Timber frame options for new build, how to decide?

E

ellaoibhe

Registered User
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Other half and I are hoping to commence construction on our new home, 2,500 sq ft story and a half, in the coming months. We've pretty much decided that we want to go down the timber frame route, and self build the rest, by subbing out the various trades. We've received quotes from 5 timber frame companies which all very greatly, and are discovering how little we really know about the whole process. Our aim is to build as warm and energy efficient a home as possible, within the budget that we have to spend. Receiving the various quotes for the timber frame has left us more confused than ever. I'm hoping some of the many knowledgable aam contributors might be able to provide some guidance:

We need to decide between open and closed frame. There's a significant cost difference between the two, but would the extras that are included in the closed frame mean that by the time we have done all the extra work to the open frame system, installed the insulation etc, the price differential might not be so much? Can we achieve the same levels of airtightness and insulation using the much cheaper open panel system by doing the work ourselves? Would love to hear from anyone who has built using either system and opinions on the advantages/disadvantages of one system over the other.

Could anyone provide me with a basic guideline as to how much extra needs to spent to finish the house once you've paid for the timber frame kit to be erected? I know its like asking how long is a piece of string and depends greatly on finishes etc, but even a ballpark figure for things like the blockwork, roofing, plumbing, electric, 2nd fix carpentry etc would be great.

Our big issue is, we know how much we have to spend, and before we can make a decision on which tf co to go with, or which package, we need to know that say for eg our tf costs us 50k, the 120k that we have left will be enough to complete the house (have just used these figures as examples).

Please excuse my lack of knowledge on building issues, I'm on a very steep learning curve here, and as a long time lurker on aam I know there are lots of very informed and experienced contributors who might be happy to share their knowledge and experience.
 
I am familar with timber construction but not an expert.

You may find this is a useful over view from Trada

[broken link removed]

My concern with timber framing and dry wall construction is that it is intrinsically less robust than blockwork.
It does offer potentially good insulation levels, but needs additional sealing and moisture control membranes which can be expensive.

However the level of insulation can vary with built work and the sealing of the frames can be hit and miss on site.
Its very hard to properly seal them unless the work is very well supervised and no redone work occurs, disrupting the seals.
The benefit is that the seal can be "continuous" and workers on site can remedy defects or errors.

The factory production assembly method causes me some concern in relation to "where the bits join".
You are always concerned with a friable material that it could be exposed to interstitial condensation and dew point difficulties.
These may be exacerbated by the high level of sealing the prefabricated components achieve.

I have seen the effects of subsidence and poor construction over time on many buildings.
The higher level of technology used in timber buildings suggest that the phrase "when she was good she was very good, but when she was bad, she was horrid!" may hold true.
This is particualrly so in relation to stopping the passage of cold smoke and fumes through MVHR systems as well as preventing fire propagation through cavities between floors.

Building it in block with external HD insulation is not necessarily the answer either.
Has anyone asked, never mind answered what would happen if one of these externally insulated houses catches fire?
What stops it going up like a ball of flame?

So yes there are a lot of informed people here and yes, we are quick studies in general, but IMO we're only beginning to learn about timber frame.
New products that cure everything from interstitial condensation to breathign difficulties to air filtration and CO2 reduction appear every day.
With building, you need an extended feedback loop over time, just like in the Pyrite in Foundation debacle.
Potential problems are sometimes not immediately apparent until something bad happens.

No doubt others will contribute to this thread.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
Thanks for taking the time to reply. Just to explain a little about our reasons for deciding to go for TF, We had originally planned to build using block, but the more we researched and read the more we realised how little we know in terms of building an energy efficient house, insulating it to beyond the basic current regs, dealing with things like cold bridging, thermal looping, interstitial condensation and all those other buzz words which we've come to be so familiar with but actually know next to nothing about. Just when I think I've got a handle on something, I read something else that confuses me further. It seems that if you have a problem called x, then y is the solution, but when you apply y that has an effect on z so you need to do something else and on it goes. We could just sub out all the trades, we know plenty of less than busy plumbers, blocklayers etc and let them slap up the house for as little as possible (we've already had lots of eyes rolled up to heaven from a builder family member who thinks we're just on a mission to waste money with all these modern "fads") as so many people we know have done but we made a conscious decision that we really want to do this as well as possible, its our third and last home. On the other side of that is the reality that the budget is the budget, we have what we have and we have no more so thats it. Alot of people on various forums recommend people to find yourself a builder who is familier with current regs and modern methods but thats easier said than done. We both have to work full time to pay for all of this, so even if either of us were experts in building we couldnt be on site enough to ensure that the various trades were carrying out their jobs to the standard that we want, particularly in terms of airtightness and insulation which I understand can be tricky enough in a blockbuilt house unless you know what you're doing. We did look into the possibility of building block and then externally insulating on the recomendation of our architect however the cost was prohibitive. And reading what you've said above I'm glad that we did. So weighing all of that up is what brought us to the decision to go timber frame, although I'm not so sure now having read your post ONQ! If you had to choose, what would be your chosen method of building?
 
we are also looking at getting a t frame house built this year,the main reasons are -easier to get airtight,cleaner build and easier when its the direct labour route.We know there are pros and cons to all building methods but it's our preference.When we mention to people we are going t frame they all have told us not to but none of them can give a valid reason.

We also got 5 quotes and it took a long time to go through them as they were so different in spec.we have ruled 3 out,one was too far away and just got a bad feeling about them,another because of lack of detail(type of insulation,roof u values)and another because of their use of a certain rigid insulation which is not certified so cant be sure of u values.we are down to two which use the same methods and are the same price,it's just up to us now who we prefer.Both are using the closed wall with service cavity,cellulose insulation and very close u values to each other.
 
Hi samm, would you mind sending me a pm with the names of the tf companies you've been dealing with and your experience of them? It would be a great help to hear from someone who's a little further down the line. Our reasons for building TF are very similiar to yours, and also have had to deal with people telling us that block built is best but no-one able to back it up with any valid reasons.
 
Hi guys,

Every method of building has its pros and cons and I outline a few of them hereunder for your consideration
The conflicting reviews point towards the only real solution - a balanced, knowledgeable approach by someone who knows what he's doing.
I don't dislike timber frame - I am just doing what I usually do - making people aware of some of the pitfalls before commenting in a more balaced fashion.
In the piece below "Interstitial" = "within the construction": can refer to materials or cavities or services.


General Comments

That being said I am a great beleiver in Rockwool insulation.
Mineral Wool is inherently fire resistant as oppsed to hydrocarbon-based products.
It offers useful soundproofing if used internally.
It is not as high tech or efficient per mm width.
It should not be "packed tight" thinking this gives more thermal insulation - it doesn't.

You can includefire rated hoods for recessed downlighters.
You can follow the line of the roof if you want to convert the attic.
You can include proprietary insulation/cavity closers around opes and at tops of wall cavities.

MVHR

You can include fire rated seals for the ventilation system.
This solution needs more work for the cold smoke and fumes though.
Also there is a huge sound transmission problem with some systems room-to-room.


Masonry construction:

Externally insulating buildings has been the subject of several articles by Joe Little architect over on Construct Ireland.
Their website is a fund of information.
Here are some tips regarding retrofit, which can equally be applied to masonry new build:
[broken link removed]

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Internally super insulating with a foil of other one way vapour check can cause the dew point to occur within the inner leaf or on the face of it, leading to a build up of moisture and smells.
Using a Variable Vapour Check can allow moisture built up under certain circumsances to migrate back into the room and be vented using the ventilation system.
This can work to reduce moisture overall over time and improving insulation.

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Using cavity beads can be a hit and miss affair.
You can only really check where they landed or if they fully filled the cavity by taking out a brick or drilling.
You can remotely sense this using a heat imaging sensor to give a colour coded photo.
Without either review you just won't know whether the beads are in the right place.

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A client of ours did a belt and braces internal insulation within rooms and beaded cavity insulation with a MVHR system.
He achieved A3 on a 6,000 sq.ft house. A lot of it was bungalow with rockwool insulation for the roof sections.
Fingers crosses = looks good [and keeps him warm] so far.


Timber Frame Construction

I think we're seeing some problems with under specced construction members on large rooms leading to deflection and sound transmission.

Deflection needs intermediate steels or bigger members.
Impact noise needs resilient materials under the floor on the tops of joists.

Overloading/underspeccing can occur in an otherwise well-speecd house by people deciding at a late stage to include 1st floor Under Floor Central Heating [UFCH] and simply adding the weight of screed + water in pipes to an existing floor structure.

Many timber framed houses are actually reinforced by steel members at points of load concentration. Not usually a problem internally, they can still attract moisture and cause problems if exposed to a cold cavity.

In a super insulated house, you may find that timber, while GOOD, is not perfect as an insulator. You cannot get away with less than perfect detailing in such buildings or local cold bridging may occur in materials you thought would never be affected.


Sealing, Generally

Assuming you have insulated the building envelope, air movement through the house causes most heat loss.

Sealing the envelope reduced infiltration gains, but places an increased onus on homeowners to ventilate roooms to maintain air quality. When its colder outside than in, the only way to do this while economically maintaining inner temperature is to use a heat exchanger in a mech-or-naturally vented system.

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Open fires or gas appliances need proper supply air, which defeats the purpose of sealing, so you need sealed fires with special supply and extract air arrangements.

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Lobby approaches are required both front and rear to maintain a limited exchange of air as people enter and leave the dwelling on cold days - imagine front and rear doors open at the same time - all the heat goes out the doors!

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People are beginning to understand the benefits of sealing insulation in cavities or roofs where the wind pressure can affect the interstitial spaces. Basically there is no point insulating something if a force 8 at minus 1 degree C can get in around it and freeze the face of what its supposed to be insulating.

Weathersealing the outer face of the insulation and preventing "looping" in cavities is the key - this level of building physics is still being discovered, but it points the way to why some well insulated houses may not be achieving ther standards expected of them.


Services and Fixtures, Generally

People seldom consider them in these ways, but service runs breach both fire sealing and vapour checks in walls. Timber frames detailing can address this by adding a service cavity, with the vapour check behind it and filling the service cavity it with rockwool to improve insulation overall, maintain heat in pipes and minimise interstitial consdensation build up.

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People fail to consider the amount of heat lost by using sinks and bathrooms. Never mind the MVHR, we urgently need a waste water heat reclamation system for water from sinks, showers and baths - not toot sure about the loo!

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People should consider a water reclamation system for use for flusing water for cisterns and a rainwater collection system.

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This isn't an exhaustive list and others may have their own preferences and hopefully they'll post them here for your consideration.

HTH

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
Hi Ong,

Just on mhrv,have you evercome across any one using dcv instead,a lot less ducting around house,just in kitchens and bathrooms and low wattage motor?
 
samm said:
Hi Ong,

Just on mhrv,have you evercome across any one using dcv instead,a lot less ducting around house,just in kitchens and bathrooms and low wattage motor?
Click to expand...

Some questions I was considering:

Where does the air come from in DCV, how is it introduced into the space, heated, heat reclaimed.

Some additional questions on ventilation:

What are the dangers of not ventilating interstitial spaces that are closed up?

I had a long answer written but Firefox dumped me when I tried to access the WIkipedia page on Mold (Mould) problems.


ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
Very strange. Just been dumped three times by a page on Wiki dealing with toxic mould.

I've removed the link. Looks like its a permanent fault.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 

My posts can be a bit much to digest, so I'll draw your attention to this.

There are requirements for fire resistance for elements of structure and between ground and first floors and between house and garage.

Does their design meet these requirements?


ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
Yes onq your posts are a bit much to digest, but please keep them coming as you've told me more in a few posts than my architect has in the 6 months that we've been dealing with him. We'll be spending the weekend reading through everything as well as trying to make sense of the various specs offered by the tf companies that we've gotten quotes from.
 
LOL!

Many thanks (I think) ellaoibhe!

That is the difficulty - a little knowledge is a dangerous thing but even briefly covering a subject like ventilation reads like a treatise.

Unfortunately my experience with some members of my profession is that while they are good designers of form, using light and materials, they do not pay enough attention to their detailing and building physics.
Ironically this lack of familiarity with the nuts and bolts is what frees up their minds to be good designers, but you wouldn't let some of them near a set of working drawings.
Ergo, the growing dependence of some offices on architctural technicians beyond the support they would normally provide.

For my own part, I have spent the past three years or so reading the latest research and trying to anticipate possible pitfalls, adding to my own store of knowlede in the process.
Its still not perfectly clear what all the implications for are for our growing understanding of insulation and building physics but discussing them openly in a forum like this cannot be a bad thing.
Comments by peers are invited and expected and words of experience from self-builders are welcomed and offer an empirical research counterpoint to balance the theoretical academic reasoning.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
(chuckle)

Don't worry ellaoibhe, I know exactly what you mean.

Sometimes I see my older posts and wonder:

"Did I really write all that?"
 
hi ellaoibhe,
I amjust about to finish my 3000 sqft timberframe direct labour build and would be glad to answer any questions if i am any use to you.
To answer your question. I built a A2 rated home and utilized hrv solar and airtightness.
The fame versus finish cost was 25 percent. I.E. 70K frame over 280K home. The frame included all insulation (cellulose and rockwool) airtigh membrane and guaranteed airtightness test on completion.
I turned on a dimplex heater in november before the oil was turned on during the cold spell and the 3 kw heater was able to heat the home.
move in date will be easter.
 
God pjmcke, I'd say I have tons of questions for you! Thats exactly the kind of info i'm looking for. Would you mind sending me a pm with the name of the tf company you used? Also, I'm guessing that at that price you went for a closed panel system? What part of the country are you building in? Thanks in advance!
 
pjmcke, samm
could you send me on the TF companies you looked at for prices as well please
 
+1 what alser has posted.

Make sure you obtain at least three prices based on competently prepared tender documents and involve an architect.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
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