to be a bonus once you get to air tighness, insulation detailin and running the services you want.

 

Best thing to do is post a few photos / more of your thoughts, provide a bit more info and we will all keep chipping in.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Space Race]

20 hours ago, Iceverge said:

 

I think 50mm is normally specced as a minimum with external clockwork just to give a greater allowance for any mortar droppings. 25mm is fine from a ventilator perspective and it is lightly any big problems would already have made themselves know.

 

Thanks Iceverge. I could not find discussion on any minimum cavity needed solely for airflow. I was aware of the possibility of mortar droppings (+ many other things) bridging the cavity and that might still be a concern in the future, Alterations, Wildlife etc It wouldn't take much with just 25mm  

[Space Race]

 @Gus Potter 

 

Thank you for your thoughts, Much appreciated

 

Whilst we would have more long term plans for the house (build hubbing being addictive), Is is presented in a ready to move into state and we wouldn’t be in a position to carry out work in the short term. When that time came I’d like to think we’d be funding an extension / additions rather than fixing some flawed construction design or ticking time bomb for want of a better term.

 

Another visit is not possible at this time but we did not notice any sloping floors or cracks. That said, Cracks could have been repaired.

 

We are still trying to confirm what the construction type is but I do have a couple of Q’s for either possibilities

 

If a UK T.F might typically be 100mm, Would 140mm not be on the slimmer side for a solid wall construction? More risk of penetration?

 

Any other thoughts on why the change from 215mm (orig plans) to 140mm block might have occurred?

 

So if it is T.F you’d expect nearer 100mm block with a 50mm cavity and If it’s solid wall you’d expect nearer 215mm walls and the T.F (Non load bearing) Is a bonus.

 

How do we feel about a 25mm cavity on a 140 block solid wall construction?

 

Edited January 9, 2023 by Space Race

[Iceverge]

@Space Race

 

Is there any way you can get a look inside the walls? At meter boxes, broken plasterboard etc?

 

If not perhaps just measure the overall thickness of the wall as accuratly as you can at a window or door opening. 

 

I hadn't thought of it as @Gus Potter suggested. A solid walled house with a TF inside just to provide insulation. These days the TF takes the loads of the house and the blockwork is largely there as a rainscreen. 

 

For my own interest I put the original spec into Ubakus for a gander. It's unlightly to perform anywhere near this as the aeroboard is unlightly to be a tight fit. 

 

 

 

 

If you were to go room by room refurbing, pull out the EPS, and replace with PIR cut and foam in place.

Then add a taped vapour membrane. 

Then a 45x45mm counter battened service cavity with 0.035W/mK mineral wool infill and 

15mm plasterboard

 

You could have something like this.  Much more respectable in comfort and energy terms. Tons of work however. 

 

[Space Race]

Thanks Iceverge, I'm not familiar with these results so will need to do further research. Unfortunately it looks like the 215mm block is in fact a 140 which I assume would throw things off 

[Iceverge]

On 09/01/2023 at 17:45, Space Race said:

Thanks Iceverge, I'm not familiar with these results so will need to do further research. Unfortunately it looks like the 215mm block is in fact a 140 which I assume would throw things off 

 

No, I'll be the same regarding insulation. concrete thickness makes almost no difference to the heat loss value and none when there's a ventilated cavity inside it. 

[Nick Thomas]

My previous house is an 80s timber frame in Scotland. Someone with no sense at all had installed blown CWI; this wasn't evident in any of the documentation or from regular surveys, so we were all a bit surprised when we started taking down walls. Dunno how feasible it is to rule that out before buying - it's all kinds of risk, and AIUI mortgage companies won't lend on a TF that's got CWI in it.

 

The previous owners had installed underfloor (the TF is "suspended" - up on stilts - so there was a big crawlspace below it)  and internal PIR insulation, pretty much as detailed above. This seemed fine, but the roof (open to the rafters) was uninsulated and lost heat at an exciting rate. Worth checking what yours is, if it's got a roof space you're probably in a much better position!

 

 

Edited January 11, 2023 by Nick Thomas
s/suspendend/suspended/

[SteamyTea]

On 09/01/2023 at 17:20, Iceverge said:

hadn't thought of it as @Gus Potter suggested. A solid walled house with a TF inside just to provide insulation. These days the TF takes the loads of the house and the blockwork is largely there as a rainscreen

You have to be careful with this construction as any joist/roof truss ends may be susceptible to condensation, especially if any extra internal insulation moves the dewpoint.

Edited January 11, 2023 by SteamyTea

[Space Race]

Both good points. Will update once I know more

[Space Race]

Just to follow up (better late than never!)

 

Gus Potter was spot on, It's a solid wall construction with a small gap and then a timber stud frame with insulation. Apparently this is very common in this area. All moved in and enjoying the new home. Thanks to everyone who pitched in with their thoughts.