Profiled wood or plastic profile boards above the rafters?

Hello dear forum,

we are currently planning our single-family house. It will be 1.5 stories with a gable roof.

For aesthetic reasons, we would like visible flying rafters and profiled foot, middle, and ridge purlin heads. The roof structure should be made of structural solid wood.

We already have two offers for this. However, they differ in the visible cladding above the rafters.

One provider says that only profiled wood makes sense here (and apparently he cannot do it differently), since these then lie on the rafters but below the roof battens. Otherwise, he would not give a warranty. The expansion behavior regarding plastic would be too different, so that in the case of plastic profile boards these might possibly break.

The other provider, however, offers plastic profile boards as standard.

Due to less maintenance over the years and without weather effects, the plastic profile boards actually seem more convincing to us. It is certainly also cheaper than investing in expensive paint every few years.

What surprises us is that the first provider generally rejects this from a construction engineering point of view and believes that it is technically not possible. Does the second provider perhaps build differently and master newer methods?

We would be very happy about opinions and experiences.

Best regards Riepirat

Hello Riepirat,

I can’t help you with the technical differences between plastic profile boards and profile timber.

Our roof overhangs - even with visible purlins and rafters - are clad with profile timber - both the plastic claddings (which I mentioned) were strongly discouraged by both the house manufacturer and the architect because of the different expansion behavior of wood & plastic that you mentioned.

We solved the problem of the more frequent effort regarding paint by not staining the visible wood but painting it. It won’t last forever either, but it certainly has a much longer lifespan than a "normal" stain.

However, I have a completely different tip for you:

If you are actually building with partially visible rafters and purlins, I would recommend equipping the top sides of the visible purlins (in areas where no rafter lies on them) with bird deterrent spikes while the scaffolding is still up. This is possible without much effort, even for a layperson (attaching the spike strips with roofing nails - the spike strips can be cut to the required length with a decent pair of pliers (side cutter)).

We didn’t think of these spikes and were then surprised by the numerous kestrels in our area, which apparently felt very comfortable on our purlins and decorated our windows directly below almost daily with unwanted "Model flying dinosaur poop" decorations. Occasionally, half-eaten mice also stuck to our French balconies.

Since attaching the spikes afterward, it has been quiet again - the dear birds now rather sit comfortably on our wood shelter and conveniently deposit their "output" somewhere else...

Regards,

Dirk

Hello Dirk,

thank you for your detailed and also amusingly written report of experience regarding the bird problem. It really reads very well!

The idea of painting is a good one, which we should definitely consider in the case of wood.

The idea of bird deterrent spikes is also a good one and I will immediately add it to our long list. We had already spotted it during a walk through a new housing development, but at first we didn’t think much of it. But as long as the scaffolding is up, the effort is actually manageable.

Regarding the profile boards, the argument about the expansion behavior seems to be well known. I am only surprised that plastic profile boards are increasingly seen in new housing developments. Either the installers of plastic profile boards seem to lack knowledge, or it is accepted that the customer might have problems with them, or they have more knowledge about this and possibly use a different technique to avoid the possible expansion problems.

This question is therefore still open.

Best Regards, Riepirat