Tex. Property Code § 22.021

(a) A defendant in a trespass to try title action who is not the rightful owner of the property, but who has possessed the property in good faith and made permanent and valuable improvements to it, is either:

(1) entitled to recover the amount by which the estimated value of the defendant's improvements exceeds the estimated value of the defendant's use and occupation of and waste or other injury to the property; or

(2) liable for the amount by which the value of the use and occupation of and waste and other injury to the property exceeds the value of the improvements and for costs.

(b) In estimating values of improvements or of use and occupation:

(1) improvements are valued at the time of trial, but only to the extent that the improvements increased the value of the property; and

(2) use and occupation is valued for the time before the date the action was filed that the defendant was in possession of the property, but excluding the value resulting from the improvements made by the defendant or those under whom the defendant claims.

(c) The defendant who makes a claim for improvements must plead:

(1) that the defendant and those under whom the defendant claims have had good faith adverse possession of the property in controversy for at least one year before the date the action began;

(2) that they or the defendant made permanent and valuable improvements to the property while in possession;

(3) the grounds for the claim;

(4) the identity of the improvements; and

(5) the value of each improvement.

(d) The defendant is not liable for damages under this section for injuries or for the value of the use and occupation more than two years before the date the action was filed, and the defendant is not liable for damages or for the value of the use and occupation in excess of the value of the improvements.