House built in solid construction with a gable in timber framing

Hello,

the planning for our construction project is progressing rapidly. Now we received the following suggestion from the carpentry company that is supposed to carry out the roof: From their point of view, it would be advisable to execute the gable sides of our staggered shed roof as a timber frame structure, because overall

a) it would be structurally simpler and
b) it would bring advantages in terms of thermal bridge freedom.

The house is otherwise planned as a solid masonry house with 36.5 cm masonry. According to the current plans and calculations by the energy consultant, we will achieve KfW55. Nevertheless, we are of course open to anything that would bring further advantages in energy efficiency. From the simpler construction one could also deduce that it might ultimately be cheaper.

My concerns are mainly about crack formation in the facade due to different thermal expansion of the materials used. This will always be the case to some extent, but I could imagine that the effect would be more noticeable if everything above the upper floor ceiling is made of wood.

It might also be important to mention that the space between the upper floor ceiling and the roof is only to be used as a storage room. Insulation will still be installed over the roof surfaces, so the room is within the insulation layer.

Are there any experiences or reasons for or against such an execution regarding this topic?

Thank you very much and best regards Holger

Hello Holger,

we once looked at such a "Hybridhaus" that was for sale.

In fact, we discovered an almost continuous, clearly visible cracking at the transitions from the masonry to the timber-framed building section, both inside and outside.

The house was only three years old at the time of the viewing.

However, I am not an expert in building damage – I am sure a number of others will chime in here.

Regards,

Dirk

Hi,

well, I have never seen that only the gables are built in timber frame construction. I can well imagine that what Doc Schnaggels says is true and what reinforces your concerns: Whether that is really the best solution, one might initially have some doubts.

Construction took place in the immediate neighborhood: solid on the ground floor, the upper floor then in timber frame construction. My father and I have a similar house in Hesse, ground floor masonry, upper floor Swedish log house. But that is something different than just gables.

If the suggestion came afterwards, the thermal bridges must have already been successfully calculated with regard to gables in solid construction. So: where is the advantage then, the house is already planned as KFW-55 anyway.

Best regards
Thorsten

Hello Holger,

Now there was the following suggestion from the carpentry company that is supposed to carry out the roof: From their point of view, it would be advisable to construct the gable sides of our offset shed roof as a timber frame, because overall

a) it would be structurally simpler and
b) it would offer advantages in terms of thermal bridge freedom.

I rather see it so that only the order volumes present themselves more positively for the carpenter.

I know 2 providers who work like this or similarly; the purpose of this mixed masonry has not yet become clear to me. One generally builds the gable walls in the attic fully, the second only the inner shell (including knee wall) in lightweight construction; ground floor and every further full storey generally massive.

According to the current plans and calculations of the energy consultant, we achieve KfW55.

And why do you then want to spend money again for possibly statics but certainly thermal protection verification?

Rhenish greetings

Thank you very much for the answers.

I have now also given some thought to the possible advantages and am still uncertain. The short vertical section between the two shed roofs will in any case be made of wood, so theoretically there would be even one less material change. The energy consultant has meanwhile confirmed that the measure would of course have positive effects on the transmission heat losses. Since we will achieve our goal anyway, the question of necessity is of course justified. The structural engineer has also already commented on this: with a timber frame construction, the ring beam can be omitted. So there are indeed constructive advantages. The question remains whether such a construction would potentially be more prone to cracking from the plasterer's point of view (whom we unfortunately do not have yet).

It will probably be best to compare the expected costs for both variants and, in the event that there is no cost advantage for the mixed construction method, to stick with the tried and tested. I will definitely get back to you once the costs are clear.

Thank you very much and best regards