On the Nikon Cameras, the best setting for NON Moving objects ( buildings, flowers, Macro, Portraits) will be the AF-S mode.( Singe Focus Mode)

The camera will lock onto a single object and remain focused until the finger is released. result will be a sharp Picture.

From previous experience, I have noticed that the Nikon Cameras are set to AF-A as a default.

This although a great all round focusing method, is not a dedicated Single Area Focus Method because it relies on the onboard computer to determine if there is anything moving in the frame. If there is, say a bird, or a slight movement of your hand, it will change to the AF-C Mode (used for moving Objects) and this can sometimes throw off your focus slightly and give you that slightly blurry image compared to a very sharp image.

Other areas that I pay special emphasis on when taking photos of buildings are as follows;

Tripod or beanbag on a wall.

I also tend to shoot such subjects with the self timer to avoid any camera shake, that is if I don’t have a remote release.

Sometimes I may even lock the Mirror, specially if it is Macro shooting where there is a greater chance of camera shake.

I always pick the focus point manually. When you view the dots through the viewfinder, set manually the area you want to be your main focus.

I also ensure that I use an Aperture where I have everything in focus based on the dept of field. Generally f8.0 or higher.

If I have to use the camera in hand and not on a tripod, then the shutter speed is very crucial, even if that now means that the ISO has to go high.

As a minimum, I will ensure that my shutter speed is always slightly higher that the focal length of the lens. If I am shooting with 200mm lens, then I ensure that my shutter speed is higher than 200sec.

You can also set a back button button for focusing, and also play with different stances for handholding. Left hand over your right bicep creates a very solid platform to rest your camera on and can help create steady shots

If none of the above improves your pictures, then there could be back/front focusing issue. You may need to check out how to on Youtube of your camera. It is a simple process and will help

Please also note, Trees can also sometimes make an image look a little blurry if it is a slight windy day. Cure; higher shutter speed or wait till the wind drops.

Hope this help and good luck